diff mbox series

[v4,15/18] dt-bindings: usb: Add ports to google,cros-ec-typec for DP altmode

Message ID 20240901040658.157425-16-swboyd@chromium.org
State New
Headers show
Series platform/chrome: Add DT USB/DP muxing/topology support | expand

Commit Message

Stephen Boyd Sept. 1, 2024, 4:06 a.m. UTC
Add a DT graph binding to google,cros-ec-typec so that it can combine
DisplayPort (DP) and USB SuperSpeed (SS) data into a USB type-c endpoint
that is connected to the usb-c-connector node's SS endpoint. This also
allows us to connect the DP and USB nodes in the graph to the USB type-c
connectors, providing the full picture of the USB type-c data flows in
the system.

Allow there to be multiple typec nodes underneath the EC node so that
one DT graph exists per DP bridge. The EC is actually controlling TCPCs
and redrivers that combine the DP and USB signals together so this more
accurately reflects the hardware design without introducing yet another
DT node underneath the EC for USB type-c.

If the type-c ports are being shared between a single DP controller then
the ports need to know about each other and determine a policy to drive
DP to one type-c port. If the type-c ports each have their own dedicated
DP controller then they're able to operate independently and enter/exit
DP altmode independently as well. We can't connect the DP controller's
endpoint to one usb-c-connector port@1 endpoint and the USB controller's
endpoint to another usb-c-connector port@1 endpoint either because the
DP muxing case would have DP connected to two usb-c-connector endpoints
which the graph binding doesn't support.

Therefore, one typec node is required per the capabilities of the type-c
port(s) being managed. This also lets us indicate which type-c ports the
DP controller is wired to. For example, if DP was connected to ports 0
and 2, while port 1 was connected to another DP controller we wouldn't
be able to implement that without having some other DT property to
indicate which output ports are connected to the DP endpoint.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc: Conor Dooley <conor+dt@kernel.org>
Acked-by: Lee Jones <lee@kernel.org>
Cc: Benson Leung <bleung@chromium.org>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Prashant Malani <pmalani@chromium.org>
Cc: Tzung-Bi Shih <tzungbi@kernel.org>
Cc: <devicetree@vger.kernel.org>
Cc: <chrome-platform@lists.linux.dev>
Cc: Pin-yen Lin <treapking@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 .../bindings/mfd/google,cros-ec.yaml          |   7 +-
 .../bindings/usb/google,cros-ec-typec.yaml    | 229 ++++++++++++++++++
 2 files changed, 233 insertions(+), 3 deletions(-)

Comments

Lee Jones Sept. 3, 2024, 3:35 p.m. UTC | #1
On Sat, 31 Aug 2024, Stephen Boyd wrote:

> Add a DT graph binding to google,cros-ec-typec so that it can combine
> DisplayPort (DP) and USB SuperSpeed (SS) data into a USB type-c endpoint
> that is connected to the usb-c-connector node's SS endpoint. This also
> allows us to connect the DP and USB nodes in the graph to the USB type-c
> connectors, providing the full picture of the USB type-c data flows in
> the system.
> 
> Allow there to be multiple typec nodes underneath the EC node so that
> one DT graph exists per DP bridge. The EC is actually controlling TCPCs
> and redrivers that combine the DP and USB signals together so this more
> accurately reflects the hardware design without introducing yet another
> DT node underneath the EC for USB type-c.
> 
> If the type-c ports are being shared between a single DP controller then
> the ports need to know about each other and determine a policy to drive
> DP to one type-c port. If the type-c ports each have their own dedicated
> DP controller then they're able to operate independently and enter/exit
> DP altmode independently as well. We can't connect the DP controller's
> endpoint to one usb-c-connector port@1 endpoint and the USB controller's
> endpoint to another usb-c-connector port@1 endpoint either because the
> DP muxing case would have DP connected to two usb-c-connector endpoints
> which the graph binding doesn't support.
> 
> Therefore, one typec node is required per the capabilities of the type-c
> port(s) being managed. This also lets us indicate which type-c ports the
> DP controller is wired to. For example, if DP was connected to ports 0
> and 2, while port 1 was connected to another DP controller we wouldn't
> be able to implement that without having some other DT property to
> indicate which output ports are connected to the DP endpoint.
> 
> Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
> Cc: Conor Dooley <conor+dt@kernel.org>
> Acked-by: Lee Jones <lee@kernel.org>
> Cc: Benson Leung <bleung@chromium.org>
> Cc: Guenter Roeck <groeck@chromium.org>
> Cc: Prashant Malani <pmalani@chromium.org>
> Cc: Tzung-Bi Shih <tzungbi@kernel.org>
> Cc: <devicetree@vger.kernel.org>
> Cc: <chrome-platform@lists.linux.dev>
> Cc: Pin-yen Lin <treapking@chromium.org>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  .../bindings/mfd/google,cros-ec.yaml          |   7 +-

Acked-by: Lee Jones <lee@kernel.org>

>  .../bindings/usb/google,cros-ec-typec.yaml    | 229 ++++++++++++++++++
>  2 files changed, 233 insertions(+), 3 deletions(-)
Dmitry Baryshkov Sept. 20, 2024, 9:38 a.m. UTC | #2
On Sat, Aug 31, 2024 at 09:06:53PM GMT, Stephen Boyd wrote:
> Add a DT graph binding to google,cros-ec-typec so that it can combine
> DisplayPort (DP) and USB SuperSpeed (SS) data into a USB type-c endpoint
> that is connected to the usb-c-connector node's SS endpoint. This also
> allows us to connect the DP and USB nodes in the graph to the USB type-c
> connectors, providing the full picture of the USB type-c data flows in
> the system.
> 
> Allow there to be multiple typec nodes underneath the EC node so that
> one DT graph exists per DP bridge. The EC is actually controlling TCPCs
> and redrivers that combine the DP and USB signals together so this more
> accurately reflects the hardware design without introducing yet another
> DT node underneath the EC for USB type-c.
> 
> If the type-c ports are being shared between a single DP controller then
> the ports need to know about each other and determine a policy to drive
> DP to one type-c port. If the type-c ports each have their own dedicated
> DP controller then they're able to operate independently and enter/exit
> DP altmode independently as well. We can't connect the DP controller's
> endpoint to one usb-c-connector port@1 endpoint and the USB controller's
> endpoint to another usb-c-connector port@1 endpoint either because the
> DP muxing case would have DP connected to two usb-c-connector endpoints
> which the graph binding doesn't support.
> 
> Therefore, one typec node is required per the capabilities of the type-c
> port(s) being managed. This also lets us indicate which type-c ports the
> DP controller is wired to. For example, if DP was connected to ports 0
> and 2, while port 1 was connected to another DP controller we wouldn't
> be able to implement that without having some other DT property to
> indicate which output ports are connected to the DP endpoint.

Based on our disccusions at LPC, here are several DT examples that seem
sensible to implement this case and several related cases from other
ChromeBooks.

typec {
	compatible = "google,cros-ec-typec";

	port {
		typec_dp_in: endpoint {
			remote-endpoint = <&usb_1_qmp_phy_out_dp>;
		};
	};

	usb_c0: connector@0 {
		compatible = "usb-c-connector";
		reg = <0>;

		ports {
			port@0 {
				reg = <0>;
				usb_c0_hs_in: endpoint {
					remote-endpoint = <&usb_hub_dfp1_hs>;
				};
			};

			port@1 {
				reg = <1>;
				usb_c0_ss_in: endpoint {
					remote-endpoint = <&usb_hub_dfp1_ss>;
				};
			};
		};
	};

	usb_c1: connector@1 {
		compatible = "usb-c-connector";
		reg = <1>;

		ports {
			port@0 {
				reg = <0>;
				usb_c1_hs_in: endpoint {
					remote-endpoint = <&usb_hub_dfp2_hs>;
				};
			};

			port@1 {
				reg = <1>;
				usb_c1_ss_in: endpoint {
					remote-endpoint = <&usb_hub_dfp2_ss>;
				};
			};
		};
	};
};

&usb_1_qmpphy {
	ports {
		port@0 {
			endpoint@0 {
				data-lanes = <0 1>;
				// this might go to USB-3 hub
			};

			usb_1_qmp_phy_out_dp: endpoint@1 {
				remote-endpoint = <&typec_dp_in>;
				data-lanes = <2 3>;
			};
		}
	};
};

-------

typec {
	connector@0 {
		port@1 {
			endpoint@0 {
				remtoe = <&usb_hub_0>;
			};

			endpoint@1 {
				remote = <&dp_bridge_out_0>;
			};
		};
	};

	connector@1 {
		port@1 {
			endpoint@0 {
				remtoe = <&usb_hub_1>;
			};

			endpoint@1 {
				remote = <&dp_bridge_out_1>;
			};
		};
	};
};

dp_bridge {
	ports {
		port@1 {
			dp_bridge_out_0: endpoint@0 {
				remote = <usb_c0_ss_dp>;
				data-lanes = <0 1>;
			};

			dp_bridge_out_1: endpoint@1 {
				remote = <usb_c1_ss_dp>;
				data-lanes = <2 3>;
			};
		};
	};
};

-------

This one is really tough example, we didn't reach a conclusion here.
If the EC doesn't handle lane remapping, dp_bridge has to get
orientation-switch and mode-switch properties (as in the end it is the
dp_bridge that handles reshuffling of the lanes for the Type-C). Per the
DisplayPort standard the lanes are fixed (e.g. DPCD 101h explicitly
names lane 0, lanes 0-1, lanes 0-1-2-3).

typec {
	connector@0 {
		port@1 {
			endpoint@0 {
				remtoe = <&usb_hub_0>;
			};

			endpoint@1 {
				remote = <&dp_bridge_out_0>;
			};
		};
	};
};

dp_bridge {
	orientation-switch;
	mode-switch;
	ports {
		port@1 {
			dp_bridge_out_0: endpoint {
				remote = <usb_c0_ss_dp>;
				data-lanes = <0 1 2 3>;
			};
		};
	};
};

-------

> Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
> Cc: Conor Dooley <conor+dt@kernel.org>
> Acked-by: Lee Jones <lee@kernel.org>
> Cc: Benson Leung <bleung@chromium.org>
> Cc: Guenter Roeck <groeck@chromium.org>
> Cc: Prashant Malani <pmalani@chromium.org>
> Cc: Tzung-Bi Shih <tzungbi@kernel.org>
> Cc: <devicetree@vger.kernel.org>
> Cc: <chrome-platform@lists.linux.dev>
> Cc: Pin-yen Lin <treapking@chromium.org>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  .../bindings/mfd/google,cros-ec.yaml	  |   7 +-
>  .../bindings/usb/google,cros-ec-typec.yaml    | 229 ++++++++++++++++++
>  2 files changed, 233 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
> index c991626dc22b..bbe28047d0c0 100644
> --- a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
> +++ b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
> @@ -98,9 +98,6 @@ properties:
>  
>    gpio-controller: true
>  
> -  typec:
> -    $ref: /schemas/usb/google,cros-ec-typec.yaml#
> -
>    ec-pwm:
>      $ref: /schemas/pwm/google,cros-ec-pwm.yaml#
>      deprecated: true
> @@ -166,6 +163,10 @@ patternProperties:
>      type: object
>      $ref: /schemas/extcon/extcon-usbc-cros-ec.yaml#
>  
> +  "^typec(-[0-9])*$":
> +    type: object
> +    $ref: /schemas/usb/google,cros-ec-typec.yaml#
> +
>  required:
>    - compatible
>  
> diff --git a/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml b/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml
> index 365523a63179..235b86da3cdd 100644
> --- a/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml
> +++ b/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml
> @@ -26,6 +26,106 @@ properties:
>    '#size-cells':
>      const: 0
>  
> +  mux-gpios:
> +    description: GPIOs indicating which way the DP mux is steered
> +    maxItems: 1
> +
> +  no-hpd:
> +    description: Indicates this endpoint doesn't signal HPD for DisplayPort
> +    type: boolean
> +
> +  mode-switch:
> +    $ref: usb-switch.yaml#properties/mode-switch
> +
> +  orientation-switch:
> +    $ref: usb-switch.yaml#properties/orientation-switch
> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port@0:
> +	$ref: /schemas/graph.yaml#/$defs/port-base
> +	unevaluatedProperties: false
> +	description: Output ports for combined DP and USB SS data
> +	patternProperties:
> +	  "^endpoint@([0-8])$":
> +	    $ref: usb-switch.yaml#/$defs/usbc-out-endpoint
> +	    unevaluatedProperties: false
> +
> +	anyOf:
> +	  - required:
> +	      - endpoint@0
> +	  - required:
> +	      - endpoint@1
> +	  - required:
> +	      - endpoint@2
> +	  - required:
> +	      - endpoint@3
> +	  - required:
> +	      - endpoint@4
> +	  - required:
> +	      - endpoint@5
> +	  - required:
> +	      - endpoint@6
> +	  - required:
> +	      - endpoint@7
> +	  - required:
> +	      - endpoint@8
> +
> +      port@1:
> +	$ref: /schemas/graph.yaml#/$defs/port-base
> +	unevaluatedProperties: false
> +	description:
> +	  Input port to receive USB SuperSpeed (SS) data
> +	patternProperties:
> +	  "^endpoint@([0-8])$":
> +	    $ref: usb-switch.yaml#/$defs/usbc-in-endpoint
> +	    unevaluatedProperties: false
> +
> +	anyOf:
> +	  - required:
> +	      - endpoint@0
> +	  - required:
> +	      - endpoint@1
> +	  - required:
> +	      - endpoint@2
> +	  - required:
> +	      - endpoint@3
> +	  - required:
> +	      - endpoint@4
> +	  - required:
> +	      - endpoint@5
> +	  - required:
> +	      - endpoint@6
> +	  - required:
> +	      - endpoint@7
> +	  - required:
> +	      - endpoint@8
> +
> +      port@2:
> +	$ref: /schemas/graph.yaml#/$defs/port-base
> +	description:
> +	  Input port to receive DisplayPort (DP) data
> +	unevaluatedProperties: false
> +
> +	properties:
> +	  endpoint:
> +	    $ref: usb-switch.yaml#/$defs/dp-endpoint
> +	    unevaluatedProperties: false
> +
> +	required:
> +	  - endpoint
> +
> +    required:
> +      - port@0
> +
> +    anyOf:
> +      - required:
> +	  - port@1
> +      - required:
> +	  - port@2
> +
>  patternProperties:
>    '^connector@[0-9a-f]+$':
>      $ref: /schemas/connector/usb-connector.yaml#
> @@ -35,6 +135,40 @@ patternProperties:
>  required:
>    - compatible
>  
> +allOf:
> +  - if:
> +      required:
> +	- no-hpd
> +    then:
> +      properties:
> +	ports:
> +	  required:
> +	    - port@2
> +  - if:
> +      required:
> +	- mux-gpios
> +    then:
> +      properties:
> +	ports:
> +	  required:
> +	    - port@2
> +  - if:
> +      required:
> +	- orientation-switch
> +    then:
> +      properties:
> +	ports:
> +	  required:
> +	    - port@2
> +  - if:
> +      required:
> +	- mode-switch
> +    then:
> +      properties:
> +	ports:
> +	  required:
> +	    - port@2
> +
>  additionalProperties: false
>  
>  examples:
> @@ -50,6 +184,8 @@ examples:
>  
>	  typec {
>	    compatible = "google,cros-ec-typec";
> +	  orientation-switch;
> +	  mode-switch;
>  
>	    #address-cells = <1>;
>	    #size-cells = <0>;
> @@ -60,6 +196,99 @@ examples:
>	      power-role = "dual";
>	      data-role = "dual";
>	      try-power-role = "source";
> +
> +	    ports {
> +	      #address-cells = <1>;
> +	      #size-cells = <0>;
> +
> +	      port@0 {
> +		reg = <0>;
> +		usb_c0_hs: endpoint {
> +		  remote-endpoint = <&usb_hub_dfp3_hs>;
> +		};
> +	      };
> +
> +	      port@1 {
> +		reg = <1>;
> +		usb_c0_ss: endpoint {
> +		  remote-endpoint = <&cros_typec_c0_ss>;
> +		};
> +	      };
> +	    };
> +	  };
> +
> +	  connector@1 {
> +	    compatible = "usb-c-connector";
> +	    reg = <1>;
> +	    power-role = "dual";
> +	    data-role = "dual";
> +	    try-power-role = "source";
> +
> +	    ports {
> +	      #address-cells = <1>;
> +	      #size-cells = <0>;
> +
> +	      port@0 {
> +		reg = <0>;
> +		usb_c1_hs: endpoint {
> +		  remote-endpoint = <&usb_hub_dfp2_hs>;
> +		};
> +	      };
> +
> +	      port@1 {
> +		reg = <1>;
> +		usb_c1_ss: endpoint {
> +		  remote-endpoint = <&cros_typec_c1_ss>;
> +		};
> +	      };
> +	    };
> +	  };
> +
> +	  ports {
> +	    #address-cells = <1>;
> +	    #size-cells = <0>;
> +
> +	    port@0 {
> +	      reg = <0>;
> +	      #address-cells = <1>;
> +	      #size-cells = <0>;
> +
> +	      cros_typec_c0_ss: endpoint@0 {
> +		reg = <0>;
> +		remote-endpoint = <&usb_c0_ss>;
> +		data-lanes = <0 1 2 3>;
> +	      };
> +
> +	      cros_typec_c1_ss: endpoint@1 {
> +		reg = <1>;
> +		remote-endpoint = <&usb_c1_ss>;
> +		data-lanes = <2 3 0 1>;
> +	      };
> +	    };
> +
> +	    port@1 {
> +	      reg = <1>;
> +	      #address-cells = <1>;
> +	      #size-cells = <0>;
> +
> +	      usb_in_0: endpoint@0 {
> +		reg = <0>;
> +		remote-endpoint = <&usb_ss_0_out>;
> +	      };
> +
> +	      usb_in_1: endpoint@1 {
> +		reg = <1>;
> +		remote-endpoint = <&usb_ss_1_out>;
> +	      };
> +	    };
> +
> +	    port@2 {
> +	      reg = <2>;
> +	      dp_in: endpoint {
> +		remote-endpoint = <&dp_phy>;
> +		data-lanes = <0 1>;
> +	      };
> +	    };
>	    };
>	  };
>	};
> -- 
> https://chromeos.dev
>
Dmitry Baryshkov Oct. 25, 2024, 10:49 a.m. UTC | #3
On Tue, Oct 22, 2024 at 06:15:47PM -0700, Stephen Boyd wrote:
> Quoting Dmitry Baryshkov (2024-09-20 02:38:53)
> > On Sat, Aug 31, 2024 at 09:06:53PM GMT, Stephen Boyd wrote:

