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* [PATCH 1/2] xhci: Return if xHCI doesn't support LPM
@ 2020-05-20 10:18 Kai-Heng Feng
  2020-05-20 10:18 ` [PATCH 2/2] xhci: Poll for U0 after disabling USB2 LPM Kai-Heng Feng
  0 siblings, 1 reply; 2+ messages in thread
From: Kai-Heng Feng @ 2020-05-20 10:18 UTC (permalink / raw)
  To: mathias.nyman
  Cc: Kai-Heng Feng, Greg Kroah-Hartman, open list:USB XHCI DRIVER, open list

Just return if xHCI is quirked to disable LPM. We can save some time
from reading registers and doing spinlocks.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
 drivers/usb/host/xhci.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index bee5deccc83d..14181a7ea375 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4390,6 +4390,9 @@ static int xhci_set_usb2_hardware_lpm(struct usb_hcd *hcd,
 	int		hird, exit_latency;
 	int		ret;
 
+	if (xhci->quirks & XHCI_HW_LPM_DISABLE)
+		return -EPERM;
+
 	if (hcd->speed >= HCD_USB3 || !xhci->hw_lpm_support ||
 			!udev->lpm_capable)
 		return -EPERM;
@@ -4412,7 +4415,7 @@ static int xhci_set_usb2_hardware_lpm(struct usb_hcd *hcd,
 	xhci_dbg(xhci, "%s port %d USB2 hardware LPM\n",
 			enable ? "enable" : "disable", port_num + 1);
 
-	if (enable && !(xhci->quirks & XHCI_HW_LPM_DISABLE)) {
+	if (enable) {
 		/* Host supports BESL timeout instead of HIRD */
 		if (udev->usb2_hw_lpm_besl_capable) {
 			/* if device doesn't have a preferred BESL value use a
-- 
2.17.1


^ permalink raw reply	[flat|nested] 2+ messages in thread

* [PATCH 2/2] xhci: Poll for U0 after disabling USB2 LPM
  2020-05-20 10:18 [PATCH 1/2] xhci: Return if xHCI doesn't support LPM Kai-Heng Feng
@ 2020-05-20 10:18 ` Kai-Heng Feng
  0 siblings, 0 replies; 2+ messages in thread
From: Kai-Heng Feng @ 2020-05-20 10:18 UTC (permalink / raw)
  To: mathias.nyman
  Cc: Kai-Heng Feng, Greg Kroah-Hartman, open list:USB XHCI DRIVER, open list

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

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 14181a7ea375..1058f604975b 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4474,6 +4474,9 @@ 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;
 		}
 	}
-- 
2.17.1


^ permalink raw reply	[flat|nested] 2+ messages in thread

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2020-05-20 10:18 [PATCH 1/2] xhci: Return if xHCI doesn't support LPM Kai-Heng Feng
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