The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b3d71abd135e6919ca0b6cab463738472653ddfb Mon Sep 17 00:00:00 2001

From: Kai-Heng Feng kai.heng.feng@canonical.com Date: Wed, 24 Jun 2020 16:59:49 +0300 Subject: [PATCH] xhci: Poll for U0 after disabling USB2 LPM

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.

Cc: stable@vger.kernel.org Signed-off-by: Kai-Heng Feng kai.heng.feng@canonical.com Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com Link: https://lore.kernel.org/r/20200624135949.22611-6-mathias.nyman@linux.intel.c... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c index f97106e2860f..ed468eed299c 100644 --- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -4475,6 +4475,9 @@ static int xhci_set_usb2_hardware_lpm(struct usb_hcd *hcd, mutex_lock(hcd->bandwidth_mutex); xhci_change_max_exit_latency(xhci, udev, 0); mutex_unlock(hcd->bandwidth_mutex); + readl_poll_timeout(ports[port_num]->addr, pm_val, + (pm_val & PORT_PLS_MASK) == XDEV_U0, + 100, 10000); return 0; } }