linux-kernel - Re: [PATCH 3.12 033/118] usb: xhci: Link TRB must not occur within a USB payload burst [NEW HARDWARE]

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Date:	Sat, 18 Jan 2014 10:34:16 -0800
From:	walt <w41ter@...il.com>
To:	David Laight <David.Laight@...LAB.COM>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>
CC:	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH 3.12 033/118] usb: xhci: Link TRB must not occur within
 a USB payload burst [NEW HARDWARE]

On 01/17/2014 06:34 AM, David Laight wrote:
> From: walt
>> Oy, Sarah! ;)  I put the ASMedia adapter in my older amd64 machine, and, well,
>> the stupid thing Just Works(TM) with kernel 3.12.7!  (Yes, with the same disk
>> docking station, too.)
>>
>> I can't believe the adapter works perfectly in a different computer.  Have you
>> seen this kind of thing before?
> 
> Could be a horrid timing race between the cpu and xchi controller.
> If the cpu manages to write a NOP or LINK TRB for a following transfer
> before the controller polls the next entry (after raising the IRQ)
> then the controller might process the LINK and then get confused
> when it can't process the linked-to TRB.
> This might not sound likely, but PCIe has significant latency.

 
> Can you try the patch I posted that stops the ownership on LINK TRBs
> being changed before that on the linked-to TRB?

David, the patch doesn't apply cleanly to any 3.12.x sources I can find,
including the latest git from Linus.  Half of the hunks fail.  Could you
create a fresh patch against vanilla 3.12.8 so I can test it? Or point me
to the correct kernel sources, perhaps.

Thanks.


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