> 
> Either way the problem seems to be that I need to associate one
> drm_bridge with two displayport altmode drivers and pass some fwnode
> handle to drm_connector_oob_hotplug_event() in a way that we can map
> that back to the right output endpoint in the DP bridge graph. That
> seems to imply that we need to pass the fwnode for the usb-c-connector
> in addition to the fwnode for the drm_bridge, so that the drm_bridge
> code can look at its DT graph and find the remote node connected.
> Basically something like this:
> 
>   void drm_connector_oob_hotplug_event(struct fwnode_handle *connector_fwnode,
>                                        struct fwnode_handle
> *usb_connector_fwnode,
>                                        enum drm_connector_status status)
> 
> (We might as well also pass the number of lanes here)

I think this is a bit of an overkill.

The drm_connector_oob_hotplug_event() is fine as it is, it gets
"fwnode_handle to report the event on".

What needs to be changed (in my humble opinion) is the
drm_connector_find_by_fwnode() function (or likely a new function is to
be added): if it can not find drm_connector for the passed fwnode, it
should look it up on the parent, then on parent's parent, etc, until we
actually find the drm_connector (good) or we reach the root (sad).

And finally after getting the drm_connector, the oob_hotplug_event()
callback should also receive the fwnode argument. This way the connector
(or the bridge) can identify the fwnode (aka usb-c-connector in our
case) that caused the event.

WDYT?

> Corsola could work with this design, but we'll need to teach
> dp_altmode_probe() to look for the drm_bridge elsewhere besides as the
> parent of the usb-c-connector node. That implies using the 'displayport'
> property in the cros-ec-typec node or teaching dp_altmode_probe() to
> look for the port@1/endpoint@1 remote-endpoint handle in the
> usb-c-connector graph.
> 
> Assuming the bindings you've presented here are fine and good and I got
> over the differences between Trogdor and Corsola, then I can make mostly
> everything work with the drm_connector_oob_hotplug_event() signature
> change from above and some tweaks to dp_altmode_probe() to look for
> port@1/endpoint@1 first because that's the "logical" DP input endpoint
> in the usb-c-connector binding's graph. Great! The final roadblock I'm
> at is that HPD doesn't work on Trogdor, so I can't signal HPD through
> the typec framework.

Hmm, I thought that a normal DP's HPD GPIO works on the trogdor. Was I
misunderstanding it? But then we don't know, which USB-C connector
triggered the HPD...

> This series fixes that problem by "capturing" HPD state from the
> upstream drm_bridge, e.g. msm_dp, by hooking the struct
> drm_bridge_funcs::hpd_notify() path and injecting HPD into the typec
> messages received from the EC. That's a workaround to make the typec
> framework see HPD state changes that are otherwise invisible to the
> kernel. Newer firmwares actually tell us the state of HPD properly, but
> even then we have to read a gpio mux controlled by the EC to figure out
> which usb-c-connector is actually muxing DP when HPD changes on either
> typec_port. Having a drm_bridge in cros-ec-typec helped here because we
> could hook this path and signal HPD if we knew the firmware was fixed.
> If we don't have the drm_bridge anymore, I'm lost how to do this.

It's probably okay to add one, but let me think if we can work without
it. Can we make EC driver listen for that single HPD GPIO (by making it
an actual GPIO rather than "dp_hot") and then react to it?

> 
> Maybe the right answer here is to introduce a drm_connector_dp_typec
> structure that is created by the TCPM (cros-ec-typec) that sets a new
> DRM_BRIDGE_OP_DP_TYPEC bridge op flag? And then teach
> drm_bridge_connector about this new flag, similar to the HDMI one. The
> drm_bridge could implement some function that maps the typec_port
> (usb-c-connector) to the upstream drm_bridge (ANX7625) graph port,
> possibly all in drm_bridge_connector_oob_hotplug_event() so that nothing
> else really changes. It could also let us keep hooking the hpd_notify()
> path for the workaround needed on Trogdor. And finally it may let us
> harmonize the two DT bindings so that we only have one port@1/endpoint
> node in the usb-c-connector.

I think we have lightly discussed adding drm_connector_displayport, so
that part is okay. But my gut feeling is that there should be no _typec
part in thart picture. The DRM framework shouldn't need to know all the
Type-C details.

> 
> 
> >                 };
> >         };
> >
> >         connector@1 {
> >                 port@1 {
> >                         endpoint@0 {
> >                                 remtoe = <&usb_hub_1>;
> >                         };
> >
> >                         endpoint@1 {
> >                                 remote = <&dp_bridge_out_1>;
> >                         };
> >                 };
> >         };
> > };
> >
> > dp_bridge {
> >         ports {
> >                 port@1 {
> >                         dp_bridge_out_0: endpoint@0 {
> >                                 remote = <usb_c0_ss_dp>;
> >                                 data-lanes = <0 1>;
> >                         };
> >
> >                         dp_bridge_out_1: endpoint@1 {
> >                                 remote = <usb_c1_ss_dp>;
> >                                 data-lanes = <2 3>;
> >                         };
> >                 };
> >         };
> > };
> >
> > -------
> >
> > This one is really tough example, we didn't reach a conclusion here.
> > If the EC doesn't handle lane remapping, dp_bridge has to get
> > orientation-switch and mode-switch properties (as in the end it is the
> > dp_bridge that handles reshuffling of the lanes for the Type-C). Per the
> > DisplayPort standard the lanes are fixed (e.g. DPCD 101h explicitly
> > names lane 0, lanes 0-1, lanes 0-1-2-3).
> 
> Are those logical or physical lanes?

Physical lanes as far as I understand.

> 
> I think we'll punt on this one anyway though. We don't have any plans to
> do this orientation control mechanism so far. Previous attempts failed
> and we put an extra orientation switch control on the board to do the
> orientation flipping.

Okay, it's definitely easier this way.
Stephen Boyd Oct. 29, 2024, 8:15 p.m. UTC | #4
Quoting Dmitry Baryshkov (2024-10-25 03:49:36)
> On Tue, Oct 22, 2024 at 06:15:47PM -0700, Stephen Boyd wrote:
> > Quoting Dmitry Baryshkov (2024-09-20 02:38:53)
> > > On Sat, Aug 31, 2024 at 09:06:53PM GMT, Stephen Boyd wrote:
>
> >
> > Either way the problem seems to be that I need to associate one
> > drm_bridge with two displayport altmode drivers and pass some fwnode
> > handle to drm_connector_oob_hotplug_event() in a way that we can map
> > that back to the right output endpoint in the DP bridge graph. That
> > seems to imply that we need to pass the fwnode for the usb-c-connector
> > in addition to the fwnode for the drm_bridge, so that the drm_bridge
> > code can look at its DT graph and find the remote node connected.
> > Basically something like this:
> >
> >   void drm_connector_oob_hotplug_event(struct fwnode_handle *connector_fwnode,
> >                                        struct fwnode_handle
> > *usb_connector_fwnode,
> >                                        enum drm_connector_status status)
> >
> > (We might as well also pass the number of lanes here)
>
> I think this is a bit of an overkill.
>
> The drm_connector_oob_hotplug_event() is fine as it is, it gets
> "fwnode_handle to report the event on".

Ok. I understand that drm_*() shouldn't know about USB or type-c in
general.

>
> What needs to be changed (in my humble opinion) is the
> drm_connector_find_by_fwnode() function (or likely a new function is to
> be added): if it can not find drm_connector for the passed fwnode, it
> should look it up on the parent, then on parent's parent, etc, until we
> actually find the drm_connector (good) or we reach the root (sad).
>
> And finally after getting the drm_connector, the oob_hotplug_event()
> callback should also receive the fwnode argument. This way the connector
> (or the bridge) can identify the fwnode (aka usb-c-connector in our
> case) that caused the event.
>
> WDYT?

Ok I think I'm following along. The dp->connector_fwnode in
displayport.c will always be the usb-c-connector node in your example?
And that will search for the connector or bridge associated with that
usb-c-connector node. Then when it comes time to call
drm_connector_oob_hotplug_event() it will take the usb-c-connector
fwnode as 'connector_fwnode' and in that function we'll make
drm_connector_find_by_fwnode() implement the parent walk? The
cros-ec-typec compatible node will register a drm_bridge in all cases,
and that is the parent of the usb-c-connector node, so the walk will end
there.

Then you want to pass the usb-c-connector fwnode to
connector->funcs->oob_hotplug_event()? So
drm_bridge_connector_oob_hotplug_event() changes to also get the
usb-c-connector fwnode. This plan should work.

At this point we need to tell the DP bridge, like IT6505, that it's one
or the other output endpoints that it should use, but we haven't
directly connected the usb-c-connector to the output ports of IT6505
because drm_of_find_panel_or_bridge() can't find the parent of the
usb-c-connector if we connect the DP bridge to the usb-c-connector
graphs. We'll need a way for the bridge to know which output port is
connected to a usb-c-connector fwnode. Some sort of API like

 fwnode_graph_get_endpoint_connected_to_fwnode(bridge_fwnode, usb_c_fwnode)

that takes the bridge fwnode and traverses the graph to find the
endpoint in that's connected to 'usb_c_fwnode'. That traversal API will
need help from the intermediate node, cros-ec-typec, so maybe it is
better as a drm_bridge API that uses some new drm_bridge_funcs callback.
This way IT6505 can ask the bridge chain which output DP endpoint is
actually associated with the connector fwnode it gets from the
oob_hotplug_event() callback.

