Re: [PATCH v2 4/5] usb: dwc3: Allow end transfer commands to be sent during soft disconnect

Wesley Cheng
2022-07-22T00:04:49Z

Hi Thinh,

On 7/21/2022 5:00 PM, Thinh Nguyen wrote:
> On 7/21/2022, Wesley Cheng wrote:
>> Hi Thinh,
>>
>> On 7/21/2022 3:20 PM, Thinh Nguyen wrote:
>>> On 7/21/2022, Wesley Cheng wrote:
>>>> Hi Thinh,
>>>>
>>>> On 7/21/2022 3:08 PM, Thinh Nguyen wrote:
>>>>> Hi Wesley,
>>>>>
>>>>> On 7/12/2022, Wesley Cheng wrote:
>>>>>> If soft disconnect is in progress, allow the endxfer command to be
>>>>>> sent,
>>>>>> without this, there is an issue where the stop active transfer call
>>>>>> (during pullup disable) wouldn't actually issue the endxfer command,
>>>>>> while clearing the DEP flag.
>>>>>>
>>>>>> In addition, if the DWC3_EP_DELAY_STOP flag was set before soft
>>>>>> disconnect
>>>>>> started (i.e. from the dequeue path), ensure that when the EP0
>>>>>> transaction
>>>>>> completes during soft disconnect, to issue the endxfer with the force
>>>>>> parameter set, as it does not expect a command complete event.
>>>>>>
>>>>>> Fixes: e4cf6580ac740 ("usb: dwc3: gadget: Wait for ep0 xfers to
>>>>>> complete during dequeue")
>>>>>> Suggested-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
>>>>>> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
>>>>>> ---
>>>>>> Link:
>>>>>> https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/1a1a5485-790e-79ce-f5a6-1e96d9b49a47@synopsys.com/__;!!A4F2R9G_pg!cXW2TlALYWnXNPg-NoMFUrQ8K1egEZiQizZ5CA1DOM1Gcw4tfOULy-_2eMGvL8pQPte5dScFON-0wxH2eXu8ijEQUbs$
>>>>>>
>>>>>>
>>>>>>     drivers/usb/dwc3/ep0.c    | 3 +--
>>>>>>     drivers/usb/dwc3/gadget.c | 5 ++++-
>>>>>>     2 files changed, 5 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
>>>>>> index 506ef717fdc0..5851b0e9db0a 100644
>>>>>> --- a/drivers/usb/dwc3/ep0.c
>>>>>> +++ b/drivers/usb/dwc3/ep0.c
>>>>>> @@ -290,8 +290,7 @@ void dwc3_ep0_out_start(struct dwc3 *dwc)
>>>>>>             if (!(dwc3_ep->flags & DWC3_EP_DELAY_STOP))
>>>>>>                 continue;
>>>>>>     -        dwc3_ep->flags &= ~DWC3_EP_DELAY_STOP;
>>>>>
>>>>> If we don't clear this flag here,
>>>>>
>>>>
>>>> This is why I added the dwc->connected argument to control the
>>>> "interrupt" argument.
>>>>
>>>>>> - dwc3_stop_active_transfer(dwc3_ep, true, true);
>>>>>> +        dwc3_stop_active_transfer(dwc3_ep, true, dwc->connected);
>>>>>>         }
>>>>>>     }
>>>>>>     diff --git a/drivers/usb/dwc3/gadget.c
>>>>>> b/drivers/usb/dwc3/gadget.c
>>>>>> index ee85b773e3fe..41b7007358de 100644
>>>>>> --- a/drivers/usb/dwc3/gadget.c
>>>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>>>> @@ -1693,6 +1693,7 @@ static int __dwc3_stop_active_transfer(struct
>>>>>> dwc3_ep *dep, bool force, bool int
>>>>>>             dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
>>>>>>         else if (!ret)
>>>>>>             dep->flags |= DWC3_EP_END_TRANSFER_PENDING;
>>>>>> +    dep->flags &= ~DWC3_EP_DELAY_STOP;
>>>>>>            return ret;
>>>>>>     }
>>>>>> @@ -3686,8 +3687,10 @@ void dwc3_stop_active_transfer(struct dwc3_ep
>>>>>> *dep, bool force,
>>>>>>         if (dep->number <= 1 && dwc->ep0state != EP0_DATA_PHASE)
>>>>>>             return;
>>>>>>     +    if (interrupt && (dep->flags & DWC3_EP_DELAY_STOP))
>>>>>> +        return;
>>>>>> +
>>>>>
>>>>> then it may not go through here. I think I made this same mistake
>>>>> in my
>>>>> previous suggestion.
>>>>>
>>>>
>>>> Since dwc->connected is set to FALSE before we call stop active
>>>> transfers, if we ever run into a situation where delayed stop is set
>>>> already, then it should go through.
>>>>
>>>
>>> Then the check for request dequeue that we did previously will not work
>>> anymore.
>>>
>>
>> Could you help clarify?  The pullup refactor kind of shifted some of
>> the previous checks we had in the dequeue path, and combined with with
>> the stop active transfer checks.
>>
>> I think there was an issue w/ the patch I submitted though.  the above
>> snippet should be replacing what is there:
>>
>> void dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force,
>>     bool interrupt)
>> {
>> ...
>>     if (!(dep->flags & DWC3_EP_TRANSFER_STARTED) ||
>>         /* Following should be removed --- (dep->flags &
>> DWC3_EP_DELAY_STOP) || */
>>         (dep->flags & DWC3_EP_END_TRANSFER_PENDING))
>>         return;
>>
>
> Request dequeue can occur while the device is connected. The
> DWC3_EP_DELAY_STOP intention is to delay sending the End Transfer
> command until the SETUP stage is prepared. If we don't clear the flag
> before the flag check, then the End Transfer command will not go through.
>

Thanks, got it. Understand what you mean now. Let me think about how
to go about it. I probably don't see any issues as of now, because my
test does the soft disconnect, which will do the stop active transfers
forcefully.

Thanks
Wesley Cheng