linux-kernel - Re: DWC3 linux driver query

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Message-ID: <20150528141147.GC13729@saruman.tx.rr.com>
Date:	Thu, 28 May 2015 09:11:47 -0500
From:	Felipe Balbi <balbi@...com>
To:	sundeep subbaraya <sundeep.lkml@...il.com>
CC:	"balbi@...com" <balbi@...com>,
	Paul Zimmerman <Paul.Zimmerman@...opsys.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: DWC3 linux driver query

Hi,

On Thu, May 28, 2015 at 04:53:09PM +0530, sundeep subbaraya wrote:
> Hi Felipe and Paul,

btw, Paul has left Synopys :-)

> I am seeing an issue while testing iperf for USB ethernet gadget with
> dwc3 controller in 2.0 mode. After debugging I figured out that:
> 
> 1. Network gadget queues say 3 requests. (for IN endpoint)
> 2. It turns out with req.no_interrupt flag,
>     DWC3 driver issues START_TRANSFER with req0:IOC, req1, req2:LST
> 3. As per driver state machine, we get XFERNOTREADY then prepare these
> TRBs and issue start transfer. Make Endpoint state as Busy.
> 4. Endpoint state is set to free in XFERINPROGRESS or XFERCOMPLETE event.
> 5. The issue I see here is there are NAKs going to host (seen in
> analyzer) in between req0 and req2 hence XFERNOTREADY(Transfer Active)
> events in between XFERINPROGRESS and          XFERCOMPLETE  events.
> 6. As a result, EP is set as free in XFERINPROGRESS, since EP is free
> start transfer command is issued in XFERNOTREADY handler.The command
> fails since controller did not release the xfer resource yet.
> 
> I feel controller behaviour is fine since it sends NAK and writes that
> event. Driver may have to be modified to make EP as free only in
> XFERCOMPLETE event handler (ofcourse not for Isoc).

this sounds like the correct solution.

> Note I am testing on a platform which is very slow (the interface
> between DDR and core runs at 4Mhz).

sweet :-)

> Where as on Zynq (DWC3 in PL), a faster system compared to above one I

hey, when will we see a glue layer for Zynq ? :-)

> do not see any NAKs in between Start transfer command and XFERCOMPLETE
> event.
> 
> What do you guys say? Do you agree linux driver has to be modified or
> Core should never issue NAKs in between Start transfer and
> XFERCOMPLETE?

well, if we queued enough transfers, it shouldn't NAK. OTOH, we
shouldn't allow for a new StartTransfer command until all pending
requests have been transferred.

> A patch correcting DEPCMD status macros has been applied. Thank you
> Felipe for trace points in driver otherwise it would have taken very
> long time to figure out the root cause :) .

yeah, those are really helpful :-)

> Below is the trace log:(enabled only for IN bulk endpoint)
> 
>      irq/97-dwc3-1308  [001] d...   553.713513: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Not Active
>      irq/97-dwc3-1308  [001] d...   553.713768: dwc3_msg: ep1in-bulk:
> req ffffffc039a68580 dma 011c60a2 length 1558 IOC
> 
>      irq/97-dwc3-1308  [001] d...   553.714266: dwc3_msg: ep1in-bulk:
> req ffffffc039a687c0 dma 011c10a2 length 1558
> 
>      irq/97-dwc3-1308  [001] d...   553.714753: dwc3_msg: ep1in-bulk:
> req ffffffc039a68700 dma 011c18a2 length 1558 last IOC
> 
>      irq/97-dwc3-1308  [001] d...   553.717768: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Active
>      irq/97-dwc3-1308  [001] d...   553.718203: dwc3_msg: ep1in-bulk EP BUSY
>      irq/97-dwc3-1308  [001] d...   553.718412: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Active
>      irq/97-dwc3-1308  [001] d...   553.718638: dwc3_msg: ep1in-bulk EP BUSY
>      irq/97-dwc3-1308  [001] d...   553.718837: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Active
>      irq/97-dwc3-1308  [001] d...   553.719049: dwc3_msg: ep1in-bulk EP BUSY
>      irq/97-dwc3-1308  [001] d...   553.719248: dwc3_msg: ep1in-bulk
> XFERINPROGRESS
>      irq/97-dwc3-1308  [001] d...   553.719520: dwc3_msg: request
> ffffffc039a68580 from ep1in-bulk completed 1558/1558 ===> 0
> 
>      irq/97-dwc3-1308  [001] d...   553.720225: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Active
>      irq/97-dwc3-1308  [001] d...   553.720612: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Active
>      irq/97-dwc3-1308  [001] d...   553.720826: dwc3_msg: ep1in-bulk EP BUSY
>      irq/97-dwc3-1308  [001] d...   553.721026: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Active
>      irq/97-dwc3-1308  [001] d...   553.721243: dwc3_msg: ep1in-bulk EP BUSY
>      irq/97-dwc3-1308  [001] d...   553.721446: dwc3_msg: ep1in-bulk
> XFERCOMPLETE
>      irq/97-dwc3-1308  [001] d...   553.721711: dwc3_msg: request
> ffffffc039a687c0 from ep1in-bulk completed 1558/1558 ===> 0
> 
>      irq/97-dwc3-1308  [001] d...   553.722411: dwc3_msg: request
> ffffffc039a68700 from ep1in-bulk completed 1558/1558 ===> 0
> 
>      irq/97-dwc3-1308  [001] d...   553.722910: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Not Active
>      irq/97-dwc3-1308  [001] d...   553.723159: dwc3_msg: ep1in-bulk:
> req ffffffc039a68ac0 dma 398b18a2 length 1558
> 
>      irq/97-dwc3-1308  [001] d...   553.723649: dwc3_msg: ep1in-bulk:
> req ffffffc039a68c40 dma 3a1ce8a2 length 1558
> 
>      irq/97-dwc3-1308  [001] d...   553.724136: dwc3_msg: ep1in-bulk:
> req ffffffc039a68580 dma 3cc258a2 length 1558 last
> 
>      irq/97-dwc3-1308  [001] d...   553.724722: dwc3_msg: CMD Error:1 for ep 3
>      irq/97-dwc3-1308  [001] d...   553.727245: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Active
>      irq/97-dwc3-1308  [001] d...   553.727767: dwc3_msg: CMD Error:1 for ep 3
>      irq/97-dwc3-1308  [001] d...   553.728049: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Active
>      irq/97-dwc3-1308  [001] d...   553.728394: dwc3_msg: CMD Error:1 for ep 3
>      irq/97-dwc3-1308  [001] d...   553.731226: dwc3_msg: ep1in-bulk
> XFERNOTREADY.Transfer Active
>      irq/97-dwc3-1308  [001] d...   553.731658: dwc3_msg: CMD Error:1 for ep 3

Can you try patch below ?

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index a03a485205c7..cad747865ce0 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1907,12 +1907,16 @@ static void dwc3_endpoint_transfer_complete(struct dwc3 *dwc,
 {
 	unsigned		status = 0;
 	int			clean_busy;
+	u32			is_xfer_complete;
+
+	is_xfer_complete = (event->endpoint_event == DWC3_DEPEVT_XFERCOMPLETE);
 
 	if (event->status & DEPEVT_STATUS_BUSERR)
 		status = -ECONNRESET;
 
 	clean_busy = dwc3_cleanup_done_reqs(dwc, dep, event, status);
-	if (clean_busy)
+	if (clean_busy & (is_xfer_complete ||
+				usb_endpoint_xfer_isoc(dep->endpoint.desc)))
 		dep->flags &= ~DWC3_EP_BUSY;
 
 	/*

-- 
balbi

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