Here's the two DT snippets that I've ended up with:

typec {
        compatible = "google,cros-ec-typec";

        ports {
                port@0 {
                        reg = <0>;
                        typec_dp_in: endpoint {
                                 remote-endpoint = <&usb_1_qmp_phy_out_dp>;
                        };
                };

                port@1 {
                        reg = <1>;
                        typec_usb0_in: endpoint@0 {
                                 reg = <0>;
                                 remote-endpoint = <&usb_hub_dfp1_ss>;
                        };
                        typec_usb1_in: endpoint@1 {
                                 reg = <1>;
                                 remote-endpoint = <&usb_hub_dfp2_ss>;
                        };
                }

                // This port is not really needed because we know the
		// mapping from input ports to usb-c-connectors
                port@2 {
                        reg = <2>;
                        typec0_out: endpoint@0 {
                                 reg = <0>;
                                 remote-endpoint = <&usb_c0_ss_in>;
                        };
                        typec1_out: endpoint@1 {
                                 reg = <1>;
                                 remote-endpoint = <&usb_c1_ss_in>;
                        };
                }
        };

        usb_c0: connector@0 {
                compatible = "usb-c-connector";
                reg = <0>;

                ports {
                        port@0 {
                                reg = <0>;
                                usb_c0_hs_in: endpoint {
                                        remote-endpoint = <&usb_hub_dfp1_hs>;
                                };
                        };

                        port@1 {
                                reg = <1>;
                                usb_c0_ss_in: endpoint {
                                        remote-endpoint = <&typec0_out>;
                                };
                        };
                };
        };

        usb_c1: connector@1 {
                compatible = "usb-c-connector";
                reg = <1>;

                ports {
                        port@0 {
                                reg = <0>;
                                usb_c1_hs_in: endpoint {
                                        remote-endpoint = <&usb_hub_dfp2_hs>;
                                };
                        };

                        port@1 {
                                reg = <1>;
                                usb_c1_ss_in: endpoint {
                                        remote-endpoint = <&typec1_out>;
                                };
                        };
                };
        };
};

&usb_1_qmpphy {
        ports {
                port@0 {
                        endpoint@0 {
                                data-lanes = <0 1>;
                                // this might go to USB-3 hub
                        };

                        usb_1_qmp_phy_out_dp: endpoint@1 {
                                remote-endpoint = <&typec_dp_in>;
                                data-lanes = <2 3>;
                        };
                }
        };
};

-------

typec {
        ports {
                port@0 {
                        reg = <0>;
                        typec_dp0_in: endpoint@0 {
                                 reg = <0>;
                                 remote-endpoint = <&dp_bridge_out_0>;
                        };
                        typec_dp1_in: endpoint@1 {
                                 reg = <1>;
                                 remote-endpoint = <&dp_bridge_out_1>;
                        };
                };

                port@1 {
                        reg = <1>;
                        typec_usb0_in: endpoint@0 {
                                 reg = <0>;
                                 remote-endpoint = <&usb_hub_0_ss>;
                        };
                        typec_usb1_in: endpoint@1 {
                                 reg = <1>;
                                 remote-endpoint = <&usb_hub_1_ss>;
                        };
                }
        };

        connector@0 {
                port@1 {
                        endpoint@0 {
                                remote-endpoint = <&usb_hub_0_hs>;
                        };
                };
        };

        connector@1 {
                port@1 {
                        endpoint@0 {
                                remote-endpoint = <&usb_hub_1_hs>;
                        };
                };
        };
};

dp_bridge {
        ports {
                port@1 {
                        dp_bridge_out_0: endpoint@0 {
                                remote-endpoint = <&typec_dp0_in>;
                                data-lanes = <0 1>;
                        };

                        dp_bridge_out_1: endpoint@1 {
                                remote-endpoint = <&typec_dp1_in>;
                                data-lanes = <2 3>;
                        };
                };
        };
};

-------

I wonder about a case where we may take two lanes and connect them to a
usb-c-connector and then take the other two lanes and send them through
a mux to two more usb-c-connectors. I think we'll need another property
in that case that indicates which input DP endpoints correspond to the
usb-c-connector nodes.

typec {
        ports {
                port@0 {
                        reg = <0>;
                        typec_dp0_in: endpoint@0 {
                                 reg = <0>;
                                 remote-endpoint = <&dp_bridge_out_0>;
                        };
                        typec_dp1_in: endpoint@1 {
                                 reg = <1>;
                                 remote-endpoint = <&dp_bridge_out_1>;
                        };
                };

                port@1 {
                        reg = <1>;
                        typec_usb0_in: endpoint@0 {
                                 reg = <0>;
                                 remote-endpoint = <&usb_hub_0_ss>;
                        };
                        typec_usb1_in: endpoint@1 {
                                 reg = <1>;
                                 remote-endpoint = <&usb_hub_1_ss>;
                        };
                        typec_usb2_in: endpoint@2 {
                                 reg = <2>;
                                 remote-endpoint = <&usb_hub_2_ss>;
                        };
                }
        };

	dp-2-usb-mapping = <0 0>, <1 1>, <1 2>;
};

This property would indicate dp endpoint 0 goes to usb-c-connector 0
while dp endpoint 1 goes to usb-c-connector 1 and 2. I don't have this
hardware but I could see how someone might do this by adding another mux
that the EC controls. I don't want to design a binding and have to
rework it in the future to handle this new case. I hope adding a new
property, or getting more information from the EC firmware, will be
sufficient to describe the linkage between the DP endpoint and the
connectors managed by the cros-ec-typec device.

>
> > Corsola could work with this design, but we'll need to teach
> > dp_altmode_probe() to look for the drm_bridge elsewhere besides as the
> > parent of the usb-c-connector node. That implies using the 'displayport'
> > property in the cros-ec-typec node or teaching dp_altmode_probe() to
> > look for the port@1/endpoint@1 remote-endpoint handle in the
> > usb-c-connector graph.
> >
> > Assuming the bindings you've presented here are fine and good and I got
> > over the differences between Trogdor and Corsola, then I can make mostly
> > everything work with the drm_connector_oob_hotplug_event() signature
> > change from above and some tweaks to dp_altmode_probe() to look for
> > port@1/endpoint@1 first because that's the "logical" DP input endpoint
> > in the usb-c-connector binding's graph. Great! The final roadblock I'm
> > at is that HPD doesn't work on Trogdor, so I can't signal HPD through
> > the typec framework.
>
> Hmm, I thought that a normal DP's HPD GPIO works on the trogdor. Was I
> misunderstanding it? But then we don't know, which USB-C connector
> triggered the HPD...

By HPD not working on Trogdor I mean that the EC doesn't tell the kernel
about the state of HPD for a usb-c-connector in software. Instead, HPD
is signaled directly to the DP controller in hardware via a GPIO. It is
as you suspect, we don't know which USB-C connector has HPD unless we
read the mux controlled by the EC and combine that with what the DP
driver knows about the state of the HPD pin.

>
> > This series fixes that problem by "capturing" HPD state from the
> > upstream drm_bridge, e.g. msm_dp, by hooking the struct
> > drm_bridge_funcs::hpd_notify() path and injecting HPD into the typec
> > messages received from the EC. That's a workaround to make the typec
> > framework see HPD state changes that are otherwise invisible to the
> > kernel. Newer firmwares actually tell us the state of HPD properly, but
> > even then we have to read a gpio mux controlled by the EC to figure out
> > which usb-c-connector is actually muxing DP when HPD changes on either
> > typec_port. Having a drm_bridge in cros-ec-typec helped here because we
> > could hook this path and signal HPD if we knew the firmware was fixed.
> > If we don't have the drm_bridge anymore, I'm lost how to do this.
>
> It's probably okay to add one, but let me think if we can work without
> it. Can we make EC driver listen for that single HPD GPIO (by making it
> an actual GPIO rather than "dp_hot") and then react to it?

I don't know how we handle the attention message, HPD_IRQ, because
that's a short pulse that the kernel may miss when this is a GPIO that
has to be triggered when both falling and rising. When the pin goes
directly to the DP controller this is fine because the hardware can
detect that. Similarly, when the EC sends the message about an HPD_IRQ
we can replay that into the type-c framework and signal attention
through drm_connector_oob_hotplug_event()/hpd_notify() paths.

>
> >
> > Maybe the right answer here is to introduce a drm_connector_dp_typec
> > structure that is created by the TCPM (cros-ec-typec) that sets a new
> > DRM_BRIDGE_OP_DP_TYPEC bridge op flag? And then teach
> > drm_bridge_connector about this new flag, similar to the HDMI one. The
> > drm_bridge could implement some function that maps the typec_port
> > (usb-c-connector) to the upstream drm_bridge (ANX7625) graph port,
> > possibly all in drm_bridge_connector_oob_hotplug_event() so that nothing
> > else really changes. It could also let us keep hooking the hpd_notify()
> > path for the workaround needed on Trogdor. And finally it may let us
> > harmonize the two DT bindings so that we only have one port@1/endpoint
> > node in the usb-c-connector.
>
> I think we have lightly discussed adding drm_connector_displayport, so
> that part is okay. But my gut feeling is that there should be no _typec
> part in thart picture. The DRM framework shouldn't need to know all the
> Type-C details.
>

Alright, got it.
Stephen Boyd Oct. 31, 2024, 9:45 p.m. UTC | #5
Quoting Dmitry Baryshkov (2024-10-31 11:42:36)
> On Tue, Oct 29, 2024 at 01:15:51PM -0700, Stephen Boyd wrote:
> > At this point we need to tell the DP bridge, like IT6505, that it's one
> > or the other output endpoints that it should use, but we haven't
> > directly connected the usb-c-connector to the output ports of IT6505
> > because drm_of_find_panel_or_bridge() can't find the parent of the
> > usb-c-connector if we connect the DP bridge to the usb-c-connector
> > graphs. We'll need a way for the bridge to know which output port is
> > connected to a usb-c-connector fwnode. Some sort of API like
>
> I think that the final bridge should be the IT6505. It can save you from
> some troubles, like the inter-bridge lane negotiation. Please remember
> that using lanes 2-3 as primary lanes doesn't seem to fall into the
> standard DisplayPort usage. It is documented by USB-C and only because
> of the orientation switching.

If the final bridge is IT6505 then drm_of_find_panel_or_bridge() isn't
called and I think we're OK. But then we have to traverse the
remote-endpoint of the usb-c-connector to IT6505 in displayport.c in the
Corsola case while knowing to look at the parent of the usb-c-connector
node and traversing the remote-endpoint to the QMP phy in the Trogdor
case. The logic in dp_altmode_probe() is like

  if (port@1/endpoint@1 exists in usb-c-connector)
    connector_fwnode = port@1/endpoint@1/remote-endpoint
  else if (cros-ec-typec/port exists)
    connector_fwnode = cros-ec-typec/port@0/endpoint/remote-endpoint
  else
    original stuff

If we have the crazy three usb-c-connector design it can still work
because we'd have something like

  cros-ec-typec {
    port {
      dp_endpoint: endpoint {
        remote-endpoint = <&dp_ml0_ml1>;
      };
    };

    usb-c-connector@0 {
      port@1 {
        endpoint {
          remote-endpoint = <&hub_ss0>;
       };
       // Implicitly dp_ml0_ml1
      };
    };
    usb-c-connector@1 {
      port@1 {
        endpoint@0 {
          remote-endpoint = <&hub_ss1>;
        };
        endpoint@1 {
          remote-endpoint = <&dp_ml2_ml3>;
        };
      };
    };
    usb-c-connector@2 {
      port@1 {
        endpoint {
          remote-endpoint = <&hub_ss2>;
        };
       // Implicitly dp_ml0_ml1
      };
    };
  };

(I like thinking about this 3 connector case because it combines both
Trogdor and Corsola designs so I can talk about both cases at the same
time)

I don't know what happens when we have 4 connectors though, with 2 going
to one pair of lanes and 2 going to the other 2 lanes. Maybe it's better
to always have a DP input port in cros-ec-typec to avoid this problem
and map back to the endpoint explicitly.

  cros-ec-typec {
    port {
      dp_endpoint0: endpoint@0 {
        remote-endpoint = <&dp_ml0_ml1>;
      };
      dp_endpoint1: endpoint@1 {
        remote-endpoint = <&dp_ml2_ml3>;
      };
    };

    usb-c-connector@0 {
      port@1 {
        endpoint@0 {
          remote-endpoint = <&hub_ss0>;
       };
       endpoint@1 {
         remote-endpoint = <&dp_endpoint0>;
       };
      };
    };
    usb-c-connector@1 {
      port@1 {
        endpoint@0 {
          remote-endpoint = <&hub_ss1>;
        };
        endpoint@1 {
          remote-endpoint = <&dp_endpoint1>;
        };
      };
    };
    usb-c-connector@2 {
      port@1 {
        endpoint@0 {
          remote-endpoint = <&hub_ss2>;
        };
        endpoint@1 {
          remote-endpoint = <&dp_endpoint1>;
        };
      };
    };
  };

Or use a displayport property that goes to connector node itself so that
we don't extend the graph binding of the usb-c-connector.

  cros-ec-typec {
    usb-c-connector@0 {
      altmodes {
        displayport {
          connector = <&dp_ml0_ml1>;
        };
      };
      port@1 {
        endpoint@0 {
          remote-endpoint = <&hub_ss0>;
       };
      };
    };
    usb-c-connector@1 {
      altmodes {
        displayport {
          connector = <&dp_ml2_ml3>;
        };
      };
      port@1 {
        endpoint {
          remote-endpoint = <&hub_ss1>;
        };
      };
    };
    usb-c-connector@2 {
      altmodes {
        displayport {
          connector = <&dp_ml2_ml3>;
        };
      };
      port@1 {
        endpoint {
          remote-endpoint = <&hub_ss2>;
        };
      };
    };
  };

  it6505 {
    ports {
      port@1 {
        dp_ml0_ml1: endpoint@0 {
          remote-endpoint = <??>;
        };
        dp_ml2_ml3: endpoint@1 {
          remote-endpoint = <??>;
        };
      };
    };
  };

The logic could look at a node like usb-c-connector@2, find
altmodes/display node, and look for a 'connector' property that points
at the endpoint of the last bridge. If we don't use the OF graph binding
it makes it easier to point at the same endpoint in the QMP phy or the
IT6505 graph from more than one usb-c-connector. This also makes it very
clear that we intend to pass that fwnode as the 'connector_fwnode' to
oob_hotplug_event().

If we want to actually populate the 'remote-endpoint' property of IT6505
we will need to make a graph in cros-ec-typec.

  cros-ec-typec {
    port {
      dp_endpoint0: endpoint@0 {
        remote-endpoint = <&dp_ml0_ml1>;
      };
      dp_endpoint1: endpoint@1 {
        remote-endpoint = <&dp_ml2_ml3>;
      };
    };
    usb-c-connector@0 {
      altmodes {
        displayport {
          connector = <&dp_endpoint0>;
        };
      };
      port@1 {
        endpoint@0 {
          remote-endpoint = <&hub_ss0>;
       };
      };
    };
    usb-c-connector@1 {
      altmodes {
        displayport {
          connector = <&dp_endpoint1>;
        };
      };
      port@1 {
        endpoint {
          remote-endpoint = <&hub_ss1>;
        };
      };
    };
    usb-c-connector@2 {
      altmodes {
        displayport {
          connector = <&dp_endpoint1>;
        };
      };
      port@1 {
        endpoint {
          remote-endpoint = <&hub_ss2>;
        };
      };
    };
  };

  it6505 {
    ports {
      port@1 {
        dp_ml0_ml1: endpoint@0 {
          remote-endpoint = <dp_endpoint0>;
        };
        dp_ml2_ml3: endpoint@1 {
          remote-endpoint = <dp_endpoint1>;
        };
      };
    };
  };

and then the logic in displayport.c will have to check if the
'connector' property points at a graph endpoint, traverse that to the
remote-endpoint, and consider that the connector_fwnode.

