[PATCH v2] usb: port: add delay after usb_hub_set_port_power()

[Xu Yang]

When a port is disabled, an attached device will be disconnected.  This
causes a port-status-change event, which will race with hub autosuspend
(if the disabled port was the only connected port on its hub), causing
an immediate resume and a second autosuspend.  Both of these can be
avoided by adding a short delay after the call to
usb_hub_set_port_power().

Below log shows what is happening:

$ echo 1 > usb1-port1/disable
[   37.958239] usb 1-1: USB disconnect, device number 2
[   37.964101] usb 1-1: unregistering device
[   37.970070] hub 1-0:1.0: hub_suspend
[   37.971305] hub 1-0:1.0: state 7 ports 1 chg 0000 evt 0002
[   37.974412] usb usb1: bus auto-suspend, wakeup 1
[   37.988175] usb usb1: suspend raced with wakeup event         <---
[   37.993947] usb usb1: usb auto-resume
[   37.998401] hub 1-0:1.0: hub_resume
[   38.105688] usb usb1-port1: status 0000, change 0000, 12 Mb/s
[   38.112399] hub 1-0:1.0: state 7 ports 1 chg 0000 evt 0000
[   38.118645] hub 1-0:1.0: hub_suspend
[   38.122963] usb usb1: bus auto-suspend, wakeup 1
[   38.200368] usb usb1: usb wakeup-resume
[   38.204982] usb usb1: usb auto-resume
[   38.209376] hub 1-0:1.0: hub_resume
[   38.213676] usb usb1-port1: status 0101 change 0001
[   38.321552] hub 1-0:1.0: state 7 ports 1 chg 0002 evt 0000
[   38.327978] usb usb1-port1: status 0101, change 0000, 12 Mb/s
[   38.457429] usb 1-1: new high-speed USB device number 3 using ci_hdrