From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Subject: Re: Help testing for USB ethernet/xHCI regression
Date: Fri, 31 Jan 2014 10:37:47 -0800
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Cc: Paul Zimmerman <paulz@synopsys.com>,
	David Laight <David.Laight@ACULAB.COM>,
	"renevant@internode.on.net" <renevant@internode.on.net>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>
To: Mark Lord <mlord@pobox.com>
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On Thu, Jan 30, 2014 at 09:32:49PM -0500, Mark Lord wrote:
> On 14-01-30 06:26 PM, Sarah Sharp wrote:
> > On Thu, Jan 30, 2014 at 05:20:40PM -0500, Mark Lord wrote:
> >> On 14-01-30 04:41 PM, Sarah Sharp wrote:
> >>>
> >>> Mark and David, can you pull the 3.13-td-changes-reverted branch again,
> >>> and see if the latest patch fixes your issue?  It disables scatter
> >>> gather for the ax88179_178a device, but only when it's operating at USB
> >>> 3.0 speeds.
> >>
> >> As expected, this works just fine.
> > 
> > Did it work when plugged into a USB 2.0 hub?
> 
> Curiosity, NO.  Dies almost immediately when run at USB 2.0 Hi-Speed.
> With a USB 2.0 hub, with a USB 2.0 port on a USB 3.0 hub,
> and with a USB 2.0 extension cable in place of a hub.
> 
> Near instant hangs.
> 
> Plugged directly to the USB 3.0 port, it works fine.

Ok, that makes sense.  The patch I wrote only limited scatter-gather at
USB 3.0 speeds, to see if scatter-gather could work at USB 2.0 speeds.
Reverting commit 3804fad45411b48233b48003e33a78f290d227c8 "USBNET:
ax88179_178a: enable tso if usb host supports sg dma" is the right way
to go instead.

Sarah Sharp