________________________________________ > From: Alan Stern [stern@xxxxxxxxxxxxxxxxxxx] > Sent: Friday, April 13, 2012 10:18 PM > To: Xu, Andiry > Cc: Greg KH; Sarah Sharp; USB list > Subject: Re: [PATCH 0/3] USB: fix race between root-hub suspend and remote wakeup > On Sat, 14 Apr 2012, Andiry Xu wrote: >> I've created the corresponding patch for xHCI, most codes and the >> description are copied from your patch for ehci-hcd. Seems remote wakeup >> works fine, but I don't know how to trigger the race case. So I sent it >> out as RFC. > The patch looks okay to me. > To trigger the race, add an ssleep(2) call (or something similar) to > the end of xhci_bus_suspend. Plug in a SuperSpeed hub, and attach some > other SuperSpeed device to the hub. > Then start a system suspend. During the elay caused by the ssleep > call, unplug the device from the hub. That should cause the hub to > generate a remote wakeup request, and if your patch works correctly > then the wakeup request will cause the system suspend to be aborted. I have doubt about this. Note xHCI has different remote wakeup mechanism for 3.0 port and 2.0 port. For 2.0 port, it's almost the same as EHCI: write resume state to PORTSC register and waiting for 20ms, then write U0 to the register. For SS port, it does not have this "20ms clock" mechanism, just write U0 to the register. The code change in the patch mainly cover the 2.0 port part. For 3.0 port behavior, I doubt there will be any difference with the patch. Or should I use a 2.0 hub and 2.0 device to verify the patch? 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
