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

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Date:   Thu, 21 Jul 2022 15:40:06 -0700
From:   Wesley Cheng <quic_wcheng@...cinc.com>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>
Subject: Re: [PATCH v2 4/5] usb: dwc3: Allow end transfer commands to be sent
 during soft disconnect

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@...opsys.com>
>>>> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.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;

Thanks
Wesley Cheng