Re: [PATCH] usb: dwc3: Support the dwc3 host suspend/resume

[Baolin Wang]

Hi,

On 21 July 2017 at 17:13, Manu Gautam <mgautam@xxxxxxxxxxxxxx> wrote:
> Hi,
>
> On 7/21/2017 2:31 PM, Baolin Wang wrote:
>> On 21 July 2017 at 16:45, Manu Gautam <mgautam@xxxxxxxxxxxxxx> wrote:
>>> Hi,
>>>
>>>
>>> On 7/21/2017 12:28 PM, Baolin Wang wrote:
>>>> For some mobile devices with strict power management, we also want to
>>>> suspend the host when the slave was detached for power saving. Thus
>>>> adding the host suspend/resume functions to support this requirement.
>>>
>>> USB/PM core already takes care of suspending root-HUB/XHCI when
>>> no device connected.
>> Correct, but what I mean is we can power off the dwc3 controller when
>> there are no device connected.
>>
>>>> We will issue the pm_suspend_ignore_children() for the dwc3 device,
>>>> since we will resume the child device (xHCI device) in runtime resume
>>>> callback (dwc3_host_resume()) of dwc3 device, now the dwc3 device's
>>>> runtime state is not RPM_ACTIVE, which will block to resume its
>>>> child device (xHCI device). Add ignore children flag can avoid this
>>>> situation.
>>> This defeats the basic purpose of runtime PM. Without ignore_children
>>> once USB bus is suspended, dwc3 gets suspended and then dwc3 glue device.
>>> Only requirement I see from the patch is to resume XHCI/root-hub on
>>> dwc3 resume. I am sure there must be other way to deal with that e.g.
>>> doing same from glue driver by using a wq or use pm_request_resume()
>> Ah, I will try pm_request_resume().
>>
>>>> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
>>>> ---
>>>>  drivers/usb/dwc3/core.c |   26 +++++++++++++++++++++++++-
>>>>  drivers/usb/dwc3/core.h |    7 +++++++
>>>>  drivers/usb/dwc3/host.c |   15 +++++++++++++++
>>>>  3 files changed, 47 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>>>> index 326b302..2be7ddc 100644
>>>> --- a/drivers/usb/dwc3/core.c
>>>> +++ b/drivers/usb/dwc3/core.c
>>>> @@ -1193,6 +1193,7 @@ static int dwc3_probe(struct platform_device *pdev)
>>>>       pm_runtime_use_autosuspend(dev);
>>>>       pm_runtime_set_autosuspend_delay(dev, DWC3_DEFAULT_AUTOSUSPEND_DELAY);
>>>>       pm_runtime_enable(dev);
>>>> +     pm_suspend_ignore_children(dev, true);
>>>>       ret = pm_runtime_get_sync(dev);
>>>>       if (ret < 0)
>>>>               goto err1;
>>>> @@ -1292,15 +1293,27 @@ static int dwc3_remove(struct platform_device *pdev)
>>>>  static int dwc3_suspend_common(struct dwc3 *dwc)
>>> What is the trigger for runtime suspend now that you have ignore_children set.
>>>>  {
>>>>       unsigned long   flags;
>>>> +     int             ret;
>>>>
>>>>       switch (dwc->dr_mode) {
>>>>       case USB_DR_MODE_PERIPHERAL:
>>>> +             spin_lock_irqsave(&dwc->lock, flags);
>>>> +             dwc3_gadget_suspend(dwc);
>>>> +             spin_unlock_irqrestore(&dwc->lock, flags);
>>>> +             break;
>>>>       case USB_DR_MODE_OTG:
>>>> +             ret = dwc3_host_suspend(dwc);
>>> With DRD/OTG, if current mode is device and dwc3->xhci won't be valid.
>> If current mode is device, then xHCI device is always in suspend state.
> dwc->xhci is allocated in dwc3_host_init. And dwc->xhci device is unregistred
> from dwc3_host_exit that is called from __dwc3_set_mode.

Yes, you are right. I think I need check the dwc->current_dr_role to
identify host or device mode.

