[PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields

[PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields

[John Stultz]

From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>

The current code in dwc3_gadget_ep_reclaim_completed_trb() will
check for IOC/LST bit in the event->status and returns if
IOC/LST bit is set. This logic doesn't work if multiple TRBs
are queued per request and the IOC/LST bit is set on the last
TRB of that request.

Consider an example where a queued request has multiple queued
TRBs and IOC/LST bit is set only for the last TRB. In this case,
the core generates XferComplete/XferInProgress events only for
the last TRB (since IOC/LST are set only for the last TRB). As
per the logic in dwc3_gadget_ep_reclaim_completed_trb()
event->status is checked for IOC/LST bit and returns on the
first TRB. This leaves the remaining TRBs left unhandled.

Similarly, if the gadget function enqueues an unaligned request
with sglist already in it, it should fail the same way, since we
will append another TRB to something that already uses more than
one TRB.

To aviod this, this patch changes the code to check for IOC/LST
bits in TRB->ctrl instead.

At a practical level, this patch resolves USB transfer stalls seen
with adb on dwc3 based HiKey960 after functionfs gadget added
scatter-gather support around v4.20.

Cc: Felipe Balbi <balbi@kernel.org>
Cc: Yang Fei <fei.yang@intel.com>
Cc: Thinh Nguyen <thinhn@synopsys.com>
Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Cc: Jack Pham <jackp@codeaurora.org>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Linux USB List <linux-usb@vger.kernel.org>
Cc: stable <stable@vger.kernel.org>
Tested-by: Tejas Joglekar <tejas.joglekar@synopsys.com>
Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
[jstultz: forward ported to mainline, reworded commit log, reworked
 to only check trb->ctrl as suggested by Felipe]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
v2:
* Rework to only check trb->ctrl as suggested by Felipe
* Reword the commit message to include more of Felipe's assessment
---
 drivers/usb/dwc3/gadget.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 154f3f3e8cff..9a085eee1ae3 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2420,7 +2420,8 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep,
 	if (event->status & DEPEVT_STATUS_SHORT && !chain)
 		return 1;
 
-	if (event->status & DEPEVT_STATUS_IOC)
+	if ((trb->ctrl & DWC3_TRB_CTRL_IOC) ||
+	    (trb->ctrl & DWC3_TRB_CTRL_LST))
 		return 1;
 
 	return 0;
-- 
2.17.1

Re: [PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields

[Felipe Balbi]

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Hi,

John Stultz <john.stultz@linaro.org> writes:

> From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
>
> The current code in dwc3_gadget_ep_reclaim_completed_trb() will
> check for IOC/LST bit in the event->status and returns if
> IOC/LST bit is set. This logic doesn't work if multiple TRBs
> are queued per request and the IOC/LST bit is set on the last
> TRB of that request.
>
> Consider an example where a queued request has multiple queued
> TRBs and IOC/LST bit is set only for the last TRB. In this case,
> the core generates XferComplete/XferInProgress events only for
> the last TRB (since IOC/LST are set only for the last TRB). As
> per the logic in dwc3_gadget_ep_reclaim_completed_trb()
> event->status is checked for IOC/LST bit and returns on the
> first TRB. This leaves the remaining TRBs left unhandled.
>
> Similarly, if the gadget function enqueues an unaligned request
> with sglist already in it, it should fail the same way, since we
> will append another TRB to something that already uses more than
> one TRB.
>
> To aviod this, this patch changes the code to check for IOC/LST
> bits in TRB->ctrl instead.
>
> At a practical level, this patch resolves USB transfer stalls seen
> with adb on dwc3 based HiKey960 after functionfs gadget added
> scatter-gather support around v4.20.
>
> Cc: Felipe Balbi <balbi@kernel.org>
> Cc: Yang Fei <fei.yang@intel.com>
> Cc: Thinh Nguyen <thinhn@synopsys.com>
> Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
> Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> Cc: Jack Pham <jackp@codeaurora.org>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Greg KH <gregkh@linuxfoundation.org>
> Cc: Linux USB List <linux-usb@vger.kernel.org>
> Cc: stable <stable@vger.kernel.org>
> Tested-by: Tejas Joglekar <tejas.joglekar@synopsys.com>
> Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
> [jstultz: forward ported to mainline, reworded commit log, reworked
>  to only check trb->ctrl as suggested by Felipe]
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v2:
> * Rework to only check trb->ctrl as suggested by Felipe
> * Reword the commit message to include more of Felipe's assessment
> ---
>  drivers/usb/dwc3/gadget.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 154f3f3e8cff..9a085eee1ae3 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2420,7 +2420,8 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep,
>  	if (event->status & DEPEVT_STATUS_SHORT && !chain)
>  		return 1;
>  
> -	if (event->status & DEPEVT_STATUS_IOC)
> +	if ((trb->ctrl & DWC3_TRB_CTRL_IOC) ||
> +	    (trb->ctrl & DWC3_TRB_CTRL_LST))

