[5/5] xhci: Poll for U0 after disabling USB2 LPM

Message ID 20200624135949.22611-6-mathias.nyman@linux.intel.com
State New
Headers show
Series
  • [1/5] xhci: Fix incorrect EP_STATE_MASK
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Commit Message

Mathias Nyman June 24, 2020, 1:59 p.m.
From: Kai-Heng Feng <kai.heng.feng@canonical.com>

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>
---
 drivers/usb/host/xhci.c | 3 +++
 1 file changed, 3 insertions(+)

Patch

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;
 		}
 	}