linux-kernel - Re: [Stable-review] [39/45] OHCI: work around for nVidia shutdown problem

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Date:	Sat, 20 Nov 2010 02:52:37 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org,
	David Brownell <david-b@...bell.net>,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	stable-review@...nel.org, alan@...rguk.ukuu.org.uk,
	Greg KH <gregkh@...e.de>
Subject: Re: [Stable-review] [39/45] OHCI: work around for nVidia shutdown
 problem

On Fri, 2010-11-19 at 13:43 -0800, Greg KH wrote:
> 2.6.32-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.
[...]

This last bit seems like a major change in behaviour, and this commit
has only just gone into the 2.6.37 cycle.  How thoroughly has this been
tested on other OHCI controllers?  Wouldn't it make more sense to use
the same quirk condition?

Ben.

-- 
Ben Hutchings
Once a job is fouled up, anything done to improve it makes it worse.

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