Re: [PATCH v2] usb: dwc3: gadget: Wait for end transfer complete before free irq

From: Felipe Balbi
Date: Thu Oct 13 2016 - 03:54:40 EST


Baolin Wang <> writes:
> Hi,
> On 13 October 2016 at 15:02, Felipe Balbi <balbi@xxxxxxxxxx> wrote:
>> Hi,
>> Baolin Wang <> writes:
>>> @@ -1742,6 +1791,17 @@ static int dwc3_gadget_stop(struct usb_gadget *g)
>>> dwc->gadget_driver = NULL;
>>> spin_unlock_irqrestore(&dwc->lock, flags);
>>> + /*
>>> + * Since the xHCI will share the same interrupt with gadget, thus when
>>> + * free the gadget irq, it will not shutdown this gadget irq line. Then
>>> + * the gadget driver can not handle the end transfer command complete
>>> + * event after free the gadget irq, which will hang the system to crash.
>>> + *
>>> + * So we should wait for the end transfer command complete event before
>>> + * free it to avoid this situation.
>>> + */
>>> + dwc3_wait_command_complete(dwc);
>> this doesn't make sense. We have already masked all interrupts before
>> getting here. We have also, already, disabled all endpoints.
> No, you just mask the interrupts described in DEVTEN register, and you
> did not disable the endpoint command complete event.

True that

>> I'm thinking this is a bug in configfs interface of Gadget API, not
>> dwc3. The only reason for this to happen would be if we get to
>> ->udc_stop() with endpoints still enabled.
>> Can you check if that's the case? i.e. can you check if any endpoints
>> are still enabled when we get here?
> No, it is not any endpoints are still enabled. Like I said in commit
> message, we will start end transfer command when disable the endpoint,
> if the end transfer command complete event comes after we have freed
> the gadget irq, it will trigger the interrupt line all the time to
> crash the system.

I see what the problem is. Databook tells us we *must* set CMDIOC when
issuing EndTransfer command and we should always wait for Command
Complete IRQ. However, we took a shortcut and just delayed for 100us
after issuing End Transfer.

It seems as if *that* should be fixed. We should start actually waiting
for Command Complete IRQ.


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