why the LST bit here? It wasn't there before. In fact, we never set LST
in dwc3 anymore :-)

-- 
balbi

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Re: [PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields

[John Stultz]

On Tue, Jan 28, 2020 at 5:23 AM Felipe Balbi <balbi@kernel.org> wrote:
>
>
> Hi,
>
> John Stultz <john.stultz@linaro.org> writes:
>
> > From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
> >
> > The current code in dwc3_gadget_ep_reclaim_completed_trb() will
> > check for IOC/LST bit in the event->status and returns if
> > IOC/LST bit is set. This logic doesn't work if multiple TRBs
> > are queued per request and the IOC/LST bit is set on the last
> > TRB of that request.
> >
> > Consider an example where a queued request has multiple queued
> > TRBs and IOC/LST bit is set only for the last TRB. In this case,
> > the core generates XferComplete/XferInProgress events only for
> > the last TRB (since IOC/LST are set only for the last TRB). As
> > per the logic in dwc3_gadget_ep_reclaim_completed_trb()
> > event->status is checked for IOC/LST bit and returns on the
> > first TRB. This leaves the remaining TRBs left unhandled.
> >
> > Similarly, if the gadget function enqueues an unaligned request
> > with sglist already in it, it should fail the same way, since we
> > will append another TRB to something that already uses more than
> > one TRB.
> >
> > To aviod this, this patch changes the code to check for IOC/LST
> > bits in TRB->ctrl instead.
> >
> > At a practical level, this patch resolves USB transfer stalls seen
> > with adb on dwc3 based HiKey960 after functionfs gadget added
> > scatter-gather support around v4.20.
> >
> > Cc: Felipe Balbi <balbi@kernel.org>
> > Cc: Yang Fei <fei.yang@intel.com>
> > Cc: Thinh Nguyen <thinhn@synopsys.com>
> > Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
> > Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> > Cc: Jack Pham <jackp@codeaurora.org>
> > Cc: Todd Kjos <tkjos@google.com>
> > Cc: Greg KH <gregkh@linuxfoundation.org>
> > Cc: Linux USB List <linux-usb@vger.kernel.org>
> > Cc: stable <stable@vger.kernel.org>
> > Tested-by: Tejas Joglekar <tejas.joglekar@synopsys.com>
> > Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
> > Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
> > [jstultz: forward ported to mainline, reworded commit log, reworked
> >  to only check trb->ctrl as suggested by Felipe]
> > Signed-off-by: John Stultz <john.stultz@linaro.org>
> > ---
> > v2:
> > * Rework to only check trb->ctrl as suggested by Felipe
> > * Reword the commit message to include more of Felipe's assessment
> > ---
> >  drivers/usb/dwc3/gadget.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > index 154f3f3e8cff..9a085eee1ae3 100644
> > --- a/drivers/usb/dwc3/gadget.c
> > +++ b/drivers/usb/dwc3/gadget.c
> > @@ -2420,7 +2420,8 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep,
> >       if (event->status & DEPEVT_STATUS_SHORT && !chain)
> >               return 1;
> >
> > -     if (event->status & DEPEVT_STATUS_IOC)
> > +     if ((trb->ctrl & DWC3_TRB_CTRL_IOC) ||
> > +         (trb->ctrl & DWC3_TRB_CTRL_LST))
>
> why the LST bit here? It wasn't there before. In fact, we never set LST
> in dwc3 anymore :-)

