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

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Date:   Fri, 9 Mar 2018 11:26:41 +0200
From:   Roger Quadros <rogerq@...com>
To:     Felipe Balbi <balbi@...nel.org>,
        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

On 09/03/18 11:23, Felipe Balbi wrote:
> 
> Hi,
> 
> Roger Quadros <rogerq@...com> writes:
> 
> <snip>
> 
>>>> When we set up the DWC3_DEPCMD_ENDTRANSFER command in
>>>> dwc3_stop_active_transfer(), we can do not set DWC3_DEPCMD_CMDIOC,
>>>> then there will no endpoint command complete interrupts I think.
>>>>
>>>> cmd |= DWC3_DEPCMD_CMDIOC;
>>>
>>> I remember some part of the databook mandating CMDIOC to be set. We
>>> could test it out without and see if anything blows up. I would,
>>> however, require a lengthy comment explaining that we're deviating from
>>> databook revision x.yya, section foobar because $reasons. :-)
>>>
>>
>> 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?

-- 
cheers,
-roger

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