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

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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.

> 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.

-- 
Baolin.wang
Best Regards
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