Re: rt8192cu on USB3

[Larry Finger <Larry.Finger@lwfinger.net>]

On 03/23/2012 03:34 PM, Sarah Sharp wrote:
> On Thu, Mar 22, 2012 at 09:24:31PM -0500, Larry Finger wrote:
>> On 03/22/2012 05:31 PM, Sarah Sharp wrote:
>>
>>> Larry, if the driver doesn't cancel an URB that the device doesn't
>>> respond to, then it will just be left on the endpoint ring.  If the
>>> driver then tries to queue new transfers to that same endpoint, but the
>>> device keeps NAKing the uncancelled transfer, then the endpoint ring
>>> would fill up with unanswered transfers.
>>>
>>> Perhaps some userspace or kernel portion is forgetting to cancel URBs
>>> before moving onto the next thing?  You said you moved to asynchronous
>>> transfers, so maybe the problem lies there?
>>
>> The writes have always been asynchronous and reads are synchronous.
>> The only change was to convert the firmware uploading writes from
>> 32-bits at a time into block writes of 1000+ 32-bit words.
>
> Yeah, that's going to cause the out-of-room warning under xHCI.  That
> should be fixed in the 3.4-rc1 kernel though.
>
>> Would xhci be worse that ohci or ehci in terms of the device not
>> responding to URBs? We only see problems with USB3.0 hubs, never
>> with 2.0 or 1.1.
>
> That's because EHCI handles arbitrarily large transfers, and xHCI didn't
> until now.
>
>> I am looking into changing the writes to be synchronous. That should
>> clear up any problems.
>
> Yeah, your problem probably was in the bulk large transfer, not the
> unfinished canceled URBs.  I would suggest getting your reporters to
> just try 3.4-rc1 and see if it helps before doing too much work to debug
> this.

Interesting in that I switched to the large bulk transfers AFTER the problems 
with xHCI were reported. I guess my attempts to fix the problem only made it worse.

Larry