linux-kernel - Re: [patch 2/3] USB: xhci: Set change bit when warm reset change is set.

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Date:	Tue, 20 Sep 2011 15:22:07 +0400
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	Greg KH <gregkh@...e.de>
CC:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>, stable@...nel.org,
	Andiry Xu <andiry.xu@....com>,
	Randy Dunlap <rdunlap@...otime.net>
Subject: Re: [patch 2/3] USB: xhci: Set change bit when warm reset change
 is set.

Hello.

On 20-09-2011 3:05, Greg KH wrote:

    From: line is missing?

> Sometimes, when a USB 3.0 device is disconnected, the Intel Panther Point
> xHCI host controller will report a link state change with the state set
> to "SS.Inactive".  This causes the xHCI host controller to issue a warm
> port reset, which doesn't finish before the USB core times out while
> waiting for it to complete.

> When the warm port reset does complete, and the xHC gives back a port
> status change event, the xHCI driver kicks khubd.  However, it fails to
> set the bit indicating there is a change event for that port because the
> logic in xhci-hub.c doesn't check for the warm port reset bit.

> After that, the warm port status change bit is never cleared by the USB
> core, and the xHC stops reporting port status change bits.  (The xHCI spec
> says it shouldn't report more port events until all change bits are
> cleared.)  This means any port changes when a new device is connected will
> never be reported, and the port will seem "dead" until the xHCI driver is
> unloaded and reloaded, or the computer is rebooted.  Fix this by making
> the xHCI driver set the port change bit when a warm port reset change bit
> is set.

> A better solution would be to make the USB core handle warm port reset in
> differently, merging the current code with the standard port reset code
> that does an incremental backoff on the timeout, and tries to complete the
> port reset two more times before giving up.  That more complicated fix
> will be merged next window, and this fix will be backported to stable.

> This should be backported to kernels as old as 3.0, since that was the
> first kernel with commit a11496ebf37534177d67222285e8debed7a39788
> "xHCI: warm reset support".

> Signed-off-by: Sarah Sharp<sarah.a.sharp@...ux.intel.com>
> Cc: stable@...nel.org
> Signed-off-by: Greg Kroah-Hartman<gregkh@...e.de>

WBR, Sergei

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