Re: [PATCH] usb: dwc3: gadget: Avoid runtime resume if disabling pullup

[Wesley Cheng]

On 8/3/2021 12:58 AM, Felipe Balbi wrote:
> 
> Jack Pham <jackp@xxxxxxxxxxxxxx> writes:
> 
>> Hi Wesley,
>>
>> On Fri, Jul 30, 2021 at 05:29:34PM -0700, Wesley Cheng wrote:
>>> If the device is already in the runtime suspended state, any call to
>>> the pullup routine will issue a runtime resume on the DWC3 core
>>> device.  If the USB gadget is disabling the pullup, then avoid having
>>> to issue a runtime resume, as DWC3 gadget has already been
>>> halted/stopped.
>>>
>>> This fixes an issue where the following condition occurs:
>>>
>>> usb_gadget_remove_driver()
>>> -->usb_gadget_disconnect()
>>>  -->dwc3_gadget_pullup(0)
>>>   -->pm_runtime_get_sync() -> ret = 0
>>>   -->pm_runtime_put() [async]
>>> -->usb_gadget_udc_stop()
>>>  -->dwc3_gadget_stop()
>>>   -->dwc->gadget_driver = NULL
>>> ...
>>>
>>> dwc3_suspend_common()
>>> -->dwc3_gadget_suspend()
>>>  -->DWC3 halt/stop routine skipped, driver_data == NULL
>>>
>>> This leads to a situation where the DWC3 gadget is not properly
>>> stopped, as the runtime resume would have re-enabled EP0 and event
>>> interrupts, and since we avoided the DWC3 gadget suspend, these
>>> resources were never disabled.
>>>
>>> Signed-off-by: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>
>>> ---
>>>  drivers/usb/dwc3/gadget.c | 11 +++++++++++
>>>  1 file changed, 11 insertions(+)
>>>
>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>> index a29a4ca..5d08454 100644
>>> --- a/drivers/usb/dwc3/gadget.c
>>> +++ b/drivers/usb/dwc3/gadget.c
>>> @@ -2435,6 +2435,17 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>>>  	}
>>>  
>>>  	/*
>>> +	 * Avoid issuing a runtime resume if the device is already in the
>>> +	 * suspended state during gadget disconnect.  DWC3 gadget was already
>>> +	 * halted/stopped during runtime suspend.
>>> +	 */
>>> +	if (!is_on) {
>>> +		pm_runtime_barrier(dwc->dev);
>>> +		if (pm_runtime_suspended(dwc->dev))
>>> +			return 0;
>>> +	}
>>> +
>>> +	/*
>>>  	 * Check the return value for successful resume, or error.  For a
>>>  	 * successful resume, the DWC3 runtime PM resume routine will handle
>>>  	 * the run stop sequence, so avoid duplicate operations here.

Hi Jack/Felipe,

>>
>> Should this also go to stable with Fixes: 77adb8bdf422 ("usb: dwc3:
>> gadget: Allow runtime suspend if UDC unbinded") ?
> 
> sounds like a good idea.
> 

Sure, will update the commit text with the fixes tag.  Thanks!

Regards,
Wesley Cheng

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project