RE: [PATCH v7 09/10] usb: dwc3: Check for IOC/LST bit in both event->status and TRB->ctrl fields

[Anurag Kumar Vulisha]

HI Felipe,

>-----Original Message-----
>From: Felipe Balbi [mailto:ba...@kernel.org]
>Sent: Friday, December 07, 2018 11:42 AM
>To: Anurag Kumar Vulisha <anura...@xilinx.com>; Greg Kroah-Hartman
><gre...@linuxfoundation.org>; Shuah Khan <sh...@kernel.org>; Alan Stern
><st...@rowland.harvard.edu>; Johan Hovold <jo...@kernel.org>; Jaejoong Kim
><climbbb....@gmail.com>; Benjamin Herrenschmidt <b...@kernel.crashing.org>;
>Roger Quadros <rog...@ti.com>; Manu Gautam <mgau...@codeaurora.org>;
>martin.peter...@oracle.com; Bart Van Assche <bvanass...@acm.org>; Mike
>Christie <mchri...@redhat.com>; Matthew Wilcox <wi...@infradead.org>; Colin Ian
>King <colin.k...@canonical.com>
>Cc: linux-...@vger.kernel.org; linux-kernel@vger.kernel.org;
>v.anuragku...@gmail.com; Thinh Nguyen <thi...@synopsys.com>; Tejas Joglekar
><tejas.jogle...@synopsys.com>; Ajay Yugalkishore Pandey <apan...@xilinx.com>
>Subject: RE: [PATCH v7 09/10] usb: dwc3: Check for IOC/LST bit in both 
>event->status
>and TRB->ctrl fields
>
>
>Hi,
>
>Anurag Kumar Vulisha <anura...@xilinx.com> writes:
>>>> @@ -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 XferInProgress for the last TRB (since IOC bit
>> is set). As a part of trb reclaim 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
>unhandled.
>> To avoid this we modified the code to exit only if both TRB & event
>> has the IOC bit set.
>
>Seems like IOC case should just test for chain flag as well:
>

Okay. Along with this logic the code for updating chain bit should also be 
modified I guess.
Since the IOC bit is also set when there are not enough TRBs available, the 
code should be
modified to not set DWC3_TRB_CTRL_CHN bit when the IOC bit is set. I will 
update below
changes along with your suggestions and resend the patches.

@@ -998,7 +998,7 @@ static void __dwc3_prepare_one_trb(struct dwc3_ep *dep, 
struct dwc3_trb *trb,
                        (dwc3_calc_trbs_left(dep) == 1))
                trb->ctrl |= DWC3_TRB_CTRL_IOC;
 
-       if (chain)
+       if (chain && !(trb->ctrl & DWC3_TRB_CTRL_IOC))
                trb->ctrl |= DWC3_TRB_CTRL_CHN;
 
        if (usb_endpoint_xfer_bulk(dep->endpoint.desc) && dep->stream_capable)
@@ -2372,7 +2372,7 @@ 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 (event->status & DEPEVT_STATUS_IOC && !chain)
                return 1;
 
        return 0;
@@ -2399,7 +2399,7 @@ static int dwc3_gadget_ep_reclaim_trb_sg(struct dwc3_ep 
*dep,
                req->num_pending_sgs--;
 
                ret = dwc3_gadget_ep_reclaim_completed_trb(dep, req,
-                               trb, event, status, true);
+                               trb, event, status, (trb & DWC3_TRB_CTRL_CHN));
                if (ret)
                        break;
        }

Thanks,
Anurag Kumar Vulisha

>modified   drivers/usb/dwc3/gadget.c
>@@ -2372,7 +2372,7 @@ 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 (event->status & DEPEVT_STATUS_IOC && !chain)
>               return 1;
>
>       return 0;
>
>--
>balbi