linux-kernel - Re: [PATCH v2] usb: dwc3: Prevent indefinite sleep in _dwc3_set

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Date:   Tue, 10 Apr 2018 06:29:20 +0000
From:   Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>,
        Roger Quadros <rogerq@...com>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb: dwc3: Prevent indefinite sleep in
 _dwc3_set_mode during suspend/resume

Hi Filipe,

On 3/19/2018 5:53 PM, Minas Harutyunyan wrote:
> Hi,
> 
> On 3/19/2018 3:36 PM, Minas Harutyunyan wrote:
>> Hi,
>>
>> On 3/19/2018 12:55 PM, Felipe Balbi wrote:
>>>
>>> Hi,
>>>
>>> Minas Harutyunyan <Minas.Harutyunyan@...opsys.com> writes:
>>>>>>>>> Thanks for picking this for -next.
>>>>>>>>> Is it better to have this in v4.16-rc fixes?
>>>>>>>>> and also stable? v4.12+
>>>>>>>>
>>>>>>>> Well, there was no "Fixes: foobar" or "Cc: stable" lines in the commit
>>>>>>>> log ;-)
>>>>>>>>
>>>>>>>> The best we can do now, is wait for -rc1 and manually send the commit to
>>>>>>>> stable.
>>>>>>>>
>>>>>>>
>>>>>>> That's fine. Thanks.
>>>>>>>
>>>>>>
>>>>>> Same issue seen in dwc3_gadget_ep_dequeue() function where also used
>>>>>> wait_event_lock_irq() - as result infinite loop.
>>>>>
>>>>> how did this happen? During rmmod dwc3? Or, perhaps, after you unloaded
>>>>> a gadget driver?
>>>>>
>>>> No, not during rmmod's.
>>>> We using our internal USB testing tool. Test case; ISOC OUT, transfer
>>>> size N frames. When host starts ISOC OUT traffic then the dwc3 based on
>>>> "Transfer not ready" event in frame F starts transfers staring from
>>>> frame F+4 (for bInterval=1) as result 4 requests, which already queued
>>>> on device side, remain incomplete. Function driver on some timeout
>>>> trying dequeue these 4 requests (without disabling EP) to complete test.
>>>> For IN ISOC's these requests completed on MISSED ISOC event, but for
>>>> ISOC OUT required call dequeue on some timeout.
>>>
>>> okay
>>>
>>>>>> Actually to fix this issue I updated condition of wait function
>>>>>> from:
>>>>>> !(dep->flags & DWC3_EP_END_TRANSFER_PENDING)
>>>>>> to:
>>>>>> !(dep->flags & DWC3_EP_END_TRANSFER_PENDING & DWC3_EP_ENABLED)
>>>>>
>>>>> you're not fixing anything. You're, essentially, removing the entire
>>>>> end transfer pending logic.
>>>> yes, you are right, but how to overcome this infinite loop? Replace
>>>> wait_event_lock_irq() by  wait_event_interruptible_lock_irq_timeout()?
>>>
>>> The best way here would be to figure why we're missing command complete
>>> IRQ in those cases. According to documentation, we *should* receive that
>>> interrupt, so why is it missing?
>>>
>>
>> Additional info on test. Core configuration is HS only mode, test speed
>> HS, core version v2.90a. Maybe it will help to understand cause of issue.
>> BTW, currently to pass above describe ISOC OUT test we just commented
>> wait_event_lock_irq() in dwc3_gadget_ep_dequeue() function and
>> successfully received request completion in function driver.
>> Thanks,
>> Minas
>>
> 
> One more info: while function driver call dequeue, host periodically
> send control read command to get status of test from function - test In
> Progress or Finished.
> Thanks,
> Minas
> 

Your last dwc3 patch series allow us to successfully dequeuing remaining 
requests without falling in to infinite loop.

Thank you,
Minas