ained 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. Reference: https://bugzilla.kernel.org/show_bug.cgi?id=37632 Reference: https://bugzilla.kernel.org/show_bug.cgi?id=42728 Based-on-patch-by: AceLan Kao Signed-off-by: Alan Stern Tested-by: Dâniel Fraga Tested-by: Javier Marcet Tested-by: Andrey Rahmatullin Tested-by: Oleksij Rempel Tested-by: Pavel Pisa Cc: stable Acked-by: Bjorn Helgaas Acked-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman gM-