lkml.org 
[lkml]   [2012]   [Jul]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [ 51/68] PCI: EHCI: fix crash during suspend on ASUS computers
On Thu, Jul 12, 2012 at 04:02:25PM -0700, Greg Kroah-Hartman wrote:
> From: Greg KH <gregkh@linuxfoundation.org>
>
> 3.0-stable review patch. If anyone has any objections, please let me know.
>
> ------------------

Missing also the diff/"signoff area" on this one.

>
> From: Alan Stern <stern@rowland.harvard.edu>
>
> commit dbf0e4c7257f8d684ec1a3c919853464293de66e upstream.
>
> Quite a few ASUS computers experience a nasty problem, related to the
> EHCI controllers, when going into system suspend. It was observed
> that the problem didn't occur if the controllers were not put into the
> D3 power state before starting the suspend, and commit
> 151b61284776be2d6f02d48c23c3625678960b97 (USB: EHCI: fix crash during
> suspend on ASUS computers) was created to do this.
>
> It turned out this approach messed up other computers that didn't have
> the problem -- it prevented USB wakeup from working. Consequently
> commit c2fb8a3fa25513de8fedb38509b1f15a5bbee47b (USB: add
> NO_D3_DURING_SLEEP flag and revert 151b61284776be2) was merged; it
> reverted the earlier commit and added a whitelist of known good board
> names.
>
> Now we know the actual cause of the problem. Thanks to AceLan Kao for
> tracking it down.
>
> According to him, an engineer at ASUS explained that some of their
> BIOSes contain a bug that was added in an attempt to work around a
> problem in early versions of Windows. When the computer goes into S3
> suspend, the BIOS tries to verify that the EHCI controllers were first
> quiesced by the OS. Nothing's wrong with this, but the BIOS does it
> by checking that the PCI COMMAND registers contain 0 without checking
> the controllers' power state. If the register isn't 0, the BIOS
> assumes the controller needs to be quiesced and tries to do so. This
> involves making various MMIO accesses to the controller, which don't
> work very well if the controller is already in D3. The end result is
> a system hang or memory corruption.
>
> Since the value in the PCI COMMAND register doesn't matter once the
> controller has been suspended, and since the value will be restored
> anyway when the controller is resumed, we can work around the BIOS bug
> simply by setting the register to 0 during system suspend. This patch
> (as1590) does so and also reverts the second commit mentioned above,
> which is now unnecessary.
>
> In theory we could do this for every PCI device. However to avoid
> introducing new problems, the patch restricts itself to EHCI host
> controllers.
>
> Finally the affected systems can suspend with USB wakeup working
> properly.
>
> --
> To unsubscribe from this list: send the line "unsubscribe stable" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>

--
[]'s
Herton


\
 
 \ /
  Last update: 2012-07-13 04:21    [W:0.214 / U:0.292 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site