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

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Date:	Sat, 20 Nov 2010 11:51:39 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Ben Hutchings <ben@...adent.org.uk>
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 Sat, 20 Nov 2010, Ben Hutchings wrote:

> 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 is right; let's hold off on putting this patch into any of the 
stable kernels.  There has been a bug report submitted against it, 
Bugzilla #22562.

Alan Stern

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