Re: [PATCH v2 1/2] usb: dwc3: Not set DWC3_EP_END_TRANSFER_PENDING in ep cmd fails

[Wesley Cheng]

Hi Thinh,

On 2/28/2022 7:02 PM, Thinh Nguyen wrote:
> Wesley Cheng wrote:
>> Hi Thinh,
>>
>> On 2/28/2022 5:09 PM, Thinh Nguyen wrote:
>>> Hi Wesley,
>>>
> 
> <snip>
> 
>>>
>>> [ 2181.481956865       0x9dc63f265]   dbg_complete: ep6in: trb ffffffc01e7f52a0 (E43:D43) buf 00000000ebaf0000 size 1x 0 ctrl 00000810 (hlcs:sC:normal)
>>> [ 2181.482044730       0x9dc63f8fc]   dbg_gadget_giveback: ep6in: req ffffff8860657500 length 8/8 zsI ==> 0
>>> [ 2181.482222490       0x9dc640651]   event (0000c040): ep0out: Transfer Complete (sIL) [Setup Phase]
>>> [ 2181.482273271       0x9dc640a20]   dbg_trace_log_ctrl: Get Interface Status(Intf = 4, Length = 20)
>>> [ 2181.482334782       0x9dc640ebc]   dbg_ep_queue: ep6in: req ffffff8860657500 length 0/8 zsI ==> -115
>>> [ 2181.482357386       0x9dc64106e]   dbg_prepare: ep6in: trb ffffffc01e7f52b0 (E44:D43) buf 00000000ea578000 size 1x 8 ctrl 00000811 (Hlcs:sC:normal)
>>> [ 2181.482391865       0x9dc641304]   dbg_send_ep_cmd: ep6in: cmd 'Update Transfer' [d0007] params 00000000 00000000 00000000 --> status: Successful
>>> [ 2181.482485615       0x9dc641a0d]   dbg_send_ep_cmd: ep0out: cmd 'Start Transfer' [406] params 00000000 efffa000 00000000 --> status: Successful
>>> [ 2181.482565303       0x9dc642006]   event (000010c0): ep0out: Transfer Not Ready [0] (Not Active) [Data Phase]
>>> [ 2181.482719417       0x9dc642b96]   event (00002040): ep0out: Transfer Complete (Sil) [Data Phase]
>>> [ 2181.482814938       0x9dc6432c0]   dbg_gadget_giveback: ep0out: req ffffff87df84d900 length 20/20 zsI ==> 0
>>> [ 2181.482926084       0x9dc643b16]   event (000020c2): ep0in: Transfer Not Ready [0] (Not Active) [Status Phase]
>>> [ 2181.483024261       0x9dc644272]   dbg_send_ep_cmd: ep0in: cmd 'Start Transfer' [406] params 00000000 efffa000 00000000 --> status: Successful
>>>
>>> The control status isn't completed here.
>>>
>>> [ 2181.483069521       0x9dc6445d7]   dbg_ep_dequeue: ep2in: req ffffff879f5a8b00 length 0/63680 zsI ==> -115
>>> [ 2181.496068792       0x9dc6814c9]   dbg_send_ep_cmd: ep2in: cmd 'End Transfer' [50d08] params 00000000 00000000 00000000 --> status: Timed Out
>>>
>>> But the dequeue may come when host already sent a new Setup packet.
>>> The ep0out hasn't started yet at the point.
>>>
>>> Due to various system latency, I can see that this can happen when
>>> the dwc3 driver hasn't received the interrupt notified the status stage
>>> event yet.
>>>
>>> If that's the case, the host may have already sent the Setup packet
>>> at this point. So the End Transfer may get stuck if the Setup packet
>>> isn't DMA out yet.
>>>
>>> Can you try the change below to see if it resolves the issue?
>> Thanks, Thinh.  Sure I'll give it a try with this change.  This is very
>> similar to the change proposed here as well:
>>
>> https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/20220216000835.25400-3-quic_wcheng@xxxxxxxxxxx/__;!!A4F2R9G_pg!KlgSpNELOXQydIQuarA3A4NJXIcvHslXqzOdBwYqUIR97Mqdp8zdyezhOC9EJ6UqxLxM$ 
>>
> 
> Not sure if this completely resolves the issue here. The change seems to
> issue the End Transfer command before Start Transfer for the next Setup
> stage completes. Also it's missing some checks for async calls to the
> endpoint that's pending dequeue. Also, we may not need to wait for End
> Transfer command to time out if we know the condition to avoid.
> 
>> One thing to mention is that, I'm not sure how dependable checking soley
>> the ep0state would be.  I've seen some scenarios where we'd run into the
>> end transfer timeout during the time between inspecting the SETUP packet
>> (dwc3_ep0_inspect_setup()) and when the data phase is queued.  The
>> timing of the data phase can potentially differ if it is a vendor
>> specific control request.
> 
> This timeout should only apply to Setup packet and Setup stage. Even if
> it's vendor specific control request, it should be fine. Host should not
> issue a Setup packet until it receives a status stage (unless there's a
> disconnect in the middle of a control transfer, but that's a different
> issue).
> 
> If you do see a problem. We can take a look further.
> 
So far so good w/ the testing.  Had to make a small change in your patch
to fix a typo:
                if (!(dwc3_ep->flags & DWC3_EP_DELAY_STOP))
                        continue;

                dwc3_ep->flags &= ~DWC3_EP_DELAY_STOP;
                ret = dwc3_stop_active_transfer(dwc3_ep, true, true);

Was using dep instead of dwc3_ep.  Will let this run over the weekend
and get back to you.

Thanks
Wesley Cheng

>>
>> This is what led me to try w/ marking the endxfer delay after getting a
>> timed out scenario.  Just something to consider :).  I'll let you know
>> how it goes!  Thanks again.
>>
>> Thanks
>> Wesley Cheng
>>
>>> Code is not tested. Let me know if the logic makes sense. The change is
>>> to delay End Transfer when the Start Transfer for ep0out is completed.
>>>
> 
> Thanks,
> Thinh

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