diff mbox series

[v2,2/3] usb: chipidea: Hook into mux framework to toggle usb switch

Message ID 20170714214005.14967-3-stephen.boyd@linaro.org
State New
Headers show
Series [v2,1/3] mux: Add mux_control_get_optional() API | expand

Commit Message

Stephen Boyd July 14, 2017, 9:40 p.m. UTC 
On the db410c 96boards platform we have a TC7USB40MU on the board
to mux the D+/D- lines coming from the controller between a micro
usb "device" port and a USB hub for "host" roles[1]. During a
role switch, we need to toggle this mux to forward the D+/D-
lines to either the port or the hub. Add the necessary code to do
the role switch in chipidea core via the generic mux framework.
Board configurations like on db410c are expected to change roles
via the sysfs API described in
Documentation/ABI/testing/sysfs-platform-chipidea-usb2.

[1] https://github.com/96boards/documentation/raw/master/ConsumerEdition/DragonBoard-410c/HardwareDocs/Schematics_DragonBoard.pdf

Cc: Peter Rosin <peda@axentia.se>
Cc: Peter Chen <peter.chen@nxp.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: <devicetree@vger.kernel.org>
Signed-off-by: Stephen Boyd <stephen.boyd@linaro.org>

---
 Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt |  6 ++++++
 drivers/usb/chipidea/Kconfig                           |  1 +
 drivers/usb/chipidea/core.c                            |  5 +++++
 drivers/usb/chipidea/host.c                            |  7 +++++++
 drivers/usb/chipidea/udc.c                             | 13 ++++++++++++-
 include/linux/usb/chipidea.h                           |  2 ++
 6 files changed, 33 insertions(+), 1 deletion(-)

-- 
2.10.0.297.gf6727b0

Comments

Stephen Boyd July 19, 2017, 1:47 a.m. UTC | #1 
Quoting Peter Chen (2017-07-17 21:41:11)
> On Fri, Jul 14, 2017 at 02:40:04PM -0700, Stephen Boyd wrote:

> >  

> > @@ -175,6 +176,10 @@ static int host_start(struct ci_hdrc *ci)

> >               if (ci_otg_is_fsm_mode(ci)) {

> >                       otg->host = &hcd->self;

> >                       hcd->self.otg_port = 1;

> > +             } else {

> > +                     ret = mux_control_select(ci->platdata->usb_switch, 1);

> 

> It is better to use MACRO for 1 and 0.

> 


Ok.

> > +                     if (ret)

> > +                             goto disable_reg;

> >               }

> >       }

> >  

> > @@ -195,6 +200,8 @@ static void host_stop(struct ci_hdrc *ci)

> >       struct usb_hcd *hcd = ci->hcd;

> >  

> >       if (hcd) {

> > +             if (!ci_otg_is_fsm_mode(ci))

> > +                     mux_control_deselect(ci->platdata->usb_switch);

> >               if (ci->platdata->notify_event)

> >                       ci->platdata->notify_event(ci,

> >                               CI_HDRC_CONTROLLER_STOPPED_EVENT);

> > diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c

> > index d68b125796f9..deb18099e168 100644

> > --- a/drivers/usb/chipidea/udc.c

> > +++ b/drivers/usb/chipidea/udc.c

> > @@ -22,6 +22,7 @@

> >  #include <linux/usb/gadget.h>

> >  #include <linux/usb/otg-fsm.h>

> >  #include <linux/usb/chipidea.h>

> > +#include <linux/mux/consumer.h>

> >  

> >  #include "ci.h"

> >  #include "udc.h"

> > @@ -1964,16 +1965,26 @@ void ci_hdrc_gadget_destroy(struct ci_hdrc *ci)

> >  

> >  static int udc_id_switch_for_device(struct ci_hdrc *ci)

> >  {

> > +     int ret = 0;

> > +

> >       if (ci->is_otg)

> >               /* Clear and enable BSV irq */

> >               hw_write_otgsc(ci, OTGSC_BSVIS | OTGSC_BSVIE,

> >                                       OTGSC_BSVIS | OTGSC_BSVIE);

> >  

> > -     return 0;

> > +     if (!ci_otg_is_fsm_mode(ci))

> > +             ret = mux_control_select(ci->platdata->usb_switch, 0);

> > +

> > +     if (ci->is_otg && ret)

> > +             hw_write_otgsc(ci, OTGSC_BSVIE | OTGSC_BSVIS, OTGSC_BSVIS);

> 

> Should use !ret?

