On Fri, Oct 18, 2013 at 3:06 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Fri, 18 Oct 2013, Andiry Xu wrote: > >> On Wed, Oct 16, 2013 at 9:14 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> > Sarah: >> > >> > While working on some general fixes for wakeup races during PCI >> > suspend, I noticed that xhci_pci_suspend() ignores its do_wakeup >> > argument. What's the story? >> > >> >> I believe it's simply because I don't know how to handle the argument >> when I wrote the code (Ohci ignores it as well). > > Ah... Maybe there really is nothing to do. > > I was thinking of ehci-hcd. Its suspend routine turns off the wakeup > flags for all the ports if do_wakeup is false. Here's why: > > Consider the fifth line of Table 10 in section 4.15.2.3 (Wakeup Events) > of the xHCI spec. It says that if a port is disconnected with the WCE > bit set to 1, and a connect occurs while the host controller is not > in D0, then (Note 10-2) PME# is asserted if enabled. The EHCI spec > says essentially the same thing. > > With EHCI controllers on Intel motherboards, though, if the system is > in S3 under those same conditions, a connect will cause the system to > wake up even if PME# isn't enabled! I don't know if PME# gets asserted > too. Probably not, since it doesn't get asserted if the same thing > happens while the system is in S0. I also don't know whether Intel > considers this to be a bug in the hardware. > > To prevent these unwanted wakeups, we have to turn off the wakeup flags > for the suspended ports. Have you checked whether the same thing > is needed with xHCI? > > Here's an easy way to find out. Write "enabled" to the power/wakeup > sysfs file for each of your xHCI root hubs, and make sure that > power/wakeup for the controller device (the root hubs' parent) is set > to "disabled". Put the system into S3 suspend, and then see whether > plugging a device into one of the xHCI ports causes the system to wake > up. > Interesting. I used the following commands: #echo disabled > /sys/bus/pci/devices/0000:00:14.0/power/wakeup #echo enabled > /sys/bus/pci/devices/0000:00:14.0/usb3/power/wakeup #echo enabled > /sys/bus/pci/devices/0000:00:14.0/usb4/power/wakeup And a device plugging to xHCI port does wakeup the system from S3. The test is performed on a Intel HM76 chipset. So it means xHCI driver should clear wakeup flags for suspended ports in this case, just like ehci driver does. Correct? Thanks, Andiry -- 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