>
> Maybe that's just it? Register DP_bridge (or QMP PHY) as
> orientation-switch? Then you don't need any extra API for the lane
> mapping? The cross-ec-typec can provide orientation information and the
> USB-C-aware controller will follow the lane mapping.

I'm not really following but I don't think the DT binding discussed here
prevents that.

>
> >
> >  fwnode_graph_get_endpoint_connected_to_fwnode(bridge_fwnode, usb_c_fwnode)
> >
> > that takes the bridge fwnode and traverses the graph to find the
> > endpoint in that's connected to 'usb_c_fwnode'. That traversal API will
> > need help from the intermediate node, cros-ec-typec, so maybe it is
> > better as a drm_bridge API that uses some new drm_bridge_funcs callback.
> > This way IT6505 can ask the bridge chain which output DP endpoint is
> > actually associated with the connector fwnode it gets from the
> > oob_hotplug_event() callback.
> >
> > Here's the two DT snippets that I've ended up with:
> >
> > typec {
> >         compatible = "google,cros-ec-typec";
> >
> >         ports {
> >                 port@0 {
> >                         reg = <0>;
> >                         typec_dp_in: endpoint {
> >                                  remote-endpoint = <&usb_1_qmp_phy_out_dp>;
> >                         };
> >                 };
> >
> >                 port@1 {
> >                         reg = <1>;
> >                         typec_usb0_in: endpoint@0 {
> >                                  reg = <0>;
> >                                  remote-endpoint = <&usb_hub_dfp1_ss>;
> >                         };
> >                         typec_usb1_in: endpoint@1 {
> >                                  reg = <1>;
> >                                  remote-endpoint = <&usb_hub_dfp2_ss>;
> >                         };
> >                 }
> >
> >                 // This port is not really needed because we know the
> >               // mapping from input ports to usb-c-connectors
> >                 port@2 {
> >                         reg = <2>;
> >                         typec0_out: endpoint@0 {
> >                                  reg = <0>;
> >                                  remote-endpoint = <&usb_c0_ss_in>;
> >                         };
> >                         typec1_out: endpoint@1 {
> >                                  reg = <1>;
> >                                  remote-endpoint = <&usb_c1_ss_in>;
> >                         };
> >                 }
>
> Why do we need these two ports? Can't &usb_hub_dfpN_ss be connected
> directly to the usb_cN_ss_in? I understand that you probably want to
> express the internal structure of the lane switching, but I think that's
> a bit of the overkill. Leaving this to the other commenters / DT
> maintainers.

We don't need port@2 because we know that DP goes there.

>
> >         };
> >
> >         usb_c0: connector@0 {
> >                 compatible = "usb-c-connector";
> >                 reg = <0>;
> >
> >                 ports {
> >                         port@0 {
> >                                 reg = <0>;
> >                                 usb_c0_hs_in: endpoint {
> >                                         remote-endpoint = <&usb_hub_dfp1_hs>;
> >                                 };
> >                         };
> >
> >                         port@1 {
> >                                 reg = <1>;
> >                                 usb_c0_ss_in: endpoint {
> >                                         remote-endpoint = <&typec0_out>;
> >                                 };
> >                         };
> >                 };
> >         };
> >
> >         usb_c1: connector@1 {
> >                 compatible = "usb-c-connector";
> >                 reg = <1>;
> >
> >                 ports {
> >                         port@0 {
> >                                 reg = <0>;
> >                                 usb_c1_hs_in: endpoint {
> >                                         remote-endpoint = <&usb_hub_dfp2_hs>;
> >                                 };
> >                         };
> >
> >                         port@1 {
> >                                 reg = <1>;
> >                                 usb_c1_ss_in: endpoint {
> >                                         remote-endpoint = <&typec1_out>;
> >                                 };
> >                         };
> >                 };
> >         };
> > };
> >
> > &usb_1_qmpphy {
> >         ports {
> >                 port@0 {
> >                         endpoint@0 {
> >                                 data-lanes = <0 1>;
> >                                 // this might go to USB-3 hub
> >                         };
> >
> >                         usb_1_qmp_phy_out_dp: endpoint@1 {
> >                                 remote-endpoint = <&typec_dp_in>;
> >                                 data-lanes = <2 3>;
> >                         };
> >                 }
> >         };
> > };
> >
> > -------
> >
> > typec {
> >         ports {
> >                 port@0 {
> >                         reg = <0>;
> >                         typec_dp0_in: endpoint@0 {
> >                                  reg = <0>;
> >                                  remote-endpoint = <&dp_bridge_out_0>;
> >                         };
> >                         typec_dp1_in: endpoint@1 {
> >                                  reg = <1>;
> >                                  remote-endpoint = <&dp_bridge_out_1>;
> >                         };
> >                 };
> >
> >                 port@1 {
> >                         reg = <1>;
> >                         typec_usb0_in: endpoint@0 {
> >                                  reg = <0>;
> >                                  remote-endpoint = <&usb_hub_0_ss>;
> >                         };
> >                         typec_usb1_in: endpoint@1 {
> >                                  reg = <1>;
> >                                  remote-endpoint = <&usb_hub_1_ss>;
> >                         };
> >                 }
> >         };
> >
> >         connector@0 {
> >                 port@1 {
> >                         endpoint@0 {
> >                                 remote-endpoint = <&usb_hub_0_hs>;
>
> port@1 is for SS lanes, so something is wrong here.

I meant port@0

>
> >                         };
> >                 };
> >         };
> >
> >         connector@1 {
> >                 port@1 {
> >                         endpoint@0 {
> >                                 remote-endpoint = <&usb_hub_1_hs>;
> >                         };
> >                 };
> >         };
> > };
> >
> > dp_bridge {
> >         ports {
> >                 port@1 {
> >                         dp_bridge_out_0: endpoint@0 {
> >                                 remote-endpoint = <&typec_dp0_in>;
> >                                 data-lanes = <0 1>;
> >                         };
> >
> >                         dp_bridge_out_1: endpoint@1 {
> >                                 remote-endpoint = <&typec_dp1_in>;
> >                                 data-lanes = <2 3>;
> >                         };
> >                 };
> >         };
> > };
> >
> > -------
> >
> > I wonder about a case where we may take two lanes and connect them to a
> > usb-c-connector and then take the other two lanes and send them through
> > a mux to two more usb-c-connectors. I think we'll need another property
> > in that case that indicates which input DP endpoints correspond to the
> > usb-c-connector nodes.
> >
> > typec {
> >         ports {
> >                 port@0 {
> >                         reg = <0>;
> >                         typec_dp0_in: endpoint@0 {
> >                                  reg = <0>;
> >                                  remote-endpoint = <&dp_bridge_out_0>;
> >                         };
> >                         typec_dp1_in: endpoint@1 {
> >                                  reg = <1>;
> >                                  remote-endpoint = <&dp_bridge_out_1>;
> >                         };
> >                 };
> >
> >                 port@1 {
> >                         reg = <1>;
> >                         typec_usb0_in: endpoint@0 {
> >                                  reg = <0>;
> >                                  remote-endpoint = <&usb_hub_0_ss>;
> >                         };
> >                         typec_usb1_in: endpoint@1 {
> >                                  reg = <1>;
> >                                  remote-endpoint = <&usb_hub_1_ss>;
> >                         };
> >                         typec_usb2_in: endpoint@2 {
> >                                  reg = <2>;
> >                                  remote-endpoint = <&usb_hub_2_ss>;
> >                         };
> >                 }
> >         };
> >
> >       dp-2-usb-mapping = <0 0>, <1 1>, <1 2>;
>
> dp-to-typec-mapping?

Sure

>
> > };
> >
> > This property would indicate dp endpoint 0 goes to usb-c-connector 0
> > while dp endpoint 1 goes to usb-c-connector 1 and 2. I don't have this
> > hardware but I could see how someone might do this by adding another mux
> > that the EC controls. I don't want to design a binding and have to
> > rework it in the future to handle this new case. I hope adding a new
> > property, or getting more information from the EC firmware, will be
> > sufficient to describe the linkage between the DP endpoint and the
> > connectors managed by the cros-ec-typec device.
>
> Does it change anything from the DP point of view? It is still either
> lanes 0-1 or lanes 2-3? I'd really like to inject the hotplug OOB event
> to the dp_bridge letting it get one of the endpoints as a HPD even
> source.

Nothing changes from the DP point of view. I understand that you want
the bridge to see one of its endpoints as the 'connector_fwnode' passed
to oob_hotplug_event().

>
> > > > Corsola could work with this design, but we'll need to teach
> > > > dp_altmode_probe() to look for the drm_bridge elsewhere besides as the
> > > > parent of the usb-c-connector node. That implies using the 'displayport'
> > > > property in the cros-ec-typec node or teaching dp_altmode_probe() to
> > > > look for the port@1/endpoint@1 remote-endpoint handle in the
> > > > usb-c-connector graph.
> > > >
> > > > Assuming the bindings you've presented here are fine and good and I got
> > > > over the differences between Trogdor and Corsola, then I can make mostly
> > > > everything work with the drm_connector_oob_hotplug_event() signature
> > > > change from above and some tweaks to dp_altmode_probe() to look for
> > > > port@1/endpoint@1 first because that's the "logical" DP input endpoint
> > > > in the usb-c-connector binding's graph. Great! The final roadblock I'm
> > > > at is that HPD doesn't work on Trogdor, so I can't signal HPD through
> > > > the typec framework.
> > >
> > > Hmm, I thought that a normal DP's HPD GPIO works on the trogdor. Was I
> > > misunderstanding it? But then we don't know, which USB-C connector
> > > triggered the HPD...
> >
> > By HPD not working on Trogdor I mean that the EC doesn't tell the kernel
> > about the state of HPD for a usb-c-connector in software. Instead, HPD
> > is signaled directly to the DP controller in hardware via a GPIO. It is
> > as you suspect, we don't know which USB-C connector has HPD unless we
> > read the mux controlled by the EC and combine that with what the DP
> > driver knows about the state of the HPD pin.
>
> I see. So the HPD event gets delivered to the DP controller, but we
> really need some API to read the port? If it's not the
> orientation-switch, of course.

Yes. This is needed to understand what USB type-c connector the DP
signals should go to. In the case of Corsola/IT6505 it's needed to know
which two lanes should be sent if both type-c connectors/ports are
capable of DP altmode. On Corsola, the EC could tell the kernel that
both ports are in DP altmode but the EC is also controlling the AUX
channel mux that decides which usb-c-connector type-c port is actually
displaying DP.
Stephen Boyd Nov. 8, 2024, 12:28 a.m. UTC | #6
Quoting Dmitry Baryshkov (2024-10-31 15:54:49)
> On Thu, Oct 31, 2024 at 02:45:29PM -0700, Stephen Boyd wrote:
> > Quoting Dmitry Baryshkov (2024-10-31 11:42:36)
> > > On Tue, Oct 29, 2024 at 01:15:51PM -0700, Stephen Boyd wrote:
> >
> > Or use a displayport property that goes to connector node itself so that
> > we don't extend the graph binding of the usb-c-connector.
> >
> >   cros-ec-typec {
> >     usb-c-connector@0 {
> >       altmodes {
> >         displayport {
> >           connector = <&dp_ml0_ml1>;
>
> I think this has been frowned upon. Not exactly this, but adding the
> displayport = <&foo>.

Do you have a pointer to that discussion? I'd like to understand the
reasoning.


>
> Thus it can only go to the swnode that is generated in software by the
> cros-ec driver.

I recall swnode as a way to sidestep figuring out the DT bindings for
usb typec. Where is this swnode being made? Somewhere inside the typec
framework?

>
> >         };
> >       };
> >       port@1 {
> >         endpoint@0 {
> >           remote-endpoint = <&hub_ss0>;
> >        };
> >       };
> >     };
> >     usb-c-connector@1 {
> >       altmodes {
> >         displayport {
> >           connector = <&dp_ml2_ml3>;
> >         };
> >       };
> >       port@1 {
> >         endpoint {
[....]
> >
> > >
> > > Maybe that's just it? Register DP_bridge (or QMP PHY) as
> > > orientation-switch? Then you don't need any extra API for the lane
> > > mapping? The cross-ec-typec can provide orientation information and the
> > > USB-C-aware controller will follow the lane mapping.
> >
> > I'm not really following but I don't think the DT binding discussed here
> > prevents that.
>
> I'm thinking about:
>
> it6505 {
>   orientation-switch;
>
>   ports {
>     port@1 {
>       it6505_dp_out: remote-endpoint = <&cros_ec_dp>;
>       data-lanes = <0 1>;
>     };
>   };
> };
>
> cros-ec {
>   port {
>     cross_ec_dp: remote-endpoint = <&it6505_dp_out>;
>   };
>
>   connector@0 {
>     reg = <0>;
>     cros,dp-orientation = "normal";
>
>     ports {
>       // all USB HS and SS ports as usual;
>     };
>   };
>
>   connector@1 {
>     reg = <1>;
>     cros,dp-orientation = "reverse";
>
>     ports {
>       // all USB HS and SS ports as usual;
>     };
>   };
>
>   connector@2 {
>     reg = <2>;
>     cros,dp-orientation = "reverse";
>
>     ports {
>       // all USB HS and SS ports as usual;
>     };
>   };
>
>   connector@3 {
>     reg = <3>;
>     cros,dp-orientation = "normal";
>
>     ports {
>       // all USB HS and SS ports as usual;
>     };
>   };
> };
>
> The cros-ec registers single drm bridge which will generate HPD events
> except on Trogdor, etc. At the same time, cros-ec requests the
> typec_switch_get(). When the cros-ec detects that the connector@N it
> being used for DP, it just generates corresponding typec_switch_set()
> call, setting the orientation of the it6505 (or QMP PHY). The rest can
> be handled either by EC's HPD code or by DP's HPD handler, the
> orientation should already be a correct one.
>
> So, yes. It requires adding the typec_switch_desc implementation _in_
> the it6505 (or in any other component which handles the 0-1 or 2-3
> selection). On the other hand as I wrote previously, the 0-1 / 2-3 is
> the USB-C functionality, not the DP one.
>

I don't think we should be adding typec code to pure display hardware
drivers like IT6505. To keep the driver focused on display stuff I
proposed implementing runtime lane assignment for drm_bridge chains
because DP has lanes. My understanding is that not all display
technologies have lanes, so implementing generic lane assignment
functionality is overkill/incorrect. DP has physical lanes in hardware
though, and those physical lanes are assigned to certain pins in the
type-c DP altmode spec, so it's not overkill to think about lanes when
the bridge is a DP bridge wired up to a type-c connector.