> 


No? This is intended to unwind the clearing and enabling of the BSV irq
on failure (ret is non-zero) and so we clear and disable the BSV irq.
Peter Chen July 19, 2017, 2:05 a.m. UTC | #2 
On Tue, Jul 18, 2017 at 06:47:02PM -0700, Stephen Boyd wrote:
> Quoting Peter Chen (2017-07-17 21:41:11)

> > On Fri, Jul 14, 2017 at 02:40:04PM -0700, Stephen Boyd wrote:

> > >  

> > > @@ -175,6 +176,10 @@ static int host_start(struct ci_hdrc *ci)

> > >               if (ci_otg_is_fsm_mode(ci)) {

> > >                       otg->host = &hcd->self;

> > >                       hcd->self.otg_port = 1;

> > > +             } else {

> > > +                     ret = mux_control_select(ci->platdata->usb_switch, 1);

> > 

> > It is better to use MACRO for 1 and 0.

> > 

> 

> Ok.

> 

> > > +                     if (ret)

> > > +                             goto disable_reg;

> > >               }

> > >       }

> > >  

> > > @@ -195,6 +200,8 @@ static void host_stop(struct ci_hdrc *ci)

> > >       struct usb_hcd *hcd = ci->hcd;

> > >  

> > >       if (hcd) {

> > > +             if (!ci_otg_is_fsm_mode(ci))

> > > +                     mux_control_deselect(ci->platdata->usb_switch);

> > >               if (ci->platdata->notify_event)

> > >                       ci->platdata->notify_event(ci,

> > >                               CI_HDRC_CONTROLLER_STOPPED_EVENT);

> > > diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c

> > > index d68b125796f9..deb18099e168 100644

> > > --- a/drivers/usb/chipidea/udc.c

> > > +++ b/drivers/usb/chipidea/udc.c

> > > @@ -22,6 +22,7 @@

> > >  #include <linux/usb/gadget.h>

> > >  #include <linux/usb/otg-fsm.h>

> > >  #include <linux/usb/chipidea.h>

> > > +#include <linux/mux/consumer.h>

> > >  

> > >  #include "ci.h"

> > >  #include "udc.h"

> > > @@ -1964,16 +1965,26 @@ void ci_hdrc_gadget_destroy(struct ci_hdrc *ci)

> > >  

> > >  static int udc_id_switch_for_device(struct ci_hdrc *ci)

> > >  {

> > > +     int ret = 0;

> > > +

> > >       if (ci->is_otg)

> > >               /* Clear and enable BSV irq */

> > >               hw_write_otgsc(ci, OTGSC_BSVIS | OTGSC_BSVIE,

> > >                                       OTGSC_BSVIS | OTGSC_BSVIE);

> > >  

> > > -     return 0;

> > > +     if (!ci_otg_is_fsm_mode(ci))

> > > +             ret = mux_control_select(ci->platdata->usb_switch, 0);

> > > +

> > > +     if (ci->is_otg && ret)

> > > +             hw_write_otgsc(ci, OTGSC_BSVIE | OTGSC_BSVIS, OTGSC_BSVIS);

> > 

> > Should use !ret?

> > 

> 

> No? This is intended to unwind the clearing and enabling of the BSV irq

> on failure (ret is non-zero) and so we clear and disable the BSV irq.


I see now, I did not notice we have already enabled BSV above.

