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 19:46:03 +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

Hi Felipe,

On 13 October 2016 at 19:22, Felipe Balbi <balbi@...nel.org> wrote:
>
> Hi,
>
> Janusz Dziedzic <janusz.dziedzic@...to.com> writes:
>>>> Baolin Wang <baolin.wang@...aro.org> writes:
>>>>>>>>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>>>>>>>>>> index 1783406..ca2ae5b 100644
>>>>>>>>>>> --- a/drivers/usb/dwc3/gadget.c
>>>>>>>>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>>>>>>>>> @@ -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.

> you're sending me. I just reviewed this part of the code and we _do_
> indeed enable the control pipe before connecting pullups and that *must*
> be done this way, otherwise we won't be able to receive first Setup
> packet from host.
>
> How have you tested this? Against which tree?
>
> --
> balbi



-- 
Baolin.wang
Best Regards