Long story short, I don't see how we can avoid _any_ lane assignment
logic in drm_bridge. The logic shouldn't walk the entire bridge chain,
but it should at least act on the bridge that is a DP bridge. I think
you're saying pretty much the same thing here, but you want the lane
remapping to be done via the typec layer whereas I want it to be done in
the drm_bridge layer. To me it looks out of place to add a
typec_switch_desc inside each DP drm_bridge because we duplicate the
logic about USB type-c DP altmode lane assignment to each DP bridge. A
DP bridge should just think about DP and not know or care about USB
type-c.

This is what's leading me to think we need some sort of lane assignment
capability at the DP connector. How that assignment flows from the DP
connector created in drm_bridge_connector.c to the hardware is where it
is less clear to me. Should that be implemented as a typec_switch_desc,
essentially out of band with drm_bridge, or as some drm_bridge_funcs
function similar to struct drm_bridge_funcs::hdmi_*()? If you look at
IT6505 in it6505_get_extcon_property() it actually wants to pull the
orientation of the type-c port with extcon_get_property(EXTCON_DISP_DP,
EXTCON_PROP_USB_TYPEC_POLARITY). Maybe pushing the orientation to the DP
bridge is backwards and we should be exposing this as some sort of
connector API that the drm_bridge can query whenever it wants.

What about ANX7625 where two DP lanes go to a cross-point switch before
leaving the chip on one of two pairs of lanes? This hardware is a DP
bridge smashed together with an orientation switch (typec_switch_desc)
so that you can simply wire the output pins up to a USB type-c connector
and support 2 lanes DP altmode. Qualcomm's QMP phy is quite similar.
Presumably we'd want the ANX driver to implement both a drm_bridge and a
typec_switch_desc if it was directly connected to a usb-c-connector
node. It's also interesting to think of the DT binding here, likely we
would have one output port in the ANX node's graph that represents the
combined DP and USB data that's connected to the SuperSpeed endpoint in
the usb-c-connector.

In the case where two lanes are wired to one USB type-c connector and
the other two lanes are wired to a different USB type-c connector it
would be odd to keep the typec_switch_desc and figure out a way to
mangle the lanes we want for a USB type-c connector by setting the
orientation of the typec_switch_desc. The chip isn't really acting as a
typec orientation control here because it isn't combining USB data and
DP data for a single USB type-c port. In fact, the type-c port has an
orientation and we actively don't want to tell the ANX7625 driver about
that port orientation because the orientation control is implemented
between the ANX part and the type-c connector by some redriver
controlled by the EC.

To satisfy all these cases it almost feels like we need to make the DP
connector have an "orientation", per your earlier DT snippet it would be
"reversed" or "normal", even though in hardware a DP connector has no
such concept because it can only be plugged in one way. All cases look
to be covered if we say that the drm_connector can have an orientation,
"normal" or "reversed", and we allow the bridge drivers to query that
whenever they want with some bridge/connector API. The typical case will
be that the orientation is normal, but we can make
drm_connector_oob_hotplug_event() change that to "reversed" when the
port is different.

This leaves us with the binding you propose above, and then some sort of
property that indicates the orientation of the DP connector. Instead of
being vendor specific I wonder if we can simply have a property like
"dp-reverse-orientation" in the connector node that the displayport.c
driver can look for to set the connector orientation to the reverse one
when DP altmode is entered on the port.

This is what I have:

 it6505 {
   ports {
     port@1 {
       it6505_dp_out: remote-endpoint = <&cros_ec_dp>;
       data-lanes = <0 1>;
     };
   };
 };

 cros-ec {
   port {
     cross_ec_dp: remote-endpoint = <&it6505_dp_out>;
   };

   connector@0 {
     reg = <0>;

     ports {
       // all USB HS and SS ports as usual;
     };
   };

   connector@1 {
     reg = <1>;
     dp-reverse-orientation;

     ports {
       // all USB HS and SS ports as usual;
     };
   };

or ANX, swap out for it6505 node:

 anx7625 {
   ports {
     port@1 {
       anx7625_dp_out: remote-endpoint = <&cros_ec_dp>;
       data-lanes = <0 1>;
     };
   };
 };

and then a drm_bridge is created in cros-ec to terminate the bridge
chain. The displayport altmode driver will find the drm_bridge and the
drm_connector from the cros-ec node. When DP altmode is entered the
displayport altmode driver will set the drm_connector orientation based
on the presence of the dp-reverse-orientation property. We'll be able to
hook the hpd_notify() path in cros-ec by adding code to the drm_bridge
made there to do the HPD workaround. I'm not sure we need to use an
auxiliary device in this case, because it's a one-off solution for
cros-ec. And we don't even need to signal HPD from the cros-ec
drm_bridge because the oob_hotplug event will do it for us. If anything,
we need that displayport.c code to skip sending the hotplug event when
"no-hpd" is present in the cros-ec node. Note, this works for any number
of usb-c-connector nodes. And finally, DP bridges like IT6505 don't need
to implement a typec_switch_desc, they can simply support flipping the
orientation by querying the drm_connector for the bridge chain when they
see fit. ANX7625 can support that as well when it doesn't see the
'orientation-switch' property.

Did I miss anything? I suspect a drm_connector having an orientation is
the most controversial part of this proposal.
Dmitry Baryshkov Nov. 9, 2024, 7:05 a.m. UTC | #7
On Thu, Nov 07, 2024 at 04:28:24PM -0800, Stephen Boyd wrote:
> Quoting Dmitry Baryshkov (2024-10-31 15:54:49)
> > On Thu, Oct 31, 2024 at 02:45:29PM -0700, Stephen Boyd wrote:
> > > Quoting Dmitry Baryshkov (2024-10-31 11:42:36)
> > > > On Tue, Oct 29, 2024 at 01:15:51PM -0700, Stephen Boyd wrote:
> > >
> > > Or use a displayport property that goes to connector node itself so that
> > > we don't extend the graph binding of the usb-c-connector.
> > >
> > >   cros-ec-typec {
> > >     usb-c-connector@0 {
> > >       altmodes {
> > >         displayport {
> > >           connector = <&dp_ml0_ml1>;
> >
> > I think this has been frowned upon. Not exactly this, but adding the
> > displayport = <&foo>.
> 
> Do you have a pointer to that discussion? I'd like to understand the
> reasoning.

No, unfortunately I couldn't find it.

> 
> 
> >
> > Thus it can only go to the swnode that is generated in software by the
> > cros-ec driver.
> 
> I recall swnode as a way to sidestep figuring out the DT bindings for
> usb typec. Where is this swnode being made? Somewhere inside the typec
> framework?

In the cros-ec driver?

> 
> >
> > >         };
> > >       };
> > >       port@1 {
> > >         endpoint@0 {
> > >           remote-endpoint = <&hub_ss0>;
> > >        };
> > >       };
> > >     };
> > >     usb-c-connector@1 {
> > >       altmodes {
> > >         displayport {
> > >           connector = <&dp_ml2_ml3>;
> > >         };
> > >       };
> > >       port@1 {
> > >         endpoint {
> [....]
> > >
> > > >
> > > > Maybe that's just it? Register DP_bridge (or QMP PHY) as
> > > > orientation-switch? Then you don't need any extra API for the lane
> > > > mapping? The cross-ec-typec can provide orientation information and the
> > > > USB-C-aware controller will follow the lane mapping.
> > >
> > > I'm not really following but I don't think the DT binding discussed here
> > > prevents that.
> >
> > I'm thinking about:
> >
> > it6505 {
> >   orientation-switch;
> >
> >   ports {
> >     port@1 {
> >       it6505_dp_out: remote-endpoint = <&cros_ec_dp>;
> >       data-lanes = <0 1>;
> >     };
> >   };
> > };
> >
> > cros-ec {
> >   port {
> >     cross_ec_dp: remote-endpoint = <&it6505_dp_out>;
> >   };
> >
> >   connector@0 {
> >     reg = <0>;
> >     cros,dp-orientation = "normal";
> >
> >     ports {
> >       // all USB HS and SS ports as usual;
> >     };
> >   };
> >
> >   connector@1 {
> >     reg = <1>;
> >     cros,dp-orientation = "reverse";
> >
> >     ports {
> >       // all USB HS and SS ports as usual;
> >     };
> >   };
> >
> >   connector@2 {
> >     reg = <2>;
> >     cros,dp-orientation = "reverse";
> >
> >     ports {
> >       // all USB HS and SS ports as usual;
> >     };
> >   };
> >
> >   connector@3 {
> >     reg = <3>;
> >     cros,dp-orientation = "normal";
> >
> >     ports {
> >       // all USB HS and SS ports as usual;
> >     };
> >   };
> > };
> >
> > The cros-ec registers single drm bridge which will generate HPD events
> > except on Trogdor, etc. At the same time, cros-ec requests the
> > typec_switch_get(). When the cros-ec detects that the connector@N it
> > being used for DP, it just generates corresponding typec_switch_set()
> > call, setting the orientation of the it6505 (or QMP PHY). The rest can
> > be handled either by EC's HPD code or by DP's HPD handler, the
> > orientation should already be a correct one.
> >
> > So, yes. It requires adding the typec_switch_desc implementation _in_
> > the it6505 (or in any other component which handles the 0-1 or 2-3
> > selection). On the other hand as I wrote previously, the 0-1 / 2-3 is
> > the USB-C functionality, not the DP one.
> >
> 
> I don't think we should be adding typec code to pure display hardware
> drivers like IT6505. To keep the driver focused on display stuff I
> proposed implementing runtime lane assignment for drm_bridge chains
> because DP has lanes. My understanding is that not all display
> technologies have lanes, so implementing generic lane assignment
> functionality is overkill/incorrect. DP has physical lanes in hardware
> though, and those physical lanes are assigned to certain pins in the
> type-c DP altmode spec, so it's not overkill to think about lanes when
> the bridge is a DP bridge wired up to a type-c connector.

DisplayPort has fixed lanes assignment in the standard. So any driver
that reassigns / reallocates DisplayPort lanes dynamically implements
Type-C functionality.

> Long story short, I don't see how we can avoid _any_ lane assignment
> logic in drm_bridge. The logic shouldn't walk the entire bridge chain,
> but it should at least act on the bridge that is a DP bridge. I think
> you're saying pretty much the same thing here, but you want the lane
> remapping to be done via the typec layer whereas I want it to be done in
> the drm_bridge layer. To me it looks out of place to add a
> typec_switch_desc inside each DP drm_bridge because we duplicate the
> logic about USB type-c DP altmode lane assignment to each DP bridge. A
> DP bridge should just think about DP and not know or care about USB
> type-c.
> 
> This is what's leading me to think we need some sort of lane assignment
> capability at the DP connector. How that assignment flows from the DP
> connector created in drm_bridge_connector.c to the hardware is where it
> is less clear to me. Should that be implemented as a typec_switch_desc,
> essentially out of band with drm_bridge, or as some drm_bridge_funcs
> function similar to struct drm_bridge_funcs::hdmi_*()? If you look at
> IT6505 in it6505_get_extcon_property() it actually wants to pull the
> orientation of the type-c port with extcon_get_property(EXTCON_DISP_DP,
> EXTCON_PROP_USB_TYPEC_POLARITY). Maybe pushing the orientation to the DP
> bridge is backwards and we should be exposing this as some sort of
> connector API that the drm_bridge can query whenever it wants.

And it6505_get_extcon_property() / EXTCON_PROP_USB_TYPEC_POLARITY is a
Type-C code, isn't it?

> What about ANX7625 where two DP lanes go to a cross-point switch before
> leaving the chip on one of two pairs of lanes? This hardware is a DP
> bridge smashed together with an orientation switch (typec_switch_desc)
> so that you can simply wire the output pins up to a USB type-c connector
> and support 2 lanes DP altmode. Qualcomm's QMP phy is quite similar.
> Presumably we'd want the ANX driver to implement both a drm_bridge and a
> typec_switch_desc if it was directly connected to a usb-c-connector
> node. It's also interesting to think of the DT binding here, likely we
> would have one output port in the ANX node's graph that represents the
> combined DP and USB data that's connected to the SuperSpeed endpoint in
> the usb-c-connector.
> 
> In the case where two lanes are wired to one USB type-c connector and
> the other two lanes are wired to a different USB type-c connector it
> would be odd to keep the typec_switch_desc and figure out a way to
> mangle the lanes we want for a USB type-c connector by setting the
> orientation of the typec_switch_desc. The chip isn't really acting as a
> typec orientation control here because it isn't combining USB data and
> DP data for a single USB type-c port. In fact, the type-c port has an
> orientation and we actively don't want to tell the ANX7625 driver about
> that port orientation because the orientation control is implemented
> between the ANX part and the type-c connector by some redriver
> controlled by the EC.
> 
> To satisfy all these cases it almost feels like we need to make the DP
> connector have an "orientation", per your earlier DT snippet it would be
> "reversed" or "normal", even though in hardware a DP connector has no
> such concept because it can only be plugged in one way. All cases look
> to be covered if we say that the drm_connector can have an orientation,
> "normal" or "reversed", and we allow the bridge drivers to query that
> whenever they want with some bridge/connector API. The typical case will
> be that the orientation is normal, but we can make
> drm_connector_oob_hotplug_event() change that to "reversed" when the
> port is different.

The DP connector doesn't have the orientation, as you pointed out. Only
Type-C does.