So, it was in the patch before, just on separate lines:
  https://lore.kernel.org/lkml/20200122222645.38805-2-john.stultz@linaro.org/

- if (event->status & DEPEVT_STATUS_IOC)
+ if ((event->status & DEPEVT_STATUS_IOC) &&
+    (trb->ctrl & DWC3_TRB_CTRL_IOC))
+ return 1;
+
+ if ((event->status & DEPEVT_STATUS_LST) &&
+    (trb->ctrl & DWC3_TRB_CTRL_LST))
  return 1;

So I just merged the two checks into one line. But I'm ok to drop the
CTRL_LST check if that really isn't used.  Let me know and I'll rework
and resend.

thanks
-john

Re: [PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields

[Thinh Nguyen]

Hi,

Felipe Balbi wrote:
> Hi,
>
> John Stultz <john.stultz@linaro.org> writes:
>
>> From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
>>
>> The current code in dwc3_gadget_ep_reclaim_completed_trb() will
>> check for IOC/LST bit in the event->status and returns if
>> IOC/LST bit is set. This logic doesn't work if multiple TRBs
>> are queued per request and the IOC/LST bit is set on the last
>> TRB of that request.
>>
>> Consider an example where a queued request has multiple queued
>> TRBs and IOC/LST bit is set only for the last TRB. In this case,
>> the core generates XferComplete/XferInProgress events only for
>> the last TRB (since IOC/LST are set only for the last TRB). As
>> per the logic in dwc3_gadget_ep_reclaim_completed_trb()
>> event->status is checked for IOC/LST bit and returns on the
>> first TRB. This leaves the remaining TRBs left unhandled.
>>
>> Similarly, if the gadget function enqueues an unaligned request
>> with sglist already in it, it should fail the same way, since we
>> will append another TRB to something that already uses more than
>> one TRB.
>>
>> To aviod this, this patch changes the code to check for IOC/LST
>> bits in TRB->ctrl instead.
>>
>> At a practical level, this patch resolves USB transfer stalls seen
>> with adb on dwc3 based HiKey960 after functionfs gadget added
>> scatter-gather support around v4.20.
>>
>> Cc: Felipe Balbi <balbi@kernel.org>
>> Cc: Yang Fei <fei.yang@intel.com>
>> Cc: Thinh Nguyen <thinhn@synopsys.com>
>> Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
>> Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
>> Cc: Jack Pham <jackp@codeaurora.org>
>> Cc: Todd Kjos <tkjos@google.com>
>> Cc: Greg KH <gregkh@linuxfoundation.org>
>> Cc: Linux USB List <linux-usb@vger.kernel.org>
>> Cc: stable <stable@vger.kernel.org>
>> Tested-by: Tejas Joglekar <tejas.joglekar@synopsys.com>
>> Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
>> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
>> [jstultz: forward ported to mainline, reworded commit log, reworked
>>   to only check trb->ctrl as suggested by Felipe]
>> Signed-off-by: John Stultz <john.stultz@linaro.org>
>> ---
>> v2:
>> * Rework to only check trb->ctrl as suggested by Felipe
>> * Reword the commit message to include more of Felipe's assessment
>> ---
>>   drivers/usb/dwc3/gadget.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 154f3f3e8cff..9a085eee1ae3 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2420,7 +2420,8 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep,
>>   	if (event->status & DEPEVT_STATUS_SHORT && !chain)
>>   		return 1;
>>   
>> -	if (event->status & DEPEVT_STATUS_IOC)
>> +	if ((trb->ctrl & DWC3_TRB_CTRL_IOC) ||
>> +	    (trb->ctrl & DWC3_TRB_CTRL_LST))
> why the LST bit here? It wasn't there before. In fact, we never set LST
> in dwc3 anymore :-)
>

Just a note: right now, it may be fine for non-stream endpoints to not 
set the LST bit in the TRBs. For streams, we need to set this bit so the 
controller know to allocate resource for different transfers of 
different streams. It may be fine now if you think that it should be 
added later when more fixes for streams are added, but I think it 
doesn't hurt checking it now either.

