linux-kernel - Re: [PATCH v2 1/2] usb: dwc3: Not set DWC3_EP_END_TRANSFER

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Date:   Tue, 15 Feb 2022 17:14:50 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Jung Daehwan <dh10.jung@...sung.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>
Subject: Re: [PATCH v2 1/2] usb: dwc3: Not set DWC3_EP_END_TRANSFER_PENDING in
 ep cmd fails

Jung Daehwan wrote:
> Hi Thinh,
> 
> On Mon, Feb 14, 2022 at 06:44:33PM +0000, Thinh Nguyen wrote:
>> Hi,
>>
>> Daehwan Jung wrote:
>>> It always sets DWC3_EP_END_TRANSFER_PENDING in dwc3_stop_active_transfer
>>> even if dwc3_send_gadget_ep_cmd fails. It can cause some problems like
>>
>> How does it fail? Timed out?
> 
> Yes, timed out.
>>
>>> skipping clear stall commmand or giveback from dequeue. We fix to set it
>>> only when ep cmd success. Additionally, We clear DWC3_EP_TRANSFER_STARTED
>>> for next trb to start transfer not update transfer.
>>
>> We shouldn't do this. Things will be out of sync. It may work for 1
>> scenario, but it won't work for others.
>>
>> Please help me understand a few things:
>>
>> 1) What is the scenario that triggers this? Is it random?
>>
> ep cmd timeout occurs on dequeue request from user side. End Transfer command
> would be sent in dwc3_stop_active transfer.

At the high level, what's triggering the request dequeue? Is it from a
disconnect, change of interface, or simply function driver protocol that
changes it.

What application was used to trigger this?

> 
>> 2) Are there other traffics pending while issuing the End Transfer
>> command? If so, what transfer type(s)?
>>
> I haven't checked it yet. 

Can you check?

> 
>> 3) Have you tried increasing the timeout?
>>
> No, I haven't.

Can you try up to 10 seconds (just for experiment)

>> BR,
>> Thinh
>>
> 
> This issue occurs very rarely on customer. I only have restricted
> information. That's why I've been trying to reproduce it.

How did you test your fix if you can't reproduce it?

> 
> Wesley may have run into same issue and you can see this issue in detail.
> https://urldefense.com/v3/__https://protect2.fireeye.com/v1/url?k=9d423b69-fc3fd32e-9d43b026-74fe485fff30-77a099b52659410d&q=1&e=20b4d9f5-2599-4f57-8b6a-7c4ec167d228&u=https*3A*2F*2Flore.kernel.org*2Flinux-usb*2F20220203080017.27339-1-quic_wcheng*40quicinc.com*2F__;JSUlJSUlJQ!!A4F2R9G_pg!JWPzNLoO3BFX_IZCVzmHPtxq6frr_VFbSNNaxSQylunt1Y4EauTOefth2LCIcVEuTx8E$ 
> 

I can take a look, but please provide the tracepoints of the failure if
you can reproduce it.

Thanks,
Thinh