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

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Message-ID: <87vawwtpdp.fsf@linux.intel.com>
Date:   Thu, 13 Oct 2016 15:17:06 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Baolin Wang <baolin.wang@...aro.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


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.

-- 
balbi

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