Re: xHCI regression in stable 3.13.5 with USB3 card reader (Bisected)

From: Sarah Sharp
Date: Thu Mar 06 2014 - 10:11:43 EST


[Adding Mathias.]

On Thu, Mar 06, 2014 at 12:27:59AM -0600, Robert Hancock wrote:
> On 05/03/14 11:17 PM, Robert Hancock wrote:
> >I have a USB 3.0 multi-card reader device:
> >
> >Bus 004 Device 002: ID 05e3:0743 Genesys Logic, Inc.
> >
> >which seems to work fine in 3.13.4 (Fedora version kernel-3.13.4-200
> >specifically) but fails in 3.13.5 (specifically kernel-3.13.5-202).
> >Below is what I get in dmesg. Essentially there's a bunch of
> >input/output errors making the reader mostly unusable.
> >
> >This is on an Intel Haswell machine with this controller:
> >
> >00:14.0 USB controller [0c03]: Intel Corporation 8 Series/C220 Series
> >Chipset Family USB xHCI [8086:8c31] (rev 05)
> >
> >It looks like there were some XHCI commits that went into 3.13.5 so it
> >seems likely one of those is the cause. I can try current git if there's
> >anything in there that's likely to fix it. But it does seem like a
> >regression got into the stable kernel in this respect.
>
> Bisecting between 3.13.4 and 3.13.5 gives me this:
>
> c8f44f98901994832ccecb87c3dd7900274b699a is the first bad commit
> commit c8f44f98901994832ccecb87c3dd7900274b699a
> Author: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
> Date: Fri Jan 31 11:26:25 2014 -0800
>
> xhci 1.0: Limit arbitrarily-aligned scatter gather.

Yes, this is a known regression. That commit should be reverted in
3.14-rc shortly, and the patch will be backported to stable kernels.
Mathias is taking over as xHCI maintainer, and he will queue the revert
patches to Greg shortly.

Sarah Sharp

>
> commit 247bf557273dd775505fb9240d2d152f4f20d304 upstream.
>
> xHCI 1.0 hosts have a set of requirements on how to align transfer
> buffers on the endpoint rings called "TD fragment" rules. When the
> ax88179_178a driver added support for scatter gather in 3.12, with
> commit 804fad45411b48233b48003e33a78f290d227c8 "USBNET: ax88179_178a:
> enable tso if usb host supports sg dma", it broke the device under xHCI
> 1.0 hosts. Under certain network loads, the device would see an
> unexpected short packet from the host, which would cause the device to
> stop sending ethernet packets, even through USB packets would still be
> sent.
>
> Commit 35773dac5f86 "usb: xhci: Link TRB must not occur within a USB
> payload burst" attempted to fix this. It was a quick hack to partially
> implement the TD fragment rules. However, it caused regressions in the
> usb-storage layer and userspace USB drivers using libusb. The patches
> to attempt to fix this are too far reaching into the USB core, and we
> really need to implement the TD fragment rules correctly in the xHCI
> driver, instead of continuing to wallpaper over the issues.
>
> Disable arbitrarily-aligned scatter-gather in the xHCI driver for 1.0
> hosts. Only the ax88179_178a driver checks the no_sg_constraint flag,
> so don't set it for 1.0 hosts. This should not impact usb-storage or
> usbfs behavior, since they pass down max packet sized aligned sg-list
> entries (512 for USB 2.0 and 1024 for USB 3.0).
>
> Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
> Tested-by: Mark Lord <mlord@xxxxxxxxx>
> Cc: David Laight <David.Laight@xxxxxxxxxx>
> Cc: Bjørn Mork <bjorn@xxxxxxx>
> Cc: Freddy Xin <freddy@xxxxxxxxxxx>
> Cc: Ming Lei <ming.lei@xxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>
>
>
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