linux-kernel - Re: [PATCH 2/2] usb: dwc3: gadget: Ignore EP queue requests during bus reset

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Date:   Fri, 19 Mar 2021 18:07:36 -0700
From:   Wesley Cheng <wcheng@...eaurora.org>
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>
Subject: Re: [PATCH 2/2] usb: dwc3: gadget: Ignore EP queue requests during
 bus reset



On 3/19/2021 5:40 PM, Thinh Nguyen wrote:
> Hi,
> 
> Wesley Cheng wrote:
>> The current dwc3_gadget_reset_interrupt() will stop any active
>> transfers, but only addresses blocking of EP queuing for while we are
>> coming from a disconnected scenario, i.e. after receiving the disconnect
>> event.  If the host decides to issue a bus reset on the device, the
>> connected parameter will still be set to true, allowing for EP queuing
>> to continue while we are disabling the functions.  To avoid this, set the
>> connected flag to false until the stop active transfers is complete.
>>
>> Signed-off-by: Wesley Cheng <wcheng@...eaurora.org>
>> ---
>>  drivers/usb/dwc3/gadget.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 6e14fdc..d5ed0f69 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -3327,6 +3327,15 @@ static void dwc3_gadget_reset_interrupt(struct dwc3 *dwc)
>>  	u32			reg;
>>  
>>  	/*
>> +	 * Ideally, dwc3_reset_gadget() would trigger the function
>> +	 * drivers to stop any active transfers through ep disable.
>> +	 * However, for functions which defer ep disable, such as mass
>> +	 * storage, we will need to rely on the call to stop active
>> +	 * transfers here, and avoid allowing of request queuing.
>> +	 */
>> +	dwc->connected = false;
>> +
>> +	/*
>>  	 * WORKAROUND: DWC3 revisions <1.88a have an issue which
>>  	 * would cause a missing Disconnect Event if there's a
>>  	 * pending Setup Packet in the FIFO.
>>
> 
> This doesn't look right. Did you have rebase issue with your local
> change again?
> 
> BR,
> Thinh
> 
Hi Thinh,

This was rebased on Greg's usb-linus branch, which has commit
f09ddcfcb8c5 ("usb: dwc3: gadget: Prevent EP queuing while stopping
transfers") merged.

commit f09ddcfcb8c5  moved the dwc->connected = true to after we have
finished stop active transfers.  However, this change will also ensure
that the connected flag is set to false to ensure that when we call stop
active transfers, nothing can prepare TRBs.  (previous commit only
addresses the case where we get the reset interrupt when coming from a
disconnected state)

Thanks
Wesley Cheng

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