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

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Date:   Fri, 09 Mar 2018 12:36:58 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Roger Quadros <rogerq@...com>, Baolin Wang <baolin.wang@...aro.org>
Cc:     USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: Prevent indefinite sleep in _dwc3_set_mode during suspend/resume


Hi,

Roger Quadros <rogerq@...com> writes:
>>> This is what the v3.10 databook says
>>>
>>> "When issuing an End Transfer command, software must set the CmdIOC
>>> bit (field 8) so that an Endpoint Command Complete event is generated
>>> after the transfer ends. This is necessary to synchronize the
>>> conclusion of system bus traffic before the End Transfer command is
>>> completed."
>>>
>>> with a note
>>>
>>> "If GUCTL2[Rst_actbitlater] is set, Software can poll the completion
>>> of the End Transfer command by polling the command active bit to be
>>> cleared to 0."
>>>
>>> fyi.
>>>
>>> Rst_actbitlater - "Enable clearing of the command active bit for the
>>> ENDXFER command after the command execution is completed.  This bit is
>>> valid in device mode only."
>>>
>>> So I'd prefer not to clear CMDIOC for all cases.
>>>
>>> Could we some how just tackle the dwc3_gadget_exit case like I did in
>>> this patch?
>> 
>> if you can send a version that doesn't iterate over all endpoints twice,
>> sure. We still need a comment somewhere, and I fear we may get
>> interrupts later in some cases. How would we deal with that?
>> 
>
> how about explicitly masking that interrupt? Is it possible?

I think I showed that the bit is reserved on recent dwc3 core releases
(anytyhing 2.40a+, at least).

-- 
balbi

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