[PATCH 0/2] Fix allowing of ep queuing while stopping transfers

[PATCH 0/2] Fix allowing of ep queuing while stopping transfers

[Wesley Cheng]

commit f09ddcfcb8c5 ("usb: dwc3: gadget: Prevent EP queuing while stopping
transfers") addressed an issue where the DWC3 gadget was still allowing EP
queuing to occur while the pullup disable routine was executing.  This led to
a situation where the controller prepares a TRB, which will be unmapped by the
stop active transfer call.

In addition to the above, there are a few other places in the DWC3 gadget where
we need to block preparing of TRBs:

 1. While the DWC3 gadget cleans up completed TRBs (during
    dwc3_gadget_endpoint_trbs_complete()), DWC3 gadget giveback is utilized and
    will release the dwc->lock.  If a pullup disable call occurs while the
    cleanup is happening, then there is a chance dwc3_gadget_ep_should_continue
    will prepare a TRB, which will later on be unmapped by the stop active
    transfer in the pullup disable path.

 2. If we are in the CONFIGURED state and the host issues a bus RESET.  In this
    situation, the connected flag is still set to true while we stop active
    transfers, which can lead to the same initial problem.  Ideally, function
    drivers would stop any pending usb requests through dwc3_reset_gadget()
    using the EP disable call, but for some function drivers, this does not
    occur synchronously in their disable() callback.  These functions would rely
    on the stop active transfers in the reset handler to issue the endxfer cmd.

Wesley Cheng (2):
  usb: dwc3: gadget: Avoid continuing preparing TRBs during teardown
  usb: dwc3: gadget: Ignore EP queue requests during bus reset

 drivers/usb/dwc3/gadget.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH 1/2] usb: dwc3: gadget: Avoid continuing preparing TRBs during teardown

[Wesley Cheng]

Add checks similar to dwc3_gadget_ep_queue() before kicking off
transfers after getting an endpoint completion event.   Since cleaning
up completed requests will momentarily unlock dwc->lock, there is a
chance for a sequence like pullup disable to be executed.  This can
lead to preparing a TRB, which will be removed by the pullup disable
routine.

Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
---
 drivers/usb/dwc3/gadget.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 4a337f3..6e14fdc 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2912,6 +2912,11 @@ static void dwc3_gadget_ep_cleanup_completed_requests(struct dwc3_ep *dep,
 static bool dwc3_gadget_ep_should_continue(struct dwc3_ep *dep)
 {
 	struct dwc3_request	*req;
+	struct dwc3		*dwc = dep->dwc;
+
+	if (!dep->endpoint.desc || !dwc->pullups_connected ||
+	    !dwc->connected)
+		return false;
 
 	if (!list_empty(&dep->pending_list))
 		return true;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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

[Wesley Cheng]

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@codeaurora.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.
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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

[Thinh Nguyen]

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@codeaurora.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

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

[Wesley Cheng]

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@codeaurora.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

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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

[Thinh Nguyen]

Wesley Cheng wrote:
> 
> 
> 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@codeaurora.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.

Ah I see.

> 
> 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)
> 

That still doesn't address this issue.

Because:
1) We're still protected by the spin_lock_irq*(), so this change doesn't
make any difference while handling an event.
2) We don't enable the interrupt for END_TRANSFER command completion
when doing dwc3_stop_active_transfers(), the
DWC3_EP_END_TRANSFER_PENDING flag will not be set to prevent preparing
new requests.

We should do dwc->connected = true when we handle connection_done
interrupt instead. The END_TRANSFER command should complete before this.

Thanks,
Thinh

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

[Thinh Nguyen]

Thinh Nguyen wrote:
> Wesley Cheng wrote:
>>
>>
>> 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@codeaurora.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.
> 
> Ah I see.
> 
>>
>> 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)
>>
> 
> That still doesn't address this issue.
> 
> Because:
> 1) We're still protected by the spin_lock_irq*(), so this change doesn't
> make any difference while handling an event.
> 2) We don't enable the interrupt for END_TRANSFER command completion
> when doing dwc3_stop_active_transfers(), the
> DWC3_EP_END_TRANSFER_PENDING flag will not be set to prevent preparing
> new requests.
> 
> We should do dwc->connected = true when we handle connection_done
> interrupt instead. The END_TRANSFER command should complete before this.
> 
> Thanks,
> Thinh
> 

Just want to clarify, I was referring to your previous commit
f09ddcfcb8c5, we'd still need dwc->connected = false when handling reset
interrupt as you've done here.

