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

[Manu Gautam]

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.
>
>> 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.