-- 

Best Regards,
Peter Chen
Stephen Boyd Aug. 8, 2017, 1:51 a.m. UTC | #3 
Quoting Peter Rosin (2017-07-31 03:33:22)
> On 2017-07-14 23:40, Stephen Boyd wrote:

> > @@ -1964,16 +1965,26 @@ void ci_hdrc_gadget_destroy(struct ci_hdrc *ci)

> >  

> >  static int udc_id_switch_for_device(struct ci_hdrc *ci)

> >  {

> > +     int ret = 0;

> > +

> >       if (ci->is_otg)

> >               /* Clear and enable BSV irq */

> >               hw_write_otgsc(ci, OTGSC_BSVIS | OTGSC_BSVIE,

> >                                       OTGSC_BSVIS | OTGSC_BSVIE);

> >  

> > -     return 0;

> > +     if (!ci_otg_is_fsm_mode(ci))

> > +             ret = mux_control_select(ci->platdata->usb_switch, 0);

> > +

> > +     if (ci->is_otg && ret)

> > +             hw_write_otgsc(ci, OTGSC_BSVIE | OTGSC_BSVIS, OTGSC_BSVIS);

> > +

> > +     return ret;

> >  }

> >  

> >  static void udc_id_switch_for_host(struct ci_hdrc *ci)

> >  {

> > +     mux_control_deselect(ci->platdata->usb_switch);

> > +

> 

> This looks broken. You conditionally lock the mux and you unconditionally

> unlock it. Quoting the mux_control_deselect doc:

> 

>  * It is required that a single call is made to mux_control_deselect() for

>  * each and every successful call made to either of mux_control_select() or

>  * mux_control_try_select().

> 

> Think of the mux as a semaphore with a max count of one. If you lock it,

> you have to unlock it when you're done. If you didn't lock it, you have

> zero business unlocking it. If you try to lock it but fail, you also have

> no business unlocking it. Just like a semaphore.


Good catch. I've added a if (!ci_otg_is_fsm_mode()) check here.

> 

> Another point: I do not know if udc_id_switch_for_host is *only* called

> when there has been a prior call to udc_id_switch_for_device that

> succeeded or how this works exactly. But this all looks fragile. Using

> mux_control_select and mux_control_deselect *must* be done in pairs.

> If you want a mux to be locked for "a while", such as in this case, you

> have to make sure you stay within the rules. There is no room for half

> measures, or you will likely cause a deadlock when something unexpected

> happens.

> 


Can you elaborate? Is it bad that we keep it "locked" while we're in
host or device mode? It looked like we paired the start/stop ops with
each other so that the mux is properly managed across these ops. My
testing hasn't shown a problem, but maybe there's some corner case
you're thinking of? I'll double check the code.
Stephen Boyd Aug. 11, 2017, 10:26 p.m. UTC | #4 
Quoting Peter Rosin (2017-08-08 05:46:30)
> On 2017-08-08 03:51, Stephen Boyd wrote:

> 

> >                      It looked like we paired the start/stop ops with

> > each other so that the mux is properly managed across these ops.

> 

> Yes, it *looks* ok...

> 

> >                                                                  My

> > testing hasn't shown a problem, but maybe there's some corner case

> > you're thinking of? I'll double check the code.

> 

> ...but since I do not know the usb code, I can't tell. What I worry about

> is the usb core calling udc_id_switch_for_host or udc_id_switch_for_device

> more than once without any call to the other in between. Maybe that is a

> guarantee that the usb core makes? Or maybe it isn't? If e.g. there is a

> third mode (or if one is added in the future), then the calls to

> mux_control_select and mux_control_deselect would not be paired correctly.

> Ok, sure, a third mode probably doesn't exist and will probably not be

> added, but but but...

> 

> Also, what happens if udc_id_switch_for_device fails? Is it certain that

> it will be called again before udc_id_switch_for_host is called, or is

> the failure simply logged? If the latter, you might have a call to

> mux_control_deselect without a preceding (and successful) call to

> mux_control_select. That's fatal.


