| Message ID | 20240126-dev-rx-enable-v4-3-45aaf4d96328@theobroma-systems.com |
|---|---|
| State | New |
| Headers | show |
| Series | serial: 8250: Add support for rs485 half/full duplex on puma/ringneck-haikou | expand |
On Fri, Jan 26, 2024 at 03:55:12PM +0100, Farouk Bouabid wrote: > RS485 can have a receiver-enable gpio (rx-enable-gpios). When rs485 is > enabled, this gpio, if provided, must be driven active while receiving. > However when RS485 is disabled this gpio should not have an undefined > state. In that case, as DE and RE pins can be connected both to this gpio, > if its state is not properly defined, can cause unexpected transceiver > behavior. > This binding depend on rx-enable-gpios to be implemented. Why do you need a dedicated property for this when there exists a device specific compatible for the uart on both of the affected rockchip systems? Thanks, Conor. > > Signed-off-by: Farouk Bouabid <farouk.bouabid@theobroma-systems.com> > --- > Documentation/devicetree/bindings/serial/rs485.yaml | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/Documentation/devicetree/bindings/serial/rs485.yaml b/Documentation/devicetree/bindings/serial/rs485.yaml > index b64577036b5c..4c79dfaaf460 100644 > --- a/Documentation/devicetree/bindings/serial/rs485.yaml > +++ b/Documentation/devicetree/bindings/serial/rs485.yaml > @@ -55,6 +55,11 @@ properties: > description: GPIO to handle a separate RS485 receive enable signal > maxItems: 1 > > + rs485-rx-enable-inactive-when-rs485-disabled: > + description: rx-enable GPIO is not active when RS485 is disabled. If missing, active-state > + is assumed. > + $ref: /schemas/types.yaml#/definitions/flag > + > rs485-term-gpios: > description: GPIO pin to enable RS485 bus termination. > maxItems: 1 > > -- > 2.34.1 >
Hi Conor, On 1/28/24 18:38, Conor Dooley wrote: > On Fri, Jan 26, 2024 at 03:55:12PM +0100, Farouk Bouabid wrote: >> RS485 can have a receiver-enable gpio (rx-enable-gpios). When rs485 is >> enabled, this gpio, if provided, must be driven active while receiving. >> However when RS485 is disabled this gpio should not have an undefined >> state. In that case, as DE and RE pins can be connected both to this gpio, >> if its state is not properly defined, can cause unexpected transceiver >> behavior. >> This binding depend on rx-enable-gpios to be implemented. > > Why do you need a dedicated property for this when there exists a device > specific compatible for the uart on both of the affected rockchip > systems? > This has nothing to do with Rockchip's IP but the HW design of our carrierboard, so using the "rockchip,px30-uart" for that (which I assume is what was suggested here?) is incorrect since it'll also apply to PX30, RK3399 and RK3588-based Q7 SoCs we manufacture. Did I understand the suggestion correctly? Cheers, Quentin
On Mon, Jan 29, 2024 at 01:26:51PM +0100, Quentin Schulz wrote: > Hi Conor, > > On 1/28/24 18:38, Conor Dooley wrote: > > On Fri, Jan 26, 2024 at 03:55:12PM +0100, Farouk Bouabid wrote: > > > RS485 can have a receiver-enable gpio (rx-enable-gpios). When rs485 is > > > enabled, this gpio, if provided, must be driven active while receiving. > > > However when RS485 is disabled this gpio should not have an undefined > > > state. In that case, as DE and RE pins can be connected both to this gpio, > > > if its state is not properly defined, can cause unexpected transceiver > > > behavior. > > > This binding depend on rx-enable-gpios to be implemented. > > > > Why do you need a dedicated property for this when there exists a device > > specific compatible for the uart on both of the affected rockchip > > systems? > > > > This has nothing to do with Rockchip's IP but the HW design of our > carrierboard, so using the "rockchip,px30-uart" for that (which I assume is > what was suggested here?) is incorrect since it'll also apply to PX30, > RK3399 and RK3588-based Q7 SoCs we manufacture. > > Did I understand the suggestion correctly? Yes you did. That explanation for not being able to use the compatibles makes sense. However, I can't give you an ack, because reading the commit message gives me the same feeling as looking at this photo: https://www.reddit.com/r/pics/comments/f8jyuz/nothing_in_this_image_is_identifiable/ Sorry, Conor.
diff --git a/Documentation/devicetree/bindings/serial/rs485.yaml b/Documentation/devicetree/bindings/serial/rs485.yaml index b64577036b5c..4c79dfaaf460 100644 --- a/Documentation/devicetree/bindings/serial/rs485.yaml +++ b/Documentation/devicetree/bindings/serial/rs485.yaml @@ -55,6 +55,11 @@ properties: description: GPIO to handle a separate RS485 receive enable signal maxItems: 1 + rs485-rx-enable-inactive-when-rs485-disabled: + description: rx-enable GPIO is not active when RS485 is disabled. If missing, active-state + is assumed. + $ref: /schemas/types.yaml#/definitions/flag + rs485-term-gpios: description: GPIO pin to enable RS485 bus termination. maxItems: 1
RS485 can have a receiver-enable gpio (rx-enable-gpios). When rs485 is enabled, this gpio, if provided, must be driven active while receiving. However when RS485 is disabled this gpio should not have an undefined state. In that case, as DE and RE pins can be connected both to this gpio, if its state is not properly defined, can cause unexpected transceiver behavior. This binding depend on rx-enable-gpios to be implemented. Signed-off-by: Farouk Bouabid <farouk.bouabid@theobroma-systems.com> --- Documentation/devicetree/bindings/serial/rs485.yaml | 5 +++++ 1 file changed, 5 insertions(+)