> 
> This leaves us with the binding you propose above, and then some sort of
> property that indicates the orientation of the DP connector. Instead of
> being vendor specific I wonder if we can simply have a property like
> "dp-reverse-orientation" in the connector node that the displayport.c
> driver can look for to set the connector orientation to the reverse one
> when DP altmode is entered on the port.
> 
> This is what I have:
> 
>  it6505 {
>    ports {
>      port@1 {
>        it6505_dp_out: remote-endpoint = <&cros_ec_dp>;
>        data-lanes = <0 1>;
>      };
>    };
>  };
> 
>  cros-ec {
>    port {
>      cross_ec_dp: remote-endpoint = <&it6505_dp_out>;
>    };
> 
>    connector@0 {
>      reg = <0>;
> 
>      ports {
>        // all USB HS and SS ports as usual;
>      };
>    };
> 
>    connector@1 {
>      reg = <1>;
>      dp-reverse-orientation;
> 
>      ports {
>        // all USB HS and SS ports as usual;
>      };
>    };
> 
> or ANX, swap out for it6505 node:
> 
>  anx7625 {
>    ports {
>      port@1 {
>        anx7625_dp_out: remote-endpoint = <&cros_ec_dp>;
>        data-lanes = <0 1>;
>      };
>    };
>  };
> 
> and then a drm_bridge is created in cros-ec to terminate the bridge
> chain. The displayport altmode driver will find the drm_bridge and the
> drm_connector from the cros-ec node. When DP altmode is entered the
> displayport altmode driver will set the drm_connector orientation based
> on the presence of the dp-reverse-orientation property. We'll be able to
> hook the hpd_notify() path in cros-ec by adding code to the drm_bridge
> made there to do the HPD workaround. I'm not sure we need to use an
> auxiliary device in this case, because it's a one-off solution for
> cros-ec. And we don't even need to signal HPD from the cros-ec
> drm_bridge because the oob_hotplug event will do it for us. If anything,
> we need that displayport.c code to skip sending the hotplug event when
> "no-hpd" is present in the cros-ec node. Note, this works for any number
> of usb-c-connector nodes. And finally, DP bridges like IT6505 don't need
> to implement a typec_switch_desc, they can simply support flipping the
> orientation by querying the drm_connector for the bridge chain when they
> see fit. ANX7625 can support that as well when it doesn't see the
> 'orientation-switch' property.
> 
> Did I miss anything? I suspect a drm_connector having an orientation is
> the most controversial part of this proposal.

Yes... I understand that having orientation-switch handling in the DRM
driver sounds strange, but this is what we do in the QMP PHY driver. It
makes the code easier, as it keeps lane remapping local to the place
where it belongs - to the Type-C handlers.
Stephen Boyd Nov. 12, 2024, 2:16 a.m. UTC | #8
Quoting Dmitry Baryshkov (2024-11-08 23:05:18)
> On Thu, Nov 07, 2024 at 04:28:24PM -0800, Stephen Boyd wrote:
> > Quoting Dmitry Baryshkov (2024-10-31 15:54:49)
> > > On Thu, Oct 31, 2024 at 02:45:29PM -0700, Stephen Boyd wrote:
> > > > Quoting Dmitry Baryshkov (2024-10-31 11:42:36)
> > > > > On Tue, Oct 29, 2024 at 01:15:51PM -0700, Stephen Boyd wrote:
> > Long story short, I don't see how we can avoid _any_ lane assignment
> > logic in drm_bridge. The logic shouldn't walk the entire bridge chain,
> > but it should at least act on the bridge that is a DP bridge. I think
> > you're saying pretty much the same thing here, but you want the lane
> > remapping to be done via the typec layer whereas I want it to be done in
> > the drm_bridge layer. To me it looks out of place to add a
> > typec_switch_desc inside each DP drm_bridge because we duplicate the
> > logic about USB type-c DP altmode lane assignment to each DP bridge. A
> > DP bridge should just think about DP and not know or care about USB
> > type-c.
> >
> > This is what's leading me to think we need some sort of lane assignment
> > capability at the DP connector. How that assignment flows from the DP
> > connector created in drm_bridge_connector.c to the hardware is where it
> > is less clear to me. Should that be implemented as a typec_switch_desc,
> > essentially out of band with drm_bridge, or as some drm_bridge_funcs
> > function similar to struct drm_bridge_funcs::hdmi_*()? If you look at
> > IT6505 in it6505_get_extcon_property() it actually wants to pull the
> > orientation of the type-c port with extcon_get_property(EXTCON_DISP_DP,
> > EXTCON_PROP_USB_TYPEC_POLARITY). Maybe pushing the orientation to the DP
> > bridge is backwards and we should be exposing this as some sort of
> > connector API that the drm_bridge can query whenever it wants.
>
> And it6505_get_extcon_property() / EXTCON_PROP_USB_TYPEC_POLARITY is a
> Type-C code, isn't it?
>

Sort of? It's combining DP and USB_TYPEC enums there so it's not very
clear if it's one or the other instead of just both.

> > and then a drm_bridge is created in cros-ec to terminate the bridge
> > chain. The displayport altmode driver will find the drm_bridge and the
> > drm_connector from the cros-ec node. When DP altmode is entered the
> > displayport altmode driver will set the drm_connector orientation based
> > on the presence of the dp-reverse-orientation property. We'll be able to
> > hook the hpd_notify() path in cros-ec by adding code to the drm_bridge
> > made there to do the HPD workaround. I'm not sure we need to use an
> > auxiliary device in this case, because it's a one-off solution for
> > cros-ec. And we don't even need to signal HPD from the cros-ec
> > drm_bridge because the oob_hotplug event will do it for us. If anything,
> > we need that displayport.c code to skip sending the hotplug event when
> > "no-hpd" is present in the cros-ec node. Note, this works for any number
> > of usb-c-connector nodes. And finally, DP bridges like IT6505 don't need
> > to implement a typec_switch_desc, they can simply support flipping the
> > orientation by querying the drm_connector for the bridge chain when they
> > see fit. ANX7625 can support that as well when it doesn't see the
> > 'orientation-switch' property.
> >
> > Did I miss anything? I suspect a drm_connector having an orientation is
> > the most controversial part of this proposal.
>
> Yes... I understand that having orientation-switch handling in the DRM
> driver sounds strange, but this is what we do in the QMP PHY driver. It
> makes the code easier, as it keeps lane remapping local to the place
> where it belongs - to the Type-C handlers.
>

The QMP PHY is a type-c PHY, similar to ANX7625. It sits on the output
of the DP and USB PHYs and handles the type-c orientation and lane
merging for different USB type-c alternate modes. It's not a great
example of a plain DP bridge because it combines USB and USB type-c
features.

Either way, doing this through Type-C handlers is weird because the port
orientation in the Type-C framework is for the connector and there is an
orientation control hardware that handles the orientation already. For
example, with the IT6505 part on Corsola, the orientation is controlled
by a redriver part that the EC controls. It takes the DP and USB signals
and routes them to the correct pins on the usb-c-connector depending on
the cable orientation. The input side pinout is basically 2 or 4 lanes
DP and 2 lanes USB and the output side pinout is the USB type-c pinout
SSTXRX1 and SSTXRX2.

This redriver is equivalent to the QMP PHY type-c part. Maybe to bring
this example closer to QMP we can imagine if the QMP PHY was split into
two pairs of lanes, and the USB functionality wasn't used. The
orientation control for a usb-c-connector would be on a redriver that
takes 2 DP lanes from the QMP PHY as input. Saying that this QMP PHY is
the "orientation-switch" with that property in DT is confusing, because
it isn't controlling the orientation of the type-c port. The orientation
is handled by the redriver. That redriver may even be controlled by the
kernel as an orientation-switch.

I understand that the QMP PHY driver has implemented the lane control
for orientation with a typec_switch_desc, but the QMP PHY is a plain DP
PHY in this scenario. How would the type-c handlers work here? We
couldn't call them through the type-c framework as far as I can tell.

This is why I'm thinking the end of the bridge chain needs to have some
sort of orientation. If we had that then the place where the chain ends
and becomes muxed onto the usb-c-connector, i.e. the redriver, would be
where the DP bridge is told that it needs to flip the lanes. In the
cases I have, the redriver is the EC, and so we've combined them all
together in one node, cros-ec-typec. In the QMP PHY case the redriver is
the QMP PHY type-c part that sits on the DP and USB PHYs and sends their
signals out of the SoC.

Maybe the DT property in the ANX7625 or IT6505 node should be something
like "dp-orientation-switch" and then we have the type-c framework find
this property? Then we would need to add support for that property in
IT6505 using a typec_switch_desc, which is weird. I guess it all feels
like a hack because it's not always the case that the DP PHY is glued to
a USB type-c PHY.
Dmitry Baryshkov Nov. 15, 2024, 5:17 p.m. UTC | #9
On Mon, Nov 11, 2024 at 06:16:27PM -0800, Stephen Boyd wrote:
> Quoting Dmitry Baryshkov (2024-11-08 23:05:18)
> > On Thu, Nov 07, 2024 at 04:28:24PM -0800, Stephen Boyd wrote:
> > > Quoting Dmitry Baryshkov (2024-10-31 15:54:49)
> > > > On Thu, Oct 31, 2024 at 02:45:29PM -0700, Stephen Boyd wrote:
> > > > > Quoting Dmitry Baryshkov (2024-10-31 11:42:36)
> > > > > > On Tue, Oct 29, 2024 at 01:15:51PM -0700, Stephen Boyd wrote:
> > > Long story short, I don't see how we can avoid _any_ lane assignment
> > > logic in drm_bridge. The logic shouldn't walk the entire bridge chain,
> > > but it should at least act on the bridge that is a DP bridge. I think
> > > you're saying pretty much the same thing here, but you want the lane
> > > remapping to be done via the typec layer whereas I want it to be done in
> > > the drm_bridge layer. To me it looks out of place to add a
> > > typec_switch_desc inside each DP drm_bridge because we duplicate the
> > > logic about USB type-c DP altmode lane assignment to each DP bridge. A
> > > DP bridge should just think about DP and not know or care about USB
> > > type-c.
> > >
> > > This is what's leading me to think we need some sort of lane assignment
> > > capability at the DP connector. How that assignment flows from the DP
> > > connector created in drm_bridge_connector.c to the hardware is where it
> > > is less clear to me. Should that be implemented as a typec_switch_desc,
> > > essentially out of band with drm_bridge, or as some drm_bridge_funcs
> > > function similar to struct drm_bridge_funcs::hdmi_*()? If you look at
> > > IT6505 in it6505_get_extcon_property() it actually wants to pull the
> > > orientation of the type-c port with extcon_get_property(EXTCON_DISP_DP,
> > > EXTCON_PROP_USB_TYPEC_POLARITY). Maybe pushing the orientation to the DP
> > > bridge is backwards and we should be exposing this as some sort of
> > > connector API that the drm_bridge can query whenever it wants.
> >
> > And it6505_get_extcon_property() / EXTCON_PROP_USB_TYPEC_POLARITY is a
> > Type-C code, isn't it?
> >
> 
> Sort of? It's combining DP and USB_TYPEC enums there so it's not very
> clear if it's one or the other instead of just both.

But EXTCON_PROP_USB_TYPEC_POLARITY is just a Type-C, nothing about DP in it.

> 
> > > and then a drm_bridge is created in cros-ec to terminate the bridge
> > > chain. The displayport altmode driver will find the drm_bridge and the
> > > drm_connector from the cros-ec node. When DP altmode is entered the
> > > displayport altmode driver will set the drm_connector orientation based
> > > on the presence of the dp-reverse-orientation property. We'll be able to
> > > hook the hpd_notify() path in cros-ec by adding code to the drm_bridge
> > > made there to do the HPD workaround. I'm not sure we need to use an
> > > auxiliary device in this case, because it's a one-off solution for
> > > cros-ec. And we don't even need to signal HPD from the cros-ec
> > > drm_bridge because the oob_hotplug event will do it for us. If anything,
> > > we need that displayport.c code to skip sending the hotplug event when
> > > "no-hpd" is present in the cros-ec node. Note, this works for any number
> > > of usb-c-connector nodes. And finally, DP bridges like IT6505 don't need
> > > to implement a typec_switch_desc, they can simply support flipping the
> > > orientation by querying the drm_connector for the bridge chain when they
> > > see fit. ANX7625 can support that as well when it doesn't see the
> > > 'orientation-switch' property.
> > >
> > > Did I miss anything? I suspect a drm_connector having an orientation is
> > > the most controversial part of this proposal.
> >
> > Yes... I understand that having orientation-switch handling in the DRM
> > driver sounds strange, but this is what we do in the QMP PHY driver. It
> > makes the code easier, as it keeps lane remapping local to the place
> > where it belongs - to the Type-C handlers.
> >
> 
> The QMP PHY is a type-c PHY, similar to ANX7625. It sits on the output
> of the DP and USB PHYs and handles the type-c orientation and lane
> merging for different USB type-c alternate modes. It's not a great
> example of a plain DP bridge because it combines USB and USB type-c
> features.
> 
> Either way, doing this through Type-C handlers is weird because the port
> orientation in the Type-C framework is for the connector and there is an
> orientation control hardware that handles the orientation already. For
> example, with the IT6505 part on Corsola, the orientation is controlled
> by a redriver part that the EC controls. It takes the DP and USB signals
> and routes them to the correct pins on the usb-c-connector depending on
> the cable orientation. The input side pinout is basically 2 or 4 lanes
> DP and 2 lanes USB and the output side pinout is the USB type-c pinout
> SSTXRX1 and SSTXRX2.
> 
> This redriver is equivalent to the QMP PHY type-c part. Maybe to bring
> this example closer to QMP we can imagine if the QMP PHY was split into
> two pairs of lanes, and the USB functionality wasn't used. The
> orientation control for a usb-c-connector would be on a redriver that
> takes 2 DP lanes from the QMP PHY as input. Saying that this QMP PHY is
> the "orientation-switch" with that property in DT is confusing, because
> it isn't controlling the orientation of the type-c port. The orientation
> is handled by the redriver. That redriver may even be controlled by the
> kernel as an orientation-switch.

This is clear.

> 
> I understand that the QMP PHY driver has implemented the lane control
> for orientation with a typec_switch_desc, but the QMP PHY is a plain DP
> PHY in this scenario. How would the type-c handlers work here? We
> couldn't call them through the type-c framework as far as I can tell.

If QMP PHY is a plain DP PHY, it usually has no support for lane remapping
(e.g. phy-qcom-edp doesn't).

Let me reiterate, please: lane management is outside of the DisplayPort
spec, at least as far as I can understand it. All lane remapping
(especially a dynamic one) is a pure vendor extension to the standard.
I'm trying to find a way to support Corsola and Trogdor without adding
"this is done specially for Google" kind of API. Usually that doesn't
fly in the long term.