BR,
Thinh

Re: [PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields

[Felipe Balbi]

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Hi,

Thinh Nguyen <Thinh.Nguyen@synopsys.com> writes:
>> John Stultz <john.stultz@linaro.org> writes:
>>
>>> From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
>>>
>>> The current code in dwc3_gadget_ep_reclaim_completed_trb() will
>>> check for IOC/LST bit in the event->status and returns if
>>> IOC/LST bit is set. This logic doesn't work if multiple TRBs
>>> are queued per request and the IOC/LST bit is set on the last
>>> TRB of that request.
>>>
>>> Consider an example where a queued request has multiple queued
>>> TRBs and IOC/LST bit is set only for the last TRB. In this case,
>>> the core generates XferComplete/XferInProgress events only for
>>> the last TRB (since IOC/LST are set only for the last TRB). As
>>> per the logic in dwc3_gadget_ep_reclaim_completed_trb()
>>> event->status is checked for IOC/LST bit and returns on the
>>> first TRB. This leaves the remaining TRBs left unhandled.
>>>
>>> Similarly, if the gadget function enqueues an unaligned request
>>> with sglist already in it, it should fail the same way, since we
>>> will append another TRB to something that already uses more than
>>> one TRB.
>>>
>>> To aviod this, this patch changes the code to check for IOC/LST
>>> bits in TRB->ctrl instead.
>>>
>>> At a practical level, this patch resolves USB transfer stalls seen
>>> with adb on dwc3 based HiKey960 after functionfs gadget added
>>> scatter-gather support around v4.20.
>>>
>>> Cc: Felipe Balbi <balbi@kernel.org>
>>> Cc: Yang Fei <fei.yang@intel.com>
>>> Cc: Thinh Nguyen <thinhn@synopsys.com>
>>> Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
>>> Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
>>> Cc: Jack Pham <jackp@codeaurora.org>
>>> Cc: Todd Kjos <tkjos@google.com>
>>> Cc: Greg KH <gregkh@linuxfoundation.org>
>>> Cc: Linux USB List <linux-usb@vger.kernel.org>
>>> Cc: stable <stable@vger.kernel.org>
>>> Tested-by: Tejas Joglekar <tejas.joglekar@synopsys.com>
>>> Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
>>> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
>>> [jstultz: forward ported to mainline, reworded commit log, reworked
>>>   to only check trb->ctrl as suggested by Felipe]
>>> Signed-off-by: John Stultz <john.stultz@linaro.org>
>>> ---
>>> v2:
>>> * Rework to only check trb->ctrl as suggested by Felipe
>>> * Reword the commit message to include more of Felipe's assessment
>>> ---
>>>   drivers/usb/dwc3/gadget.c | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>> index 154f3f3e8cff..9a085eee1ae3 100644
>>> --- a/drivers/usb/dwc3/gadget.c
>>> +++ b/drivers/usb/dwc3/gadget.c
>>> @@ -2420,7 +2420,8 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep,
>>>   	if (event->status & DEPEVT_STATUS_SHORT && !chain)
>>>   		return 1;
>>>   
>>> -	if (event->status & DEPEVT_STATUS_IOC)
>>> +	if ((trb->ctrl & DWC3_TRB_CTRL_IOC) ||
>>> +	    (trb->ctrl & DWC3_TRB_CTRL_LST))
>> why the LST bit here? It wasn't there before. In fact, we never set LST
>> in dwc3 anymore :-)
>
> Just a note: right now, it may be fine for non-stream endpoints to not 
> set the LST bit in the TRBs. For streams, we need to set this bit so the 
> controller know to allocate resource for different transfers of 
> different streams. It may be fine now if you think that it should be 
> added later when more fixes for streams are added, but I think it 
> doesn't hurt checking it now either.