BR,
Thinh

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

[Wesley Cheng]

Hi Thinh,


On 3/19/2021 7:01 PM, Thinh Nguyen wrote:
> Wesley Cheng wrote:
>>
>>
>> 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@codeaurora.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.
> 
> Ah I see.
> 
>>
>> 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)
>>
> 
> That still doesn't address this issue.
> 
> Because:
> 1) We're still protected by the spin_lock_irq*(), so this change doesn't
> make any difference while handling an event.

Thank you for the feedback.  So it is true that we lock dwc->lock while
handling EP/device events, but what these changes are trying to address
is that during dwc3_stop_active_transfers() we will eventually call
dwc3_gadget_giveback() to call the complete() functions registered by
the function driver.  Before we call the complete() callbacks, we unlock
dwc->lock, so we are no longer protected, and if there was a pending ep
queue from a function driver, that would allow it to acquire the lock
and continue preparing the TRBs.

> 2) We don't enable the interrupt for END_TRANSFER command completion
> when doing dwc3_stop_active_transfers(), the
> DWC3_EP_END_TRANSFER_PENDING flag will not be set to prevent preparing
> new requests.
> 
Agreed.  That is the reason for adding the check to dwc->connected in
__dwc3_gadget_ep_queue()

if (!dep->endpoint.desc || !dwc->pullups_connected || !dwc->connected) {
 		dev_err(dwc->dev, "%s: can't queue to disabled endpoint\n",
 				dep->name);
 		return -ESHUTDOWN;

> We should do dwc->connected = true when we handle connection_done
> interrupt instead. The END_TRANSFER command should complete before this.
> 
So how this change will address the issue is:

1.  IRQ handler will acquire dwc->lock
2.  dwc3_gadget_reset_handler() sets dwc->connected = false
3.  Call to dwc3_stop_active_transfers()
	---> dwc3_gadget_giveback() releases dwc->lock
4.  If there was a pending ep queue (waiting for dwc->lock) it can
continue here
5.  __dwc3_gadget_ep_queue() exits early due to dwc->connected = false
6.  dwc3_gadget_giveback() re-acquires dwc->lock and continues

Thanks
Wesley Cheng

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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

[Thinh Nguyen]

Wesley Cheng wrote:
> Hi Thinh,
> 
> 
> On 3/19/2021 7:01 PM, Thinh Nguyen wrote:
>> Wesley Cheng wrote:
>>>
>>>
>>> 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@codeaurora.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.
>>
>> Ah I see.
>>
>>>
>>> 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)
>>>
>>
>> That still doesn't address this issue.
>>
>> Because:
>> 1) We're still protected by the spin_lock_irq*(), so this change doesn't
>> make any difference while handling an event.
> 
> Thank you for the feedback.  So it is true that we lock dwc->lock while
> handling EP/device events, but what these changes are trying to address
> is that during dwc3_stop_active_transfers() we will eventually call
> dwc3_gadget_giveback() to call the complete() functions registered by
> the function driver.  Before we call the complete() callbacks, we unlock
> dwc->lock, so we are no longer protected, and if there was a pending ep
> queue from a function driver, that would allow it to acquire the lock
> and continue preparing the TRBs.
> 
Ah I forgot about that.


>> 2) We don't enable the interrupt for END_TRANSFER command completion
>> when doing dwc3_stop_active_transfers(), the
>> DWC3_EP_END_TRANSFER_PENDING flag will not be set to prevent preparing
>> new requests.
>>
> Agreed.  That is the reason for adding the check to dwc->connected in
> __dwc3_gadget_ep_queue()
> 
> if (!dep->endpoint.desc || !dwc->pullups_connected || !dwc->connected) {
>  		dev_err(dwc->dev, "%s: can't queue to disabled endpoint\n",
>  				dep->name);
>  		return -ESHUTDOWN;
> 
>> We should do dwc->connected = true when we handle connection_done
>> interrupt instead. The END_TRANSFER command should complete before this.
>>
> So how this change will address the issue is:
> 
> 1.  IRQ handler will acquire dwc->lock
> 2.  dwc3_gadget_reset_handler() sets dwc->connected = false
> 3.  Call to dwc3_stop_active_transfers()
> 	---> dwc3_gadget_giveback() releases dwc->lock
> 4.  If there was a pending ep queue (waiting for dwc->lock) it can
> continue here
> 5.  __dwc3_gadget_ep_queue() exits early due to dwc->connected = false
> 6.  dwc3_gadget_giveback() re-acquires dwc->lock and continues
> 

Ok. I thought this was for different issue. I thought you were trying to
solve an issue where a request is queued immediately after handling the
reset interrupt but before the END_TRANSFER command completion.

Thanks for the clarification.

BR,
Thinh