>>
>>> You can refer to the patch that I pushed to address this.
>>>
>>>> +             if (ret)
>>>> +                     return ret;
>>>> +
>>>>               spin_lock_irqsave(&dwc->lock, flags);
>>>>               dwc3_gadget_suspend(dwc);
>>>>               spin_unlock_irqrestore(&dwc->lock, flags);
>>>>               break;
>>>>       case USB_DR_MODE_HOST:
>>>> +             ret = dwc3_host_suspend(dwc);
>>>> +             if (ret)
>>>> +                     return ret;
>>>>       default:
>>>>               /* do nothing */
>>>>               break;
>>>> @@ -1322,12 +1335,23 @@ static int dwc3_resume_common(struct dwc3 *dwc)
>>>>
>>>>       switch (dwc->dr_mode) {
>>>>       case USB_DR_MODE_PERIPHERAL:
>>>> +             spin_lock_irqsave(&dwc->lock, flags);
>>>> +             dwc3_gadget_resume(dwc);
>>>> +             spin_unlock_irqrestore(&dwc->lock, flags);
>>>> +             break;
>>>>       case USB_DR_MODE_OTG:
>>>> +             ret = dwc3_host_resume(dwc);
>>>> +             if (ret)
>>>> +                     return ret;
>>>> +
>>>>               spin_lock_irqsave(&dwc->lock, flags);
>>>>               dwc3_gadget_resume(dwc);
>>>>               spin_unlock_irqrestore(&dwc->lock, flags);
>>>> -             /* FALLTHROUGH */
>>>> +             break;
>>>>       case USB_DR_MODE_HOST:
>>>> +             ret = dwc3_host_resume(dwc);
>>>> +             if (ret)
>>>> +                     return ret;
>>>>       default:
>>>>               /* do nothing */
>>>>               break;
>>>> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
>>>> index ea910ac..9b5a4eb 100644
>>>> --- a/drivers/usb/dwc3/core.h
>>>> +++ b/drivers/usb/dwc3/core.h
>>>> @@ -1193,11 +1193,18 @@ static inline bool dwc3_is_usb31(struct dwc3 *dwc)
>>>>  #if IS_ENABLED(CONFIG_USB_DWC3_HOST) || IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
>>>>  int dwc3_host_init(struct dwc3 *dwc);
>>>>  void dwc3_host_exit(struct dwc3 *dwc);
>>>> +int dwc3_host_suspend(struct dwc3 *dwc);
>>>> +int dwc3_host_resume(struct dwc3 *dwc);
>>>>  #else
>>>>  static inline int dwc3_host_init(struct dwc3 *dwc)
>>>>  { return 0; }
>>>>  static inline void dwc3_host_exit(struct dwc3 *dwc)
>>>>  { }
>>>> +
>>>> +static inline int dwc3_host_suspend(struct dwc3 *dwc)
>>>> +{ return 0; }
>>>> +static inline int dwc3_host_resume(struct dwc3 *dwc)
>>>> +{ return 0; }
>>>>  #endif
>>>>
>>>>  #if IS_ENABLED(CONFIG_USB_DWC3_GADGET) || IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
>>>> diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
>>>> index 76f0b0d..3fa4414 100644
>>>> --- a/drivers/usb/dwc3/host.c
>>>> +++ b/drivers/usb/dwc3/host.c
>>>> @@ -16,6 +16,7 @@
>>>>   */
>>>>
>>>>  #include <linux/platform_device.h>
>>>> +#include <linux/pm_runtime.h>
>>>>
>>>>  #include "core.h"
>>>>
>>>> @@ -151,3 +152,17 @@ void dwc3_host_exit(struct dwc3 *dwc)
>>>>                         dev_name(dwc->dev));
>>>>       platform_device_unregister(dwc->xhci);
>>>>  }
>>>> +
>>>> +int dwc3_host_suspend(struct dwc3 *dwc)
>>>> +{
>>>> +     struct device *xhci = &dwc->xhci->dev;
>>>> +
>>>> +     return pm_runtime_suspend(xhci);
>>> If ignore_children is not marked then xhci would indeed be suspended.
>>>
>>>> +}
>>>> +
>>>> +int dwc3_host_resume(struct dwc3 *dwc)
>>>> +{
>>>> +     struct device *xhci = &dwc->xhci->dev;
>>>> +
>>>> +     return pm_runtime_resume(xhci);
>>> Other than what I pushed in my patch -
>>> ("usb: dwc3: Don't reinitialize core during host bus-suspend/resume")
>>> Just performing pm_request_resume or handling same in dwc3 glue
>>> driver should be sufficient.
>> Yes.
>>
>>> Also, what is trigger for runtime_resume for your platform?
>> In our platform glue layer, we have extcon events to notify there are
>> devices connected, then gule layer will resume dwc3 device.
>>
>
> IMO you can just perform resume of &dwc->xhci->dev instead of resuming dwc3.
> Since, dwc3 is parent of xhci that will trigger resume of dwc3 as well.

I am not sure this is good enough but it seems can solve some
problems, then we do not need resume/suspend host in dwc3 core.

-- 
Baolin.wang
Best Regards