The only thing that could fail right now is the mux selection, so we
wouldn't get into some sort of situation where that's locked in and
unchangeable. We do rollback the role if it fails to switch, so we also
wouldn't go into a half-way state of being in one role but not actually
switching all the way over to it.

> 

> I have similar worries for host_start/host_stop, but for that case

> host_stop is not allowed to fail, and it seems like a safe bet that

> host_stop will only be called if host_start succeeds. So, I'm not as

> worried there.

> 

> In other words, the question is if the usb core is designed to allow

> this kind of "raw" resource administration in udc_id_switch_for_host and

> udc_id_switch_for_device, or if you need to keep a local record of the

> state so that you do not do double resource acquisition or attempt to

> free resources you don't have?

> 

> I think I would feel better if the muxing for the device mode could

> be done in a start/stop pair of function just like the host mode is

> doing. Again, I don't know the usb code and don't know if such hooks

> exist or not?

> 


The host_start/host_stop functions are assigned to the same struct
ci_role_driver ops that udc_idc_switch_for_{device,host} are for the
gadget role. Really, these things are called from the same place by the
chipidea driver so not much is different between the two files I modify
to make the mux calls. Furthermore, we don't want to do this if we have
HNP or "true" OTG support so I've put it behind the ci_otg_is_fsm_mode()
check to make sure we don't do any muxing stuff based on fsm state
changes. It doesn't really make any sense here anyway because this
device I have doesn't support OTG, just role switching.
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt b/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
index 0e03344e2e8b..2e9318151df7 100644
--- a/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
+++ b/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
@@ -76,6 +76,10 @@  Optional properties:
   needs to make sure it does not send more than 90%
   maximum_periodic_data_per_frame. The use case is multiple transactions, but
   less frame rate.
+- mux-controls: The mux control for toggling host/device output of this
+  controller. It's expected that a mux state of 0 indicates device mode and a
+  mux state of 1 indicates host mode.
+- mux-control-names: Shall be "usb_switch" if mux-controls is specified.
 
 i.mx specific properties
 - fsl,usbmisc: phandler of non-core register device, with one
@@ -102,4 +106,6 @@  Example:
 		rx-burst-size-dword = <0x10>;
 		extcon = <0>, <&usb_id>;
 		phy-clkgate-delay-us = <400>;
+		mux-controls = <&usb_switch>;
+		mux-control-names = "usb_switch";
 	};
diff --git a/drivers/usb/chipidea/Kconfig b/drivers/usb/chipidea/Kconfig
index 51f4157bbecf..3798e0e69d57 100644
--- a/drivers/usb/chipidea/Kconfig
+++ b/drivers/usb/chipidea/Kconfig
@@ -3,6 +3,7 @@  config USB_CHIPIDEA
 	depends on ((USB_EHCI_HCD && USB_GADGET) || (USB_EHCI_HCD && !USB_GADGET) || (!USB_EHCI_HCD && USB_GADGET)) && HAS_DMA
 	select EXTCON
 	select RESET_CONTROLLER
+	select MULTIPLEXER
 	help
 	  Say Y here if your system has a dual role high speed USB
 	  controller based on ChipIdea silicon IP. It supports:
diff --git a/drivers/usb/chipidea/core.c b/drivers/usb/chipidea/core.c
index b17ed3a9a304..d088c262ebb8 100644
--- a/drivers/usb/chipidea/core.c
+++ b/drivers/usb/chipidea/core.c
@@ -64,6 +64,7 @@ 
 #include <linux/of.h>
 #include <linux/regulator/consumer.h>
 #include <linux/usb/ehci_def.h>
+#include <linux/mux/consumer.h>
 
 #include "ci.h"
 #include "udc.h"
@@ -690,6 +691,10 @@  static int ci_get_platdata(struct device *dev,
 	if (of_find_property(dev->of_node, "non-zero-ttctrl-ttha", NULL))
 		platdata->flags |= CI_HDRC_SET_NON_ZERO_TTHA;
 
