[PATCH] usb: dwc2: drd: fix clock gating on USB role switch

[PATCH] usb: dwc2: drd: fix clock gating on USB role switch

[Tomas Marek]

The dwc2_handle_usb_suspend_intr() function disables gadget clocks in USB
peripheral mode when no other power-down mode is available (introduced by
commit 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")).
However, the dwc2_drd_role_sw_set() USB role update handler attempts to
read DWC2 registers if the USB role has changed while the USB is in suspend
mode (when the clocks are gated). This causes the system to hang.

Release gadget clocks before handling the USB role update.

Fixes: 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")

Signed-off-by: Tomas Marek <tomas.marek@elrest.cz>
---
 drivers/usb/dwc2/drd.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/usb/dwc2/drd.c b/drivers/usb/dwc2/drd.c
index a8605b02115b..ccb33cd1f04b 100644
--- a/drivers/usb/dwc2/drd.c
+++ b/drivers/usb/dwc2/drd.c
@@ -127,6 +127,18 @@ static int dwc2_drd_role_sw_set(struct usb_role_switch *sw, enum usb_role role)
 			role = USB_ROLE_DEVICE;
 	}
 
+#if IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) || \
+	IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)
+	if (dwc2_is_device_mode(hsotg)) {
+		if (hsotg->lx_state == DWC2_L2) {
+			if (hsotg->params.power_down ==
+			    DWC2_POWER_DOWN_PARAM_NONE && hsotg->bus_suspended &&
+			    !hsotg->params.no_clock_gating)
+				dwc2_gadget_exit_clock_gating(hsotg, 0);
+		}
+	}
+#endif
+
 	if (role == USB_ROLE_HOST) {
 		already = dwc2_ovr_avalid(hsotg, true);
 	} else if (role == USB_ROLE_DEVICE) {
-- 
2.25.1

Re: [PATCH] usb: dwc2: drd: fix clock gating on USB role switch

[Greg KH]

On Tue, Sep 03, 2024 at 11:41:56AM +0200, Tomas Marek wrote:
> The dwc2_handle_usb_suspend_intr() function disables gadget clocks in USB
> peripheral mode when no other power-down mode is available (introduced by
> commit 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")).
> However, the dwc2_drd_role_sw_set() USB role update handler attempts to
> read DWC2 registers if the USB role has changed while the USB is in suspend
> mode (when the clocks are gated). This causes the system to hang.
> 
> Release gadget clocks before handling the USB role update.
> 
> Fixes: 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")
> 
> Signed-off-by: Tomas Marek <tomas.marek@elrest.cz>
> ---
>  drivers/usb/dwc2/drd.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/usb/dwc2/drd.c b/drivers/usb/dwc2/drd.c
> index a8605b02115b..ccb33cd1f04b 100644
> --- a/drivers/usb/dwc2/drd.c
> +++ b/drivers/usb/dwc2/drd.c
> @@ -127,6 +127,18 @@ static int dwc2_drd_role_sw_set(struct usb_role_switch *sw, enum usb_role role)
>  			role = USB_ROLE_DEVICE;
>  	}
>  
> +#if IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) || \
> +	IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)
> +	if (dwc2_is_device_mode(hsotg)) {
> +		if (hsotg->lx_state == DWC2_L2) {
> +			if (hsotg->params.power_down ==
> +			    DWC2_POWER_DOWN_PARAM_NONE && hsotg->bus_suspended &&
> +			    !hsotg->params.no_clock_gating)
> +				dwc2_gadget_exit_clock_gating(hsotg, 0);
> +		}
> +	}
> +#endif
> +
>  	if (role == USB_ROLE_HOST) {
>  		already = dwc2_ovr_avalid(hsotg, true);
>  	} else if (role == USB_ROLE_DEVICE) {
> -- 
> 2.25.1
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- You have marked a patch with a "Fixes:" tag for a commit that is in an
  older released kernel, yet you do not have a cc: stable line in the
  signed-off-by area at all, which means that the patch will not be
  applied to any older kernel releases.  To properly fix this, please
  follow the documented rules in the
  Documentation/process/stable-kernel-rules.rst file for how to resolve
  this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH] usb: dwc2: drd: fix clock gating on USB role switch

[Sergey Shtylyov]

On 9/3/24 12:41 PM, Tomas Marek wrote:

> The dwc2_handle_usb_suspend_intr() function disables gadget clocks in USB
> peripheral mode when no other power-down mode is available (introduced by
> commit 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")).
> However, the dwc2_drd_role_sw_set() USB role update handler attempts to
> read DWC2 registers if the USB role has changed while the USB is in suspend
> mode (when the clocks are gated). This causes the system to hang.
> 
> Release gadget clocks before handling the USB role update.
> 
> Fixes: 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")
> 
> Signed-off-by: Tomas Marek <tomas.marek@elrest.cz>
> ---
>  drivers/usb/dwc2/drd.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/usb/dwc2/drd.c b/drivers/usb/dwc2/drd.c
> index a8605b02115b..ccb33cd1f04b 100644
> --- a/drivers/usb/dwc2/drd.c
> +++ b/drivers/usb/dwc2/drd.c
> @@ -127,6 +127,18 @@ static int dwc2_drd_role_sw_set(struct usb_role_switch *sw, enum usb_role role)
>  			role = USB_ROLE_DEVICE;
>  	}
>  
> +#if IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) || \
> +	IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)
> +	if (dwc2_is_device_mode(hsotg)) {

   Why not avoid #ifdef by doing e.g.:

	if ((IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) || \
	     IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE) &&
	     dwc2_is_device_mode(hsotg)) {

> +		if (hsotg->lx_state == DWC2_L2) {
> +			if (hsotg->params.power_down ==
> +			    DWC2_POWER_DOWN_PARAM_NONE && hsotg->bus_suspended &&
> +			    !hsotg->params.no_clock_gating)

   Well, these *if*s are mergeable too... :-)

> +				dwc2_gadget_exit_clock_gating(hsotg, 0);
> +		}
> +	}
> +#endif
> +
[...]

MBR, Sergey

Re: [PATCH] usb: dwc2: drd: fix clock gating on USB role switch

[Tomas Marek]

Hi Sergey,

thank you for your review.

On Tue, Sep 03, 2024 at 04:20:26PM +0300, Sergey Shtylyov wrote:
> On 9/3/24 12:41 PM, Tomas Marek wrote:
> 
> > The dwc2_handle_usb_suspend_intr() function disables gadget clocks in USB
> > peripheral mode when no other power-down mode is available (introduced by
> > commit 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")).
> > However, the dwc2_drd_role_sw_set() USB role update handler attempts to
> > read DWC2 registers if the USB role has changed while the USB is in suspend
> > mode (when the clocks are gated). This causes the system to hang.
> > 
> > Release gadget clocks before handling the USB role update.
> > 
> > Fixes: 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")
> > 
> > Signed-off-by: Tomas Marek <tomas.marek@elrest.cz>
> > ---
> >  drivers/usb/dwc2/drd.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> > 
> > diff --git a/drivers/usb/dwc2/drd.c b/drivers/usb/dwc2/drd.c
> > index a8605b02115b..ccb33cd1f04b 100644
> > --- a/drivers/usb/dwc2/drd.c
> > +++ b/drivers/usb/dwc2/drd.c
> > @@ -127,6 +127,18 @@ static int dwc2_drd_role_sw_set(struct usb_role_switch *sw, enum usb_role role)
> >  			role = USB_ROLE_DEVICE;
> >  	}
> >  
> > +#if IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) || \
> > +	IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)
> > +	if (dwc2_is_device_mode(hsotg)) {
> 
>    Why not avoid #ifdef by doing e.g.:
> 
> 	if ((IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) || \
> 	     IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE) &&
> 	     dwc2_is_device_mode(hsotg)) {
> 
> > +		if (hsotg->lx_state == DWC2_L2) {
> > +			if (hsotg->params.power_down ==
> > +			    DWC2_POWER_DOWN_PARAM_NONE && hsotg->bus_suspended &&
> > +			    !hsotg->params.no_clock_gating)
> 
>    Well, these *if*s are mergeable too... :-)
> 

OK, why not. In the end all conditions could be merged into one if statement like:

	if ((IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) ||
	     IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)) &&
	     dwc2_is_device_mode(hsotg) &&
	     hsotg->lx_state == DWC2_L2 &&
	     hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_NONE &&
	     hsotg->bus_suspended &&
	     !hsotg->params.no_clock_gating)
		dwc2_gadget_exit_clock_gating(hsotg, 0);

I’ll submit a new patch version with this modification.

Best regards

Tomas

> > +				dwc2_gadget_exit_clock_gating(hsotg, 0);
> > +		}
> > +	}
> > +#endif
> > +
> [...]
> 
> MBR, Sergey