netdev - RE: net/usb/ax88179_178a driver broken in linux-3.12

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Message-ID: <AE90C24D6B3A694183C094C60CF0A2F6026B7431@saturn3.aculab.com>
Date:	Tue, 19 Nov 2013 10:04:11 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Mark Lord" <mlord@...ox.com>,
	"Eric Dumazet" <eric.dumazet@...il.com>,
	"Ming Lei" <ming.lei@...onical.com>, <davem@...emloft.net>,
	<netdev@...r.kernel.org>
Subject: RE: net/usb/ax88179_178a driver broken in linux-3.12

> From: Mark Lord
> On 13-11-18 08:32 AM, David Laight wrote:
> >> From: David Laight
> >>> On 13-11-17 01:56 PM, Mark Lord wrote:
> >>>> On 13-11-17 01:35 PM, Mark Lord wrote:
> >>>>> The USB3 network adapter locks up consistently for me here in 3.12,
> >>>>> but was working without issues in 3.11.x
> >>
> >> The xhci driver is well broken in 3.12.
> >
> > To correct myself...
> >
> > The xhci driver has never correctly support scatter-gather requests.
> > In 3.12 code was added to usbnet to generate SG transmits, and to the
> > ax88179_178a driver to use them.
> > TCP segmentation offload was then enabled - with does generate
> > SG transfers.
> >
> > SG transfers for 'disks' almost certainly work because the
> > fragment boundaries are 'adequately aligned'.
> >
> > 	David
> >
> 
> Well, that's all very nice and whatnot,
> except the ax88179_178a driver still does not work in linux-3.12,
> whereas it works fine in all earlier kernels.
> 
> That's a regression.
> And a simple revert (earlier in this thread) fixes it.
> 
> So.. let's revert it for now, until a proper xhci compatible patch is produced.

Which changes did you revert?
I think you must have gone right back to the version that doesn't so scatter-gather.

There is a patch to xhci-ring.c that should fix the SG problem.
http://www.spinics.net/lists/linux-usb/msg97176.html

I think it should apply to the 3.12 sources.

Note that with older kernels the asix card I have will drop/discard
short bursts of tx/rx packets. I've not seen that with 3.12 and the
xhci-ring.c patch.

	David