linux-kernel - DWC3 linux driver query

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Date:	Thu, 28 May 2015 16:53:09 +0530
From:	sundeep subbaraya <sundeep.lkml@...il.com>
To:	"balbi@...com" <balbi@...com>,
	Paul Zimmerman <Paul.Zimmerman@...opsys.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: DWC3 linux driver query

Hi Felipe and Paul,

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).
Note I am testing on a platform which is very slow (the interface
between DDR and core runs at 4Mhz).
Where as on Zynq (DWC3 in PL), a faster system compared to above one I
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?

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 :) .
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



Thanks,
Sundeep
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