On Tue, Jul 10, 2012 at 09:32:59AM -0600, Bjorn Helgaas wrote: > On Mon, Jul 9, 2012 at 10:47 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Mon, Jul 09, 2012 at 06:50:24PM +0200, Rafael J. Wysocki wrote: > >> On Monday, July 09, 2012, Alan Stern wrote: > >> > 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. > >> > > >> > Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > >> > Tested-by: Dâniel Fraga <fragabr@xxxxxxxxx> > >> > Tested-by: Javier Marcet <jmarcet@xxxxxxxxx> > >> > Tested-by: Andrey Rahmatullin <wrar@xxxxxxxxx> > >> > Tested-by: Oleksij Rempel <bug-track@xxxxxxxxxxxxxxxxx> > >> > Tested-by: Pavel Pisa <pisa@xxxxxxxxxxxxxxxx> > >> > CC: <stable@xxxxxxxxxxxxxxx> > >> > >> Acked-by: Rafael J. Wysocki <rjw@xxxxxxx> > > > > Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > I'm fine with this patch. I was going to add these: > > Based-on-patch-by: AceLan Kao <acelan.kao@xxxxxxxxxxxxx> > Reference: https://bugzilla.kernel.org/show_bug.cgi?id=37632 > Reference: https://bugzilla.kernel.org/show_bug.cgi?id=42728 > > I don't have the previous iteration (c2fb8a3fa25513d) in my "next" > branch. I think it went through you, Greg. Do you want to handle > this one as well? I can easily take it if you don't want to. > I *could* do it, but it looks like a messy merge -- I think I'd have > to rebase almost everything in my "next" branch -- so I'd rather not. > Of course, I do have some D3-related updates in pci_prepare_to_sleep() > which will conflict with this, too, so I guess it will be a bit of > work for somebody either way. Ick, no, don't rebase anything. If I take this then we will have merge issues in linux-next, which we can work out, and then we will have the same issues for 3.6-rc1 as well. Or, Alan can redo the patch based on your next branch, which might make it easier for everyone involved? Which ever you want to do is fine with me. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