I understand that using Type-C API for the DRM bridge sounds strange.
But even the mentioned bridge uses Type-C API. It asks for the Type-C
polarity, not the DP polarity.

> This is why I'm thinking the end of the bridge chain needs to have some
> sort of orientation. If we had that then the place where the chain ends
> and becomes muxed onto the usb-c-connector, i.e. the redriver, would be
> where the DP bridge is told that it needs to flip the lanes. In the
> cases I have, the redriver is the EC, and so we've combined them all
> together in one node, cros-ec-typec. In the QMP PHY case the redriver is
> the QMP PHY type-c part that sits on the DP and USB PHYs and sends their
> signals out of the SoC.
> 
> Maybe the DT property in the ANX7625 or IT6505 node should be something
> like "dp-orientation-switch" and then we have the type-c framework find
> this property? Then we would need to add support for that property in
> IT6505 using a typec_switch_desc, which is weird. I guess it all feels
> like a hack because it's not always the case that the DP PHY is glued to
> a USB type-c PHY.

I think just "orientation-switch" is enough. In the end it's not a
"typec-orientation-switch".
Stephen Boyd Nov. 20, 2024, 1:09 a.m. UTC | #10
Quoting Dmitry Baryshkov (2024-11-15 09:17:15)
> On Mon, Nov 11, 2024 at 06:16:27PM -0800, Stephen Boyd wrote:
> > Quoting Dmitry Baryshkov (2024-11-08 23:05:18)
> > > On Thu, Nov 07, 2024 at 04:28:24PM -0800, Stephen Boyd wrote:
> > > > Quoting Dmitry Baryshkov (2024-10-31 15:54:49)
> > > > > On Thu, Oct 31, 2024 at 02:45:29PM -0700, Stephen Boyd wrote:
> > > > > > Quoting Dmitry Baryshkov (2024-10-31 11:42:36)
> > > > > > > On Tue, Oct 29, 2024 at 01:15:51PM -0700, Stephen Boyd wrote:
> > > > Long story short, I don't see how we can avoid _any_ lane assignment
> > > > logic in drm_bridge. The logic shouldn't walk the entire bridge chain,
> > > > but it should at least act on the bridge that is a DP bridge. I think
> > > > you're saying pretty much the same thing here, but you want the lane
> > > > remapping to be done via the typec layer whereas I want it to be done in
> > > > the drm_bridge layer. To me it looks out of place to add a
> > > > typec_switch_desc inside each DP drm_bridge because we duplicate the
> > > > logic about USB type-c DP altmode lane assignment to each DP bridge. A
> > > > DP bridge should just think about DP and not know or care about USB
> > > > type-c.
> > > >
> > > > This is what's leading me to think we need some sort of lane assignment
> > > > capability at the DP connector. How that assignment flows from the DP
> > > > connector created in drm_bridge_connector.c to the hardware is where it
> > > > is less clear to me. Should that be implemented as a typec_switch_desc,
> > > > essentially out of band with drm_bridge, or as some drm_bridge_funcs
> > > > function similar to struct drm_bridge_funcs::hdmi_*()? If you look at
> > > > IT6505 in it6505_get_extcon_property() it actually wants to pull the
> > > > orientation of the type-c port with extcon_get_property(EXTCON_DISP_DP,
> > > > EXTCON_PROP_USB_TYPEC_POLARITY). Maybe pushing the orientation to the DP
> > > > bridge is backwards and we should be exposing this as some sort of
> > > > connector API that the drm_bridge can query whenever it wants.
> > >
> > > And it6505_get_extcon_property() / EXTCON_PROP_USB_TYPEC_POLARITY is a
> > > Type-C code, isn't it?
> > >
> >
> > Sort of? It's combining DP and USB_TYPEC enums there so it's not very
> > clear if it's one or the other instead of just both.
>
> But EXTCON_PROP_USB_TYPEC_POLARITY is just a Type-C, nothing about DP in it.

It's extcon_get_property(it6505->extcon, EXTCON_DISP_DP,
EXTCON_PROP_USB_TYPEC_POLARITY, ...) which has EXTCON_DISP_DP in there,
so there's something about DP there. That's all I'm saying.

> >
> > I understand that the QMP PHY driver has implemented the lane control
> > for orientation with a typec_switch_desc, but the QMP PHY is a plain DP
> > PHY in this scenario. How would the type-c handlers work here? We
> > couldn't call them through the type-c framework as far as I can tell.
>
> If QMP PHY is a plain DP PHY, it usually has no support for lane remapping
> (e.g. phy-qcom-edp doesn't).
>
> Let me reiterate, please: lane management is outside of the DisplayPort
> spec, at least as far as I can understand it. All lane remapping
> (especially a dynamic one) is a pure vendor extension to the standard.
> I'm trying to find a way to support Corsola and Trogdor without adding
> "this is done specially for Google" kind of API. Usually that doesn't
> fly in the long term.

Got it.

>
> I understand that using Type-C API for the DRM bridge sounds strange.
> But even the mentioned bridge uses Type-C API. It asks for the Type-C
> polarity, not the DP polarity.
>

I understand that lane assignment isn't part of the DisplayPort spec,
while it is part of the USB Type-C DisplayPort Altmode spec.

I'm not entirely convinced that lane assignment is _only_ part of the
altmode spec and should be implemented with a typec switch though,
because I imagine some hardware design could be created that has two
DisplayPort connectors, just like these two USB-C connectors, and some
sort of HPD redriver logic similar to the EC that decides which DP port
"wins" and should have DP sent to it. Or perhaps 2 lanes DP to a DP
connector and 2 lanes DP sent to a DP to HDMI bridge (shudder). In
either case, USB type-c isn't involved.

It sounds like we're debating how to handle lane assignment in the
kernel. Either way, the code is going to be implemented in the bridge
driver because it's the one that has to change what physical lane a
logical lane is assigned to. The question is if it should be some sort
of bridge_funcs callback, or should bridge drivers hook into the typec
framework to expose an orientation switch, or something else?

I'm thinking we should introduce some sort of bridge_funcs callback that
can be called from the DP altmode driver, either parallel to the
drm_connector_oob_hotplug_event() function or from it directly. If we
can pass the fwnode for the usb-c-connector to the oob_hotplug_event
callback, maybe that's all we need to figure out which lanes go where.
And then in the 2 DP connector muxing world we can call
drm_connector_oob_hotplug_event() with one or the other DP connector
node, which will likely be children nodes of the "HPD redriver" device.
Dmitry Baryshkov Nov. 21, 2024, 10:59 p.m. UTC | #11
On Tue, Nov 19, 2024 at 08:09:31PM -0500, Stephen Boyd wrote:
> Quoting Dmitry Baryshkov (2024-11-15 09:17:15)
> > On Mon, Nov 11, 2024 at 06:16:27PM -0800, Stephen Boyd wrote:
> > > Quoting Dmitry Baryshkov (2024-11-08 23:05:18)
> > > > On Thu, Nov 07, 2024 at 04:28:24PM -0800, Stephen Boyd wrote:
> > > > > Quoting Dmitry Baryshkov (2024-10-31 15:54:49)
> > > > > > On Thu, Oct 31, 2024 at 02:45:29PM -0700, Stephen Boyd wrote:
> > > > > > > Quoting Dmitry Baryshkov (2024-10-31 11:42:36)
> > > > > > > > On Tue, Oct 29, 2024 at 01:15:51PM -0700, Stephen Boyd wrote:
> > > > > Long story short, I don't see how we can avoid _any_ lane assignment
> > > > > logic in drm_bridge. The logic shouldn't walk the entire bridge chain,
> > > > > but it should at least act on the bridge that is a DP bridge. I think
> > > > > you're saying pretty much the same thing here, but you want the lane
> > > > > remapping to be done via the typec layer whereas I want it to be done in
> > > > > the drm_bridge layer. To me it looks out of place to add a
> > > > > typec_switch_desc inside each DP drm_bridge because we duplicate the
> > > > > logic about USB type-c DP altmode lane assignment to each DP bridge. A
> > > > > DP bridge should just think about DP and not know or care about USB
> > > > > type-c.
> > > > >
> > > > > This is what's leading me to think we need some sort of lane assignment
> > > > > capability at the DP connector. How that assignment flows from the DP
> > > > > connector created in drm_bridge_connector.c to the hardware is where it
> > > > > is less clear to me. Should that be implemented as a typec_switch_desc,
> > > > > essentially out of band with drm_bridge, or as some drm_bridge_funcs
> > > > > function similar to struct drm_bridge_funcs::hdmi_*()? If you look at
> > > > > IT6505 in it6505_get_extcon_property() it actually wants to pull the
> > > > > orientation of the type-c port with extcon_get_property(EXTCON_DISP_DP,
> > > > > EXTCON_PROP_USB_TYPEC_POLARITY). Maybe pushing the orientation to the DP
> > > > > bridge is backwards and we should be exposing this as some sort of
> > > > > connector API that the drm_bridge can query whenever it wants.
> > > >
> > > > And it6505_get_extcon_property() / EXTCON_PROP_USB_TYPEC_POLARITY is a
> > > > Type-C code, isn't it?
> > > >
> > >
> > > Sort of? It's combining DP and USB_TYPEC enums there so it's not very
> > > clear if it's one or the other instead of just both.
> >
> > But EXTCON_PROP_USB_TYPEC_POLARITY is just a Type-C, nothing about DP in it.
> 
> It's extcon_get_property(it6505->extcon, EXTCON_DISP_DP,
> EXTCON_PROP_USB_TYPEC_POLARITY, ...) which has EXTCON_DISP_DP in there,
> so there's something about DP there. That's all I'm saying.
> 
> > >
> > > I understand that the QMP PHY driver has implemented the lane control
> > > for orientation with a typec_switch_desc, but the QMP PHY is a plain DP
> > > PHY in this scenario. How would the type-c handlers work here? We
> > > couldn't call them through the type-c framework as far as I can tell.
> >
> > If QMP PHY is a plain DP PHY, it usually has no support for lane remapping
> > (e.g. phy-qcom-edp doesn't).
> >
> > Let me reiterate, please: lane management is outside of the DisplayPort
> > spec, at least as far as I can understand it. All lane remapping
> > (especially a dynamic one) is a pure vendor extension to the standard.
> > I'm trying to find a way to support Corsola and Trogdor without adding
> > "this is done specially for Google" kind of API. Usually that doesn't
> > fly in the long term.
> 
> Got it.
> 
> >
> > I understand that using Type-C API for the DRM bridge sounds strange.
> > But even the mentioned bridge uses Type-C API. It asks for the Type-C
> > polarity, not the DP polarity.
> >
> 
> I understand that lane assignment isn't part of the DisplayPort spec,
> while it is part of the USB Type-C DisplayPort Altmode spec.
> 
> I'm not entirely convinced that lane assignment is _only_ part of the
> altmode spec

just to clarify: I'm only talking about a dynamic lane management here.
If the DP bridge hardware supports remapping lanes in a weird way and
board designers decided to use that "feature", then having a property
linke data-lanes = <2 1 3 0>; makes perfect sense to me.

> and should be implemented with a typec switch though,
> because I imagine some hardware design could be created that has two
> DisplayPort connectors, just like these two USB-C connectors, and some
> sort of HPD redriver logic similar to the EC that decides which DP port
> "wins" and should have DP sent to it. Or perhaps 2 lanes DP to a DP
> connector and 2 lanes DP sent to a DP to HDMI bridge (shudder). In
> either case, USB type-c isn't involved.

/me keeps fingers crossed that hw designers won't do such a thing

But I see your point.

> 
> It sounds like we're debating how to handle lane assignment in the
> kernel. Either way, the code is going to be implemented in the bridge
> driver because it's the one that has to change what physical lane a
> logical lane is assigned to. The question is if it should be some sort
> of bridge_funcs callback, or should bridge drivers hook into the typec
> framework to expose an orientation switch, or something else?

I was assuming that orientation switch is such kind of a hook.

> 
> I'm thinking we should introduce some sort of bridge_funcs callback that
> can be called from the DP altmode driver, either parallel to the
> drm_connector_oob_hotplug_event() function or from it directly. If we
> can pass the fwnode for the usb-c-connector to the oob_hotplug_event
> callback, maybe that's all we need to figure out which lanes go where.
> And then in the 2 DP connector muxing world we can call
> drm_connector_oob_hotplug_event() with one or the other DP connector
> node, which will likely be children nodes of the "HPD redriver" device.

If you call it from drm_bridge_connector's oob_hotplug_event handler,
this should fly. Does it cover your 3-DP or 4-DP usecases?
Stephen Boyd Dec. 3, 2024, 11:50 p.m. UTC | #12
Quoting Dmitry Baryshkov (2024-11-21 14:59:42)
> On Tue, Nov 19, 2024 at 08:09:31PM -0500, Stephen Boyd wrote:
> >
> > It sounds like we're debating how to handle lane assignment in the
> > kernel. Either way, the code is going to be implemented in the bridge
> > driver because it's the one that has to change what physical lane a
> > logical lane is assigned to. The question is if it should be some sort
> > of bridge_funcs callback, or should bridge drivers hook into the typec
> > framework to expose an orientation switch, or something else?
>
> I was assuming that orientation switch is such kind of a hook.
>
> >
> > I'm thinking we should introduce some sort of bridge_funcs callback that
> > can be called from the DP altmode driver, either parallel to the
> > drm_connector_oob_hotplug_event() function or from it directly. If we
> > can pass the fwnode for the usb-c-connector to the oob_hotplug_event
> > callback, maybe that's all we need to figure out which lanes go where.
> > And then in the 2 DP connector muxing world we can call
> > drm_connector_oob_hotplug_event() with one or the other DP connector
> > node, which will likely be children nodes of the "HPD redriver" device.
>
> If you call it from drm_bridge_connector's oob_hotplug_event handler,
> this should fly. Does it cover your 3-DP or 4-DP usecases?
>

I think it will work as long as we're able to add some sort of property
to the usb-c-connector node to indicate that the DP lanes are flipped.
It feels like that should be in the displayport altmode node to keep
things tidy because the SuperSpeed port is overloaded. Maybe the drm
framework can have some API that can take the fwnode from the
oob_hotplug_event handler and tell the bridge driver which way the
orientation is.

 connector {
   compatible = "usb-c-connector";

   altmodes {
     displayport {
       orientation-reversed;
     }
   };

   ports {
     ...
   };
 };


 int drm_dp_typec_orientation_flipped(struct fwnode_handle *fwnode)
 {
   struct fwnode_handle *altmodes;
   struct fwnode_handle *dp;

   altmodes = fwnode_get_named_child_node(fwnode, "altmodes");
   if (!altmodes)
     return -EINVAL;

   dp = fwnode_get_named_child_node(altmodes, "displayport");
   if (!dp)
     return -EINVAL;

   if (fwnode_property_read_bool(dp, "orientation-reversed"))
     return 1;

   return 0;
 }

There's another wrinkle on some Corsola devices where the EC says
there's a usb-c-connector on the board, but in reality the DP lanes are
connected to a DP-to-HDMI bridge that is controlled by the EC which goes
to an HDMI connector on the side of the laptop. The EC does the
arbitration as usual because there's only one DP source and one or two
usb type-c connectors physically on the laptop in addition to the HDMI
connector.

