linux-kernel - Re: [RESEND PATCH v3 1/2] usb: dwc3: gadget: Add disconnect checking when changing function dynamically

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Date:   Thu, 13 Oct 2016 20:23:23 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     Janusz Dziedzic <janusz.dziedzic@...to.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Mark Brown <broonie@...nel.org>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND PATCH v3 1/2] usb: dwc3: gadget: Add disconnect checking
 when changing function dynamically

On 13 October 2016 at 20:17, Felipe Balbi <balbi@...nel.org> wrote:
>
> Hi,
>
> Baolin Wang <baolin.wang@...aro.org> writes:
>>>>>>>>>>>>> @@ -241,6 +241,9 @@ int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned cmd,
>>>>>>>>>>>>>       int                     susphy = false;
>>>>>>>>>>>>>       int                     ret = -EINVAL;
>>>>>>>>>>>>>
>>>>>>>>>>>>> +     if (!dwc->pullups_connected)
>>>>>>>>>>>>> +             return -ESHUTDOWN;
>>>>>>>>>>>>> +
>>>>>>>>>>
>>>>>>>>>> you skip trace_dwc3_gadget_ep_cmd()
>>>>>>>>>
>>>>>>>>> Yes, we did not need trace here since we did not send out the command.
>>>>>>>>>
>>>>>>>> What in such case: enumeration will not work and this will be because
>>>>>>>> this ESHUTDOWN or wrong pullups_connected usage. Without a trace you
>>>>>>>> will not know where the problem is.
>>>>>>>> In my opinion this trace could be useful.
>>>>>>>
>>>>>>> We have returned the '-ESHUTDOWN' error number for user to know what
>>>>>>> happened.
>>>>>>
>>>>>> No, this is actually not good and Janusz has a very valid point
>>>>>> here. When we're debugging something in dwc3, we want to rely on
>>>>>> tracepoints to tell us what's going on. I don't want to have to add more
>>>>>> debugging messages to print out that ESHUTDOWN error just so I can
>>>>>> figure out what's going on. You should be patching this in a way that
>>>>>> the tracepoint is still printed out properly.
>>>>>
>>>>> Fine. Will fix this in next version.
>>>>>
>>>>
>>>> BTW, did you test this patch with device mode?
>>>> Seems in my setup this fail - DWC3_DEPCMD_SETEPCONFIG for ep0out and
>>>> gadget_start() failed (enumeration fail).
>>>> Don't we need to queue ep0 cmds before pullup?
>>>
>>> Baolin, it's clear to me that you're not testing any of the patches
>>
>> I am sure I tested every patch I send to you. But this one is really
>> my mistake and I thought this is just one small change with just eye
>> review. I am really sorry for troubles.
>
> fair enough, luckily Janusz caught it before any harm could be
> done. Thanks for taking the time to explain.

Thanks for understanding and thanks for Janusz's testing.


-- 
Baolin.wang
Best Regards