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

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Date:   Mon, 19 Mar 2018 10:54:34 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>,
        Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>,
        Roger Quadros <rogerq@...com>
Cc:     "linux-usb\@vger.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb: dwc3: Prevent indefinite sleep in _dwc3_set_mode during suspend/resume


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?

-- 
balbi

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