linux-kernel - Re: [PATCH 039/173] OHCI: work around for nVidia shutdown problem

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Date:	Mon, 25 Apr 2011 17:24:34 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Willy Tarreau <w@....eu>
cc:	Kernel development list <linux-kernel@...r.kernel.org>,
	<stable@...nel.org>, <stable-review@...nel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH 039/173] OHCI: work around for nVidia shutdown problem

On Mon, 25 Apr 2011, Willy Tarreau wrote:

> 2.6.27.59-stable review patch.  If anyone has any objections, please let us know.
> 
> ------------------
> 
> From: Alan Stern <stern@...land.harvard.edu>
> 
> commit 3df7169e73fc1d71a39cffeacc969f6840cdf52b upstream.
> 
> This patch (as1417) fixes a problem affecting some (or all) nVidia
> chipsets.  When the computer is shut down, the OHCI controllers
> continue to power the USB buses and evidently they drive a Reset
> signal out all their ports.  This prevents attached devices from going
> to low power.  Mouse LEDs stay on, for example, which is disconcerting
> for users and a drain on laptop batteries.
> 
> The fix involves leaving each OHCI controller in the OPERATIONAL state
> during system shutdown rather than putting it in the RESET state.
> Although this nominally means the controller is running, in fact it's
> not doing very much since all the schedules are all disabled.  However
> there is ongoing DMA to the Host Controller Communications Area, so
> the patch also disables the bus-master capability of all PCI USB
> controllers after the shutdown routine runs.
> 
> The fix is applied only to nVidia-based PCI OHCI controllers, so it
> shouldn't cause problems on systems using other hardware.  As an added
> safety measure, in case the kernel encounters one of these running
> controllers during boot, the patch changes quirk_usb_handoff_ohci()
> (which runs early on during PCI discovery) to reset the controller
> before anything bad can happen.
> 
> Reported-by: Pali Rohár <pali.rohar@...il.com>
> Signed-off-by: Alan Stern <stern@...land.harvard.edu>
> CC: David Brownell <david-b@...bell.net>
> Tested-by: Pali Rohár <pali.rohar@...il.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

Some people have reported that more recent Nvidia systems work
correctly without this patch and have problems when the patch is
applied.  For now, I suggest omitting this patch.

Alan Stern

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