Indeed. Let's keep this version as is if we will need LST for Streams
anyway. Sorry for the noise.

-- 
balbi

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Re: [PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields

[Felipe Balbi]

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Hi,

John Stultz <john.stultz@linaro.org> writes:
> From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
>
> The current code in dwc3_gadget_ep_reclaim_completed_trb() will
> check for IOC/LST bit in the event->status and returns if
> IOC/LST bit is set. This logic doesn't work if multiple TRBs
> are queued per request and the IOC/LST bit is set on the last
> TRB of that request.
>
> Consider an example where a queued request has multiple queued
> TRBs and IOC/LST bit is set only for the last TRB. In this case,
> the core generates XferComplete/XferInProgress events only for
> the last TRB (since IOC/LST are set only for the last TRB). As
> per the logic in dwc3_gadget_ep_reclaim_completed_trb()
> event->status is checked for IOC/LST bit and returns on the
> first TRB. This leaves the remaining TRBs left unhandled.
>
> Similarly, if the gadget function enqueues an unaligned request
> with sglist already in it, it should fail the same way, since we
> will append another TRB to something that already uses more than
> one TRB.
>
> To aviod this, this patch changes the code to check for IOC/LST
> bits in TRB->ctrl instead.
>
> At a practical level, this patch resolves USB transfer stalls seen
> with adb on dwc3 based HiKey960 after functionfs gadget added
> scatter-gather support around v4.20.
>
> Cc: Felipe Balbi <balbi@kernel.org>
> Cc: Yang Fei <fei.yang@intel.com>
> Cc: Thinh Nguyen <thinhn@synopsys.com>
> Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
> Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> Cc: Jack Pham <jackp@codeaurora.org>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Greg KH <gregkh@linuxfoundation.org>
> Cc: Linux USB List <linux-usb@vger.kernel.org>
> Cc: stable <stable@vger.kernel.org>
> Tested-by: Tejas Joglekar <tejas.joglekar@synopsys.com>
> Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
> [jstultz: forward ported to mainline, reworded commit log, reworked
>  to only check trb->ctrl as suggested by Felipe]
> Signed-off-by: John Stultz <john.stultz@linaro.org>

since v5.5 is already merged, I'll send this to Greg once -rc1 is
tagged. It's already in my testing/fixes branch waiting for a pull
request.

cheers

-- 
balbi

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Re: [PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields

[John Stultz]

On Tue, Jan 28, 2020 at 11:23 PM Felipe Balbi <balbi@kernel.org> wrote:
> John Stultz <john.stultz@linaro.org> writes:
> > From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
> >
> > The current code in dwc3_gadget_ep_reclaim_completed_trb() will
> > check for IOC/LST bit in the event->status and returns if
> > IOC/LST bit is set. This logic doesn't work if multiple TRBs
> > are queued per request and the IOC/LST bit is set on the last
> > TRB of that request.
> >
> > Consider an example where a queued request has multiple queued
> > TRBs and IOC/LST bit is set only for the last TRB. In this case,
> > the core generates XferComplete/XferInProgress events only for
> > the last TRB (since IOC/LST are set only for the last TRB). As
> > per the logic in dwc3_gadget_ep_reclaim_completed_trb()
> > event->status is checked for IOC/LST bit and returns on the
> > first TRB. This leaves the remaining TRBs left unhandled.
> >
> > Similarly, if the gadget function enqueues an unaligned request
> > with sglist already in it, it should fail the same way, since we
> > will append another TRB to something that already uses more than
> > one TRB.
> >
> > To aviod this, this patch changes the code to check for IOC/LST
> > bits in TRB->ctrl instead.
> >
> > At a practical level, this patch resolves USB transfer stalls seen
> > with adb on dwc3 based HiKey960 after functionfs gadget added
> > scatter-gather support around v4.20.
> >
> > Cc: Felipe Balbi <balbi@kernel.org>
> > Cc: Yang Fei <fei.yang@intel.com>
> > Cc: Thinh Nguyen <thinhn@synopsys.com>
> > Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
> > Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> > Cc: Jack Pham <jackp@codeaurora.org>
> > Cc: Todd Kjos <tkjos@google.com>
> > Cc: Greg KH <gregkh@linuxfoundation.org>
> > Cc: Linux USB List <linux-usb@vger.kernel.org>
> > Cc: stable <stable@vger.kernel.org>
> > Tested-by: Tejas Joglekar <tejas.joglekar@synopsys.com>
> > Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
> > Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
> > [jstultz: forward ported to mainline, reworded commit log, reworked
> >  to only check trb->ctrl as suggested by Felipe]
> > Signed-off-by: John Stultz <john.stultz@linaro.org>
>
> since v5.5 is already merged, I'll send this to Greg once -rc1 is
> tagged. It's already in my testing/fixes branch waiting for a pull
> request.

