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

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
Date: Sat, 8 Dec 2018 19:03:33 +0000	[thread overview]
Message-ID: <BL0PR02MB56331B2ECFFEB96A99936C32A7AB0@BL0PR02MB5633.namprd02.prod.outlook.com> (raw)
In-Reply-To: <874lbpx3vg.fsf@linux.intel.com>


HI Felipe,

>-----Original Message-----
>From: Felipe Balbi [mailto:balbi@kernel.org]
>Sent: Friday, December 07, 2018 11:42 AM
>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>; Colin 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 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
>
>
>Hi,
>
>Anurag Kumar Vulisha <anuragku@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