The easiest way to imagine this is that we took the usb-c-connector and
jammed an HDMI dongle in there with some glue so that it can never be
removed. There isn't any USB going there either because it can't be
used. I suppose we can continue to describe this with an
altmodes/displayport node but then add some compatible like
"usb-c-hdmi-connector" or another property to the altmodes/displayport
node like "type = hdmi" that signifies this is a connector that only
outputs HDMI.
Dmitry Baryshkov Dec. 5, 2024, 6:47 p.m. UTC | #13
On Tue, Dec 03, 2024 at 03:50:58PM -0800, Stephen Boyd wrote:
> Quoting Dmitry Baryshkov (2024-11-21 14:59:42)
> > On Tue, Nov 19, 2024 at 08:09:31PM -0500, Stephen Boyd wrote:
> > >
> > > It sounds like we're debating how to handle lane assignment in the
> > > kernel. Either way, the code is going to be implemented in the bridge
> > > driver because it's the one that has to change what physical lane a
> > > logical lane is assigned to. The question is if it should be some sort
> > > of bridge_funcs callback, or should bridge drivers hook into the typec
> > > framework to expose an orientation switch, or something else?
> >
> > I was assuming that orientation switch is such kind of a hook.
> >
> > >
> > > I'm thinking we should introduce some sort of bridge_funcs callback that
> > > can be called from the DP altmode driver, either parallel to the
> > > drm_connector_oob_hotplug_event() function or from it directly. If we
> > > can pass the fwnode for the usb-c-connector to the oob_hotplug_event
> > > callback, maybe that's all we need to figure out which lanes go where.
> > > And then in the 2 DP connector muxing world we can call
> > > drm_connector_oob_hotplug_event() with one or the other DP connector
> > > node, which will likely be children nodes of the "HPD redriver" device.
> >
> > If you call it from drm_bridge_connector's oob_hotplug_event handler,
> > this should fly. Does it cover your 3-DP or 4-DP usecases?
> >
> 
> I think it will work as long as we're able to add some sort of property
> to the usb-c-connector node to indicate that the DP lanes are flipped.
> It feels like that should be in the displayport altmode node to keep
> things tidy because the SuperSpeed port is overloaded. Maybe the drm
> framework can have some API that can take the fwnode from the
> oob_hotplug_event handler and tell the bridge driver which way the
> orientation is.
> 
>  connector {
>    compatible = "usb-c-connector";
> 
>    altmodes {
>      displayport {
>        orientation-reversed;
>      }
>    };
> 
>    ports {
>      ...
>    };
>  };
> 
> 
>  int drm_dp_typec_orientation_flipped(struct fwnode_handle *fwnode)
>  {
>    struct fwnode_handle *altmodes;
>    struct fwnode_handle *dp;
> 
>    altmodes = fwnode_get_named_child_node(fwnode, "altmodes");
>    if (!altmodes)
>      return -EINVAL;
> 
>    dp = fwnode_get_named_child_node(altmodes, "displayport");
>    if (!dp)
>      return -EINVAL;
> 
>    if (fwnode_property_read_bool(dp, "orientation-reversed"))
>      return 1;

If that passes through DT maintainers, that's fine with me.

> 
>    return 0;
>  }
> 
> There's another wrinkle on some Corsola devices where the EC says
> there's a usb-c-connector on the board, but in reality the DP lanes are
> connected to a DP-to-HDMI bridge that is controlled by the EC which goes
> to an HDMI connector on the side of the laptop. The EC does the
> arbitration as usual because there's only one DP source and one or two
> usb type-c connectors physically on the laptop in addition to the HDMI
> connector.
> 
> The easiest way to imagine this is that we took the usb-c-connector and
> jammed an HDMI dongle in there with some glue so that it can never be
> removed. There isn't any USB going there either because it can't be
> used. I suppose we can continue to describe this with an
> altmodes/displayport node but then add some compatible like
> "usb-c-hdmi-connector" or another property to the altmodes/displayport
> node like "type = hdmi" that signifies this is a connector that only
> outputs HDMI.

Does that DP-to-HDMI bridge talk USB-C or just pure DP? In other words,
will it be properly discovered and handled if we just leave it as a
weird usb-c-connector (maybe with an additional annotation, we have
USB_PORT_CONNECT_TYPE_HARD_WIRED for USB ports, we might have something
similar for Type-C connectors).
Stephen Boyd Dec. 11, 2024, 9:11 p.m. UTC | #14
Quoting Dmitry Baryshkov (2024-12-05 10:47:08)
> On Tue, Dec 03, 2024 at 03:50:58PM -0800, Stephen Boyd wrote:
> >
> > The easiest way to imagine this is that we took the usb-c-connector and
> > jammed an HDMI dongle in there with some glue so that it can never be
> > removed. There isn't any USB going there either because it can't be
> > used. I suppose we can continue to describe this with an
> > altmodes/displayport node but then add some compatible like
> > "usb-c-hdmi-connector" or another property to the altmodes/displayport
> > node like "type = hdmi" that signifies this is a connector that only
> > outputs HDMI.
>
> Does that DP-to-HDMI bridge talk USB-C or just pure DP? In other words,
> will it be properly discovered and handled if we just leave it as a
> weird usb-c-connector (maybe with an additional annotation, we have
> USB_PORT_CONNECT_TYPE_HARD_WIRED for USB ports, we might have something
> similar for Type-C connectors).

It is pure DP. Maybe we can have a google,cros-ec-usbc-hdmi compatible
string here because this is a weird design.
Dmitry Baryshkov Dec. 11, 2024, 9:16 p.m. UTC | #15
On Wed, 11 Dec 2024 at 23:11, Stephen Boyd <swboyd@chromium.org> wrote:
>
> Quoting Dmitry Baryshkov (2024-12-05 10:47:08)
> > On Tue, Dec 03, 2024 at 03:50:58PM -0800, Stephen Boyd wrote:
> > >
> > > The easiest way to imagine this is that we took the usb-c-connector and
> > > jammed an HDMI dongle in there with some glue so that it can never be
> > > removed. There isn't any USB going there either because it can't be
> > > used. I suppose we can continue to describe this with an
> > > altmodes/displayport node but then add some compatible like
> > > "usb-c-hdmi-connector" or another property to the altmodes/displayport
> > > node like "type = hdmi" that signifies this is a connector that only
> > > outputs HDMI.
> >
> > Does that DP-to-HDMI bridge talk USB-C or just pure DP? In other words,
> > will it be properly discovered and handled if we just leave it as a
> > weird usb-c-connector (maybe with an additional annotation, we have
> > USB_PORT_CONNECT_TYPE_HARD_WIRED for USB ports, we might have something
> > similar for Type-C connectors).
>
> It is pure DP. Maybe we can have a google,cros-ec-usbc-hdmi compatible
> string here because this is a weird design.

Just google,cros-ec-hdmi for the corresponding connector?
Stephen Boyd Dec. 11, 2024, 9:21 p.m. UTC | #16
Quoting Dmitry Baryshkov (2024-12-11 13:16:56)
> On Wed, 11 Dec 2024 at 23:11, Stephen Boyd <swboyd@chromium.org> wrote:
> >
> > It is pure DP. Maybe we can have a google,cros-ec-usbc-hdmi compatible
> > string here because this is a weird design.
>
> Just google,cros-ec-hdmi for the corresponding connector?
>

Sure.
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
index c991626dc22b..bbe28047d0c0 100644
--- a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
+++ b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
@@ -98,9 +98,6 @@  properties:
 
   gpio-controller: true
 
-  typec:
-    $ref: /schemas/usb/google,cros-ec-typec.yaml#
-
   ec-pwm:
     $ref: /schemas/pwm/google,cros-ec-pwm.yaml#
     deprecated: true
@@ -166,6 +163,10 @@  patternProperties:
     type: object
     $ref: /schemas/extcon/extcon-usbc-cros-ec.yaml#
 
+  "^typec(-[0-9])*$":
+    type: object
+    $ref: /schemas/usb/google,cros-ec-typec.yaml#
+
 required:
   - compatible
 
diff --git a/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml b/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml
index 365523a63179..235b86da3cdd 100644
--- a/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml
+++ b/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml
@@ -26,6 +26,106 @@  properties:
   '#size-cells':
     const: 0
 
+  mux-gpios:
+    description: GPIOs indicating which way the DP mux is steered
+    maxItems: 1
+
+  no-hpd:
+    description: Indicates this endpoint doesn't signal HPD for DisplayPort
+    type: boolean
+
+  mode-switch:
+    $ref: usb-switch.yaml#properties/mode-switch
+
+  orientation-switch:
+    $ref: usb-switch.yaml#properties/orientation-switch
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
+        description: Output ports for combined DP and USB SS data
+        patternProperties:
+          "^endpoint@([0-8])$":
+            $ref: usb-switch.yaml#/$defs/usbc-out-endpoint
+            unevaluatedProperties: false
+
+        anyOf:
+          - required:
+              - endpoint@0
+          - required:
+              - endpoint@1
+          - required:
+              - endpoint@2
+          - required:
+              - endpoint@3
+          - required:
+              - endpoint@4
+          - required:
+              - endpoint@5
+          - required:
+              - endpoint@6
+          - required:
+              - endpoint@7
+          - required:
+              - endpoint@8
+
+      port@1:
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
+        description:
+          Input port to receive USB SuperSpeed (SS) data
+        patternProperties:
+          "^endpoint@([0-8])$":
+            $ref: usb-switch.yaml#/$defs/usbc-in-endpoint
+            unevaluatedProperties: false
+
+        anyOf:
+          - required:
+              - endpoint@0
+          - required:
+              - endpoint@1
+          - required:
+              - endpoint@2
+          - required:
+              - endpoint@3
+          - required:
+              - endpoint@4
+          - required:
+              - endpoint@5
+          - required:
+              - endpoint@6
+          - required:
+              - endpoint@7
+          - required:
+              - endpoint@8
+
+      port@2:
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        description:
+          Input port to receive DisplayPort (DP) data
+        unevaluatedProperties: false
+
+        properties:
+          endpoint:
+            $ref: usb-switch.yaml#/$defs/dp-endpoint
+            unevaluatedProperties: false
+
+        required:
+          - endpoint
+
+    required:
+      - port@0
+
+    anyOf:
+      - required:
+          - port@1
+      - required:
+          - port@2
+
 patternProperties:
   '^connector@[0-9a-f]+$':
     $ref: /schemas/connector/usb-connector.yaml#
@@ -35,6 +135,40 @@  patternProperties:
 required:
   - compatible
 
+allOf:
+  - if:
+      required:
+        - no-hpd
+    then:
+      properties:
+        ports:
+          required:
+            - port@2
+  - if:
+      required:
+        - mux-gpios
+    then:
+      properties:
+        ports:
+          required:
+            - port@2
+  - if:
+      required:
+        - orientation-switch
+    then:
+      properties:
+        ports:
+          required:
+            - port@2
+  - if:
+      required:
+        - mode-switch
+    then:
+      properties:
+        ports:
+          required:
+            - port@2
+
 additionalProperties: false
 
 examples:
@@ -50,6 +184,8 @@  examples:
 
         typec {
           compatible = "google,cros-ec-typec";
+          orientation-switch;
+          mode-switch;
 
           #address-cells = <1>;
           #size-cells = <0>;
@@ -60,6 +196,99 @@  examples:
             power-role = "dual";
             data-role = "dual";
             try-power-role = "source";
+
+            ports {
+              #address-cells = <1>;
+              #size-cells = <0>;
+
+              port@0 {
+                reg = <0>;
+                usb_c0_hs: endpoint {
+                  remote-endpoint = <&usb_hub_dfp3_hs>;
+                };
+              };
+
+              port@1 {
+                reg = <1>;
+                usb_c0_ss: endpoint {
+                  remote-endpoint = <&cros_typec_c0_ss>;
+                };
+              };
+            };
+          };
+
+          connector@1 {
+            compatible = "usb-c-connector";
+            reg = <1>;
+            power-role = "dual";
+            data-role = "dual";
+            try-power-role = "source";
+
+            ports {
+              #address-cells = <1>;
+              #size-cells = <0>;
+
+              port@0 {
+                reg = <0>;
+                usb_c1_hs: endpoint {
+                  remote-endpoint = <&usb_hub_dfp2_hs>;
+                };
+              };
+
+              port@1 {
+                reg = <1>;
+                usb_c1_ss: endpoint {
+                  remote-endpoint = <&cros_typec_c1_ss>;
+                };
+              };
+            };
+          };
+
+          ports {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            port@0 {
+              reg = <0>;
+              #address-cells = <1>;
+              #size-cells = <0>;
+
+              cros_typec_c0_ss: endpoint@0 {
+                reg = <0>;
+                remote-endpoint = <&usb_c0_ss>;
+                data-lanes = <0 1 2 3>;
+              };
+
+              cros_typec_c1_ss: endpoint@1 {
+                reg = <1>;
+                remote-endpoint = <&usb_c1_ss>;
+                data-lanes = <2 3 0 1>;
+              };
+            };
+
+            port@1 {
+              reg = <1>;
+              #address-cells = <1>;
+              #size-cells = <0>;
+
+              usb_in_0: endpoint@0 {
+                reg = <0>;
+                remote-endpoint = <&usb_ss_0_out>;
+              };
+
+              usb_in_1: endpoint@1 {
+                reg = <1>;
+                remote-endpoint = <&usb_ss_1_out>;
+              };
+            };
+
+            port@2 {
+              reg = <2>;
+              dp_in: endpoint {
+                remote-endpoint = <&dp_phy>;
+                data-lanes = <0 1>;
+              };
+            };
           };
         };
       };