+	platdata->usb_switch = devm_mux_control_get_optional(dev, "usb_switch");
+	if (IS_ERR(platdata->usb_switch))
+		return PTR_ERR(platdata->usb_switch);
+
 	ext_id = ERR_PTR(-ENODEV);
 	ext_vbus = ERR_PTR(-ENODEV);
 	if (of_property_read_bool(dev->of_node, "extcon")) {
diff --git a/drivers/usb/chipidea/host.c b/drivers/usb/chipidea/host.c
index 18cb8e46262d..9ef3ecf27ad3 100644
--- a/drivers/usb/chipidea/host.c
+++ b/drivers/usb/chipidea/host.c
@@ -25,6 +25,7 @@ 
 #include <linux/usb/hcd.h>
 #include <linux/usb/chipidea.h>
 #include <linux/regulator/consumer.h>
+#include <linux/mux/consumer.h>
 
 #include "../host/ehci.h"
 
@@ -175,6 +176,10 @@  static int host_start(struct ci_hdrc *ci)
 		if (ci_otg_is_fsm_mode(ci)) {
 			otg->host = &hcd->self;
 			hcd->self.otg_port = 1;
+		} else {
+			ret = mux_control_select(ci->platdata->usb_switch, 1);
+			if (ret)
+				goto disable_reg;
 		}
 	}
 
@@ -195,6 +200,8 @@  static void host_stop(struct ci_hdrc *ci)
 	struct usb_hcd *hcd = ci->hcd;
 
 	if (hcd) {
+		if (!ci_otg_is_fsm_mode(ci))
+			mux_control_deselect(ci->platdata->usb_switch);
 		if (ci->platdata->notify_event)
 			ci->platdata->notify_event(ci,
 				CI_HDRC_CONTROLLER_STOPPED_EVENT);
diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
index d68b125796f9..deb18099e168 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -22,6 +22,7 @@ 
 #include <linux/usb/gadget.h>
 #include <linux/usb/otg-fsm.h>
 #include <linux/usb/chipidea.h>
+#include <linux/mux/consumer.h>
 
 #include "ci.h"
 #include "udc.h"
@@ -1964,16 +1965,26 @@  void ci_hdrc_gadget_destroy(struct ci_hdrc *ci)
 
 static int udc_id_switch_for_device(struct ci_hdrc *ci)
 {
+	int ret = 0;
+
 	if (ci->is_otg)
 		/* Clear and enable BSV irq */
 		hw_write_otgsc(ci, OTGSC_BSVIS | OTGSC_BSVIE,
 					OTGSC_BSVIS | OTGSC_BSVIE);
 
-	return 0;
+	if (!ci_otg_is_fsm_mode(ci))
+		ret = mux_control_select(ci->platdata->usb_switch, 0);
+
+	if (ci->is_otg && ret)
+		hw_write_otgsc(ci, OTGSC_BSVIE | OTGSC_BSVIS, OTGSC_BSVIS);
+
+	return ret;
 }
 
 static void udc_id_switch_for_host(struct ci_hdrc *ci)
 {
+	mux_control_deselect(ci->platdata->usb_switch);
+
 	/*
 	 * host doesn't care B_SESSION_VALID event
 	 * so clear and disbale BSV irq
diff --git a/include/linux/usb/chipidea.h b/include/linux/usb/chipidea.h
index c5fdfcf99828..3b27e333de1d 100644
--- a/include/linux/usb/chipidea.h
+++ b/include/linux/usb/chipidea.h
@@ -9,6 +9,7 @@ 
 #include <linux/usb/otg.h>
 
 struct ci_hdrc;
+struct mux_control;
 
 /**
  * struct ci_hdrc_cable - structure for external connector cable state tracking
@@ -74,6 +75,7 @@  struct ci_hdrc_platform_data {
 	/* VBUS and ID signal state tracking, using extcon framework */
 	struct ci_hdrc_cable		vbus_extcon;
 	struct ci_hdrc_cable		id_extcon;
+	struct mux_control		*usb_switch;
 	u32			phy_clkgate_delay_us;
 };