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From:   Anurag Kumar Vulisha <anuragku@xilinx.com>
To:     Felipe Balbi <balbi@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Shuah Khan <shuah@kernel.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Johan Hovold <johan@kernel.org>,
        Jaejoong Kim <climbbb.kim@gmail.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Roger Quadros <rogerq@ti.com>,
        Manu Gautam <mgautam@codeaurora.org>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        Bart Van Assche <bvanassche@acm.org>,
        Mike Christie <mchristi@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Colin Ian King <colin.king@canonical.com>
CC:     "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "v.anuragkumar@gmail.com" <v.anuragkumar@gmail.com>,
        Thinh Nguyen <thinhn@synopsys.com>,
        Tejas Joglekar <tejas.joglekar@synopsys.com>,
        Ajay Yugalkishore Pandey <APANDEY@xilinx.com>
Subject: RE: [PATCH v7 09/10] usb: dwc3: Check for IOC/LST bit in both
 event->status and TRB->ctrl fields
Thread-Topic: [PATCH v7 09/10] usb: dwc3: Check for IOC/LST bit in both
 event->status and TRB->ctrl fields
Thread-Index: AQHUiWbqDI9WfI74TEmPyd+V2NlqDqVv4SkAgACgrWA=
Date:   Wed, 5 Dec 2018 19:01:12 +0000
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Hi Felipe,
>-----Original Message-----
>From: Felipe Balbi [mailto:balbi@kernel.org]
>Sent: Wednesday, December 05, 2018 2:38 PM
>To: Anurag Kumar Vulisha <anuragku@xilinx.com>; Greg Kroah-Hartman
><gregkh@linuxfoundation.org>; Shuah Khan <shuah@kernel.org>; Alan Stern
><stern@rowland.harvard.edu>; Johan Hovold <johan@kernel.org>; Jaejoong Kim
><climbbb.kim@gmail.com>; Benjamin Herrenschmidt <benh@kernel.crashing.org>=
;
>Roger Quadros <rogerq@ti.com>; Manu Gautam <mgautam@codeaurora.org>;
>martin.petersen@oracle.com; Bart Van Assche <bvanassche@acm.org>; Mike
>Christie <mchristi@redhat.com>; Matthew Wilcox <willy@infradead.org>; Coli=
n Ian
>King <colin.king@canonical.com>
>Cc: linux-usb@vger.kernel.org; linux-kernel@vger.kernel.org;
>v.anuragkumar@gmail.com; Thinh Nguyen <thinhn@synopsys.com>; Tejas Jogleka=
r
><tejas.joglekar@synopsys.com>; Ajay Yugalkishore Pandey <APANDEY@xilinx.co=
m>;
>Anurag Kumar Vulisha <anuragku@xilinx.com>
>Subject: Re: [PATCH v7 09/10] usb: dwc3: Check for IOC/LST bit in both eve=
nt->status
>and TRB->ctrl fields
>
>
>Hi,
>
>Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com> writes:
>> The present 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 makes the remaining
>> TRBs left unhandled.
>> To aviod this, changed the code to check for IOC/LST bits in both
>> event->status & TRB->ctrl. This patch does the same.
>>
>> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>
>> Reviewed-by: Thinh Nguyen <thinhn@synopsys.com>
>> Tested-by: Tejas Joglekar <tejas.joglekar@synopsys.com>
>> ---
>>  Changes in v7:
>> 	1. None
>>
>>  Changes in v6:
>> 	1. None
>>
>>  Changes in v5:
>> 	1. None
>>
>>  Changes in v4:
>> 	1. None
>>
>>  Changes in v3:
>> 	1. None
>>
>>  Changes in v2:
>> 	1. None
>> ---
>>  drivers/usb/dwc3/gadget.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 9ddc9fd..216179e 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2286,7 +2286,12 @@ 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 | DEPEVT_STATUS_LST))
>> +	if ((event->status & DEPEVT_STATUS_IOC) &&
>> +	    (trb->ctrl & DWC3_TRB_CTRL_IOC))
>> +		return 1;
>
>this shouldn't be necessary. According to databook, event->status
>contains the bits from the completed TRB.  Which means that
>event->status & IOC will always be equal to trb->ctrl & IOC.
>
Thanks for reviewing this patch. Lets consider an example where a request
has num_sgs > 0 and each sg is mapped to a TRB and the last TRB has the
IOC bit set. Once the controller is done with the transfer, it  generates=20
XferInProgress for the last TRB (since IOC bit is set). As a part of trb re=
claim
process  dwc3_gadget_ep_reclaim_trb_sg() calls
dwc3_gadget_ep_reclaim_completed_trb() for req->num_sgs times. Since
the event already has the IOC bit set, the loop is exited from the loop at =
the
very first TRB and the remaining TRBs (mapped to the sglist) are left unhan=
dled.
To avoid this we modified the code to exit only if both TRB & event has the=
 IOC
bit set.
=20
>Can you further describe the situation here? Perhaps share tracepoints
>exposing the problem?

Sure, will capture the traces and reply back

Thanks,
Anurag Kumar Vulisha