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

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

On 7/13/2022, Wesley Cheng wrote:
> Hi Thinh,
>
> On 7/13/2022 5:19 PM, Thinh Nguyen wrote:
>> On 7/13/2022, Wesley Cheng wrote:
>>> Hi Thinh,
>>>
>>> On 7/12/2022 6:42 PM, Thinh Nguyen wrote:
>>>> On 7/12/2022, Wesley Cheng wrote:
>>>>> Hi Thinh,
>>>>>
>>>>> On 7/8/2022 6:58 PM, Thinh Nguyen wrote:
>>>>>> On 7/8/2022, 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.
>>>>>>>
>>>>>>> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
>>>>>>> ---
>>>>>>>      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;
>>>>>>> -        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 bd40608b19df..fba2797ad9ae 100644
>>>>>>> --- a/drivers/usb/dwc3/gadget.c
>>>>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>>>>> @@ -3696,8 +3696,10 @@ 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;
>>>>>>> +
>>>>>>>          if (!(dep->flags & DWC3_EP_TRANSFER_STARTED) ||
>>>>>>> -        (dep->flags & DWC3_EP_DELAY_STOP) ||
>>>>>>>              (dep->flags & DWC3_EP_END_TRANSFER_PENDING))
>>>>>>>              return;
>>>>>>>      @@ -3744,6 +3746,7 @@ void dwc3_stop_active_transfer(struct
>>>>>>> dwc3_ep *dep, bool force,
>>>>>>>          __dwc3_stop_active_transfer(dep, force, interrupt);
>>>>>>>          spin_lock(&dwc->lock);
>>>>>>>      +    dep->flags &= ~DWC3_EP_DELAY_STOP;
>>>>>>
>>>>>> Can we clear this flag in __dwc3_stop_active_transfer(). It should
>>>>>> apply
>>>>>> if End Transfer command was sent.
>>>>>
>>>>> I wanted to make sure that we weren't modifying the DEP flags outside
>>>>> of a spin lock.  Patch#3 modifies it where we unlock before calling
>>>>> __dwc3_stop_active_transfer(), so we can allow the dwc3 threaded IRQ
>>>>> handle events while the cmd status polling happens.
>>>>>
>>>>> Maybe we can unlock/lock the dwc3->lock inside
>>>>> __dwc3_stop_active_transfer() and that way we can ensure DEP flags 
>>>>> are
>>>>> modified properly?
>>>>
>>>> I didn't realize that you unlock/lock when calling
>>>> __dwc3_stop_active_transfer(). We'd need to be careful if we want to
>>>> unlock/lock it, and avoid it all together if possible. It can be 
>>>> easily
>>>> overlooked just like dwc3_gadget_giveback().
>>>>
>>>> What issue did you see without doing this?
>>>
>>> I saw endxfer timeout issues if I didn't do it.  If we keep the lock
>>> held, then the DWC3 event processing would be blocked across the
>>> entire time we are waiting for the command act to clear.  With
>>> unlocking before polling, then at least we're still able to handle the
>>> EP0 events that are pending.
>>>
>>> It was definitely one of the harder scenarios to reproduce. The main
>>> patch series which resolved a lot of the issues early on was patch#1.
>>> After adding that the other issues are seen maybe after a day or so of
>>> testing.
>>>
>>
>> I see. The soft-disconnect still go through right?
>> Can you try this and see if this works for you?
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 13e4f1a03417..4f67a484c490 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -451,7 +451,9 @@ int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep,
>> unsigned int cmd,
>>
>>           dwc3_writel(dep->regs, DWC3_DEPCMD, cmd);
>>
>> -       if (!(cmd & DWC3_DEPCMD_CMDACT)) {
>> +       if (!(cmd & DWC3_DEPCMD_CMDACT) ||
>> +           (DWC3_DEPCMD_CMD(cmd) == DWC3_DEPCMD_ENDTRANSFER &&
>> +            !(cmd & DWC3_DEPCMD_CMDIOC))) {
>>                   ret = 0;
>>                   goto skip_status;
>>           }
>>
>>
>> We can set it and forget it when we're about to de-initialize the
>> controller. Just like what we've already done by not waiting for the End
>> Transfer endpoint command completion interrupt.
>>
>
> I can see this working for the soft disconnect case, but we'll need to 
> address it differently for the EP dequeue scenario where IOC/interrupt 
> is required to clean up the TRBs.  This is one of the reasons why I 
> went with the spinlock approach, since it would apply to both situations.

I thought we already handled the case for ep dequeue from the last fix. 
Was that not addressed?

Thanks,
Thinh