Message-ID: <278cc2b5-9f0d-840e-372a-7949b79e858d@codeaurora.org>
Date:   Wed, 18 Aug 2021 14:24:29 -0700
From:   Wesley Cheng <wcheng@...eaurora.org>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Felipe Balbi <balbi@...nel.org>
Cc:     "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/Felipe,

On 8/16/2021 12:13 PM, Wesley Cheng wrote:
> Hi Thinh,
> 
> On 8/15/2021 5:33 PM, Thinh Nguyen wrote:
>> Felipe Balbi wrote:
>>>
>>> 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
>>
>> No, resource_index for ep0out is 0, ep0in is 1. You can check from any
>> of the driver tracepoint log for the return value of Start Transfer
>> command for the resource index of ep0. There could be a mixed up with
>> the undocumented return value of Set Endpoint Transfer Resource command
>> before when this code was written, don't mix up with that.
>>
>>> triggered. If you have access to a Lecroy USB Trainer, could you script
>>> this very scenario for verification?
>>
>> For anyone who wants to work on this, we don't need a LeCroy USB
>> trainer. If you use xhci host, just modify the xhci-ring.c to queue a
>> wrong direction DATA phase TRB of a particular control write request
>> test, and continue with the next control requests.
>>
> Let me give this a try since I already have a modified (broken :)) XHCI
> stack.
> 
> Thanks
> Wesley Cheng

Sorry for the late response.  I was trying to get a reliable change to
get the issue to reproduce.  I think I was able to find a set up which
will generate the unexpected direction issue.  I'll try my best to
summarize the traces here:

Set up:
- Modified XHCI stack to queue an IN TRB for a three stage CONTROL OUT
transaction (OUT data stage)
- Device is using RNDIS, as that has interface specific commands (ie
SEND_ENCAPSUALTED messages)

Kernel Log:
[ 1255.312870] msm-usb-hsphy 88e3000.hsphy: Avail curr from USB = 900
[ 1255.315300] dwc3_ep0_xfernotready event status = 1
[ 1255.315429] dwc3_ep0_xfernotready event status = 2
[ 1255.316390] android_work: sent uevent USB_STATE=CONFIGURED
[ 1255.317467] dwc3_ep0_xfernotready event status = 1
[ 1255.317588] dwc3_ep0_xfernotready event status = 2
[ 1255.334196] dwc3_ep0_xfernotready event status = 1
[ 1255.334217] dwc3 a600000.dwc3: unexpected direction for Data Phase
[ 1255.334311] rndis_msg_parser: unknown RNDIS message 0x0052033A len
4456526
[ 1255.334328] RNDIS command error -524, 0/24
[ 1255.334369] ------------[ cut here ]------------
[ 1255.334377] dwc3 a600000.dwc3: No resource for ep0out
[ 1255.334440] WARNING: CPU: 0 PID: 8364 at
drivers/usb/dwc3/gadget.c:360 dwc3_send_gadget_ep_cmd+0x3c4/0x96c
...
 1255.336163] WARNING: CPU: 0 PID: 8364 at drivers/usb/dwc3/ep0.c:281
dwc3_ep0_out_start+0x108/0x144

So the kernel log does indeed show the concern mentioned by Thinh, where
after ending the transfer, we do see the dwc3_ep0_out_start() fail due
to no xfer resource.

ftrace:
<...>-8364    [000] d..1  1255.333988: dwc3_ctrl_req: Get Interface
Status(Intf = 0, Length = 24)
<...>-8364    [000] d..1  1255.334115: dwc3_prepare_trb: ep0out: trb
ffffffc01bffd000 (E1:D0) buf 00000000efb76000 size 24 ctrl 00000455
(HlCs:Sc:data)
<...>-8364    [000] d..1  1255.334128: dwc3_prepare_trb: ep0out: trb
ffffffc01bffd010 (E1:D0) buf 00000000efff9000 size 488 ctrl 00000c53
(HLcs:SC:data)
<...>-8364    [000] d..1  1255.334166: dwc3_gadget_ep_cmd: ep0out: cmd
'Start Transfer' [406] params 00000000 efffa000 00000000 --> status:
Successful
<...>-8364    [000] d..1  1255.334239: dwc3_gadget_ep_cmd: ep0out: cmd
'Set Stall' [404] params 00000000 00000000 00000000 --> status: Successful
<...>-8364    [000] d..1  1255.334291: dwc3_gadget_giveback: ep0out: req
ffffff8891724e00 length 0/24 zsI ==> -104
<...>-8364    [000] d..1  1255.334339: dwc3_prepare_trb: ep0out: trb
ffffffc01bffd010 (E1:D0) buf 00000000efffa000 size 8 ctrl 00000c23
(HLcs:SC:setup)
<...>-8364    [000] d..1  1255.336099: dwc3_gadget_ep_cmd: ep0out: cmd
'Start Transfer' [406] params 00000000 efffa000 00000000 --> status: No
Resource
<...>-8364    [000] d..1  1255.357594: dwc3_ctrl_req: 00 60 b7 ef 00 00
00 00
<...>-8364    [000] d..1  1255.357680: dwc3_gadget_ep_cmd: ep0out: cmd
'Set Stall' [404] params 00000000 00000000 00000000 --> status: Successful
<...>-8364    [000] d..1  1255.357696: dwc3_prepare_trb: ep0out: trb
ffffffc01bffd010 (E1:D0) buf 00000000efffa000 size 8 ctrl 00000c23
(HLcs:SC:setup)
<...>-8364    [000] d..1  1255.357722: dwc3_gadget_ep_cmd: ep0out: cmd
'Start Transfer' [406] params 00000000 efffa000 00000000 --> status:
Successful
<...>-224     [005] d..1  1266.313014: dwc3_gadget_ep_cmd: ep2out: cmd
'End Transfer' [40c08] params 00000000 00000000 00000000 --> status:
Timed Out

Thanks
Wesley Cheng

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