Message-ID: <875yw7jkz6.fsf@kernel.org>
Date:   Sun, 15 Aug 2021 09:06:00 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc:     Wesley Cheng <wcheng@...eaurora.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jackp@...eauora.org" <jackp@...eauora.org>
Subject: Re: [RFC][PATCH] usb: dwc3: usb: dwc3: Force stop EP0 transfers
 during pullup disable


Hi,

Thinh Nguyen <Thinh.Nguyen@...opsys.com> writes:
>>>>>>>>> If this occurs, then the entire pullup disable routine is skipped and
>>>>>>>>> proper cleanup and halting of the controller does not complete.
>>>>>>>>> Instead of returning an error (which is ignored from the UDC
>>>>>>>>> perspective), do what is mentioned in the comments and force the
>>>>>>>>> transaction to complete and put the ep0state back to the SETUP phase.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Wesley Cheng <wcheng@...eaurora.org>
>>>>>>>>> ---
>>>>>>>>>  drivers/usb/dwc3/ep0.c    | 4 ++--
>>>>>>>>>  drivers/usb/dwc3/gadget.c | 6 +++++-
>>>>>>>>>  drivers/usb/dwc3/gadget.h | 3 +++
>>>>>>>>>  3 files changed, 10 insertions(+), 3 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
>>>>>>>>> index 6587394..abfc42b 100644
>>>>>>>>> --- a/drivers/usb/dwc3/ep0.c
>>>>>>>>> +++ b/drivers/usb/dwc3/ep0.c
>>>>>>>>> @@ -218,7 +218,7 @@ int dwc3_gadget_ep0_queue(struct usb_ep *ep, struct usb_request *request,
>>>>>>>>>  	return ret;
>>>>>>>>>  }
>>>>>>>>>  
>>>>>>>>> -static void dwc3_ep0_stall_and_restart(struct dwc3 *dwc)
>>>>>>>>> +void dwc3_ep0_stall_and_restart(struct dwc3 *dwc)
>>>>>>>>>  {
>>>>>>>>>  	struct dwc3_ep		*dep;
>>>>>>>>>  
>>>>>>>>> @@ -1073,7 +1073,7 @@ void dwc3_ep0_send_delayed_status(struct dwc3 *dwc)
>>>>>>>>>  	__dwc3_ep0_do_control_status(dwc, dwc->eps[direction]);
>>>>>>>>>  }
>>>>>>>>>  
>>>>>>>>> -static void dwc3_ep0_end_control_data(struct dwc3 *dwc, struct dwc3_ep *dep)
>>>>>>>>> +void dwc3_ep0_end_control_data(struct dwc3 *dwc, struct dwc3_ep *dep)
>>>>>>>>>  {
>>>>>>>>>  	struct dwc3_gadget_ep_cmd_params params;
>>>>>>>>>  	u32			cmd;
>>>>>>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>>>>>>>> index 54c5a08..a0e2e4d 100644
>>>>>>>>> --- a/drivers/usb/dwc3/gadget.c
>>>>>>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>>>>>>> @@ -2437,7 +2437,11 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>>>>>>>>>  				msecs_to_jiffies(DWC3_PULL_UP_TIMEOUT));
>>>>>>>>>  		if (ret == 0) {
>>>>>>>>>  			dev_err(dwc->dev, "timed out waiting for SETUP phase\n");
>>>>>>>>> -			return -ETIMEDOUT;
>>>>>>>>> +			spin_lock_irqsave(&dwc->lock, flags);
>>>>>>>>> +			dwc3_ep0_end_control_data(dwc, dwc->eps[0]);
>>>>>>>>> +			dwc3_ep0_end_control_data(dwc, dwc->eps[1]);
>>>>>>>>
>>>>>>>> End transfer command takes time, need to wait for it to complete before
>>>>>>>> issuing Start transfer again. Also, why restart again when it's about to
>>>>>>>> be disconnected.
>>>>>>>
>>>>>>> I can try without restarting it again, and see if that works.  Instead
>>>>>>> of waiting for the command complete event, can we set the ForceRM bit,
>>>>>>> similar to what we do for dwc3_remove_requests()?
>>>>>>>
>>>>>>
>>>>>> ForceRM=1 means that the controller will ignore updating the TRBs
>>>>>> (including not clearing the HWO and remain transfer size). The driver
>>>>>> still needs to wait for the command to complete before issuing Start
>>>>>> Transfer command. Otherwise Start Transfer won't go through. If we know
>>>>>> that we're not going to issue Start Transfer any time soon, then we may
>>>>>> be able to get away with ignoring End Transfer command completion.
>>>>>>
>>>>>
>>>>> I see.  Currently, in the place that we do use
>>>>> dwc3_ep0_end_control_data(), its followed by
>>>>> dwc3_ep0_stall_and_restart() which would execute start transfer.  For
>>>>
>>>> That doesn't look right. You can try to see if it can recover from a
>>>> control write request. Often time we do control read and not write.
>>>> (i.e. try to End Transfer and immediately Start Transfer on the same
>>>> direction control endpoint).
>>>>
>>> OK, I can try, but just to clarify, I was referring to how it was being
>>> done in:
>>>
>>> static void dwc3_ep0_xfernotready(struct dwc3 *dwc,
>>> 		const struct dwc3_event_depevt *event)
>>> {
>>> ...
>>> 		if (dwc->ep0_expect_in != event->endpoint_number) {
>>> 			struct dwc3_ep	*dep = dwc->eps[dwc->ep0_expect_in];
>>>
>>> 			dev_err(dwc->dev, "unexpected direction for Data Phase\n");
>>> 			dwc3_ep0_end_control_data(dwc, dep);
>>> 			dwc3_ep0_stall_and_restart(dwc);
>>> 			return;
>>> 		}
>>>
>
> Looking at this snippet again, it looks wrong. For control write
> unexpected direction, if the driver hasn't setup and started the DATA
> phase yet, then it's fine, but there is a problem if it did.
>
> Since dwc3_ep0_end_control_data() doesn't issue End Transfer command to
> ep0 due to the resource_index check, it doesn't follow the control

IIRC resource_index is always non-zero, so the command should be
triggered. If you have access to a Lecroy USB Trainer, could you script
this very scenario for verification?

> transfer flow model in the programming guide. This may cause
> dwc3_ep0_stall_and_restart() to overwrite the TRBs for the DATA phase
> with SETUP stage. Also, if the ep0 is already started, the driver won't
> issue Start Transfer command again.

> This issue is unlikely to occur unless we see a misbehave host for
> control write request. Regardless, we need to fix this. I may need some

right, it would be a misbehaving host, however databook called it out as
something that _can_ happen. Moreover, I have vague memories of this
being one of the test cases in Lecroy's USB Certification Suite.

> time before I can create a patch and test it. If you or anyone is up to
> take this on, it'd be highly appreciated.

Before we go ahead writing a patch for this, I'd really like to see
traces showing this failure and a minimal reproducer. The reproducer
would probably have to be a script for Lecroy's USB Trainer.

Keep in mind this entire ep0 stack used to pass USBCV on every -rc and
major release (before I lost access to all my USB gear heh).

-- 
balbi

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