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

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Date:   Tue, 12 Jul 2022 15:08:49 -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 4/5] usb: dwc3: Allow end transfer commands to be sent
 during soft disconnect

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@...cinc.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?

Thanks
Wesley Cheng