Great, thanks so much for queueing this! I'll be digging on the db845c
side wrt the dma-api issue to hopefully get that one sorted as well.

Thanks again for the help and analysis!
-john

Re: [PATCH v2] usb: dwc3: gadget: Check for IOC/LST bit in TRB->ctrl fields

[Felipe Balbi]

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Hi,

John Stultz <john.stultz@linaro.org> writes:
> On Tue, Jan 28, 2020 at 11:23 PM Felipe Balbi <balbi@kernel.org> wrote:
>> John Stultz <john.stultz@linaro.org> writes:
>> > From: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
>> >
>> > The current code in dwc3_gadget_ep_reclaim_completed_trb() will
>> > check for IOC/LST bit in the event->status and returns if
>> > IOC/LST bit is set. This logic doesn't work if multiple TRBs
>> > are queued per request and the IOC/LST bit is set on the last
>> > TRB of that request.
>> >
>> > Consider an example where a queued request has multiple queued
>> > TRBs and IOC/LST bit is set only for the last TRB. In this case,
>> > the core generates XferComplete/XferInProgress events only for
>> > the last TRB (since IOC/LST are set only for the last TRB). As
>> > per the logic in dwc3_gadget_ep_reclaim_completed_trb()
>> > event->status is checked for IOC/LST bit and returns on the
>> > first TRB. This leaves the remaining TRBs left unhandled.
>> >
>> > Similarly, if the gadget function enqueues an unaligned request
>> > with sglist already in it, it should fail the same way, since we
>> > will append another TRB to something that already uses more than
>> > one TRB.
>> >
>> > To aviod this, this patch changes the code to check for IOC/LST
>> > bits in TRB->ctrl instead.
>> >
>> > At a practical level, this patch resolves USB transfer stalls seen
>> > with adb on dwc3 based HiKey960 after functionfs gadget added
>> > scatter-gather support around v4.20.
>> >
>> > Cc: Felipe Balbi <balbi@kernel.org>
>> > Cc: Yang Fei <fei.yang@intel.com>
>> > Cc: Thinh Nguyen <thinhn@synopsys.com>
>> > Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
>> > Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
>> > Cc: Jack Pham <jackp@codeaurora.org>
>> > Cc: Todd Kjos <tkjos@google.com>
>> > Cc: Greg KH <gregkh@linuxfoundation.org>
>> > Cc: Linux USB List <linux-usb@vger.kernel.org>
>> > Cc: stable <stable@vger.kernel.org>
>> > Tested-by: Tejas Joglekar <tejas.joglekar@synopsys.com>
>> > Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
>> > Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
>> > [jstultz: forward ported to mainline, reworded commit log, reworked
>> >  to only check trb->ctrl as suggested by Felipe]
>> > Signed-off-by: John Stultz <john.stultz@linaro.org>
>>
>> since v5.5 is already merged, I'll send this to Greg once -rc1 is
>> tagged. It's already in my testing/fixes branch waiting for a pull
>> request.
>
> Great, thanks so much for queueing this! I'll be digging on the db845c

no worries, it was way past the time :-)

> side wrt the dma-api issue to hopefully get that one sorted as well.

Thanks, that would, indeed, be great :-)

> Thanks again for the help and analysis!

no worries. If you find anything odd, just collect traces and I can help
have a look.

-- 
balbi

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