On Mon, Jun 08, 2020 at 11:58:40AM +0800, Kai-Heng Feng wrote: > > > > On May 20, 2020, at 18:18, Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> wrote: > > > > USB2 devices with LPM enabled may interrupt the system suspend: > > [ 932.510475] usb 1-7: usb suspend, wakeup 0 > > [ 932.510549] hub 1-0:1.0: hub_suspend > > [ 932.510581] usb usb1: bus suspend, wakeup 0 > > [ 932.510590] xhci_hcd 0000:00:14.0: port 9 not suspended > > [ 932.510593] xhci_hcd 0000:00:14.0: port 8 not suspended > > .. > > [ 932.520323] xhci_hcd 0000:00:14.0: Port change event, 1-7, id 7, portsc: 0x400e03 > > .. > > [ 932.591405] PM: pci_pm_suspend(): hcd_pci_suspend+0x0/0x30 returns -16 > > [ 932.591414] PM: dpm_run_callback(): pci_pm_suspend+0x0/0x160 returns -16 > > [ 932.591418] PM: Device 0000:00:14.0 failed to suspend async: error -16 > > > > During system suspend, USB core will let HC suspends the device if it > > doesn't have remote wakeup enabled and doesn't have any children. > > However, from the log above we can see that the usb 1-7 doesn't get bus > > suspended due to not in U0. After a while the port finished U2 -> U0 > > transition, interrupts the suspend process. > > > > The observation is that after disabling LPM, port doesn't transit to U0 > > immediately and can linger in U2. xHCI spec 4.23.5.2 states that the > > maximum exit latency for USB2 LPM should be BESL + 10us. The BESL for > > the affected device is advertised as 400us, which is still not enough > > based on my testing result. > > > > So let's use the maximum permitted latency, 10000, to poll for U0 > > status to solve the issue. > > > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> > > A gentle ping... It is the middle of the merge window, we can't do anything with any new patch until after -rc1 is out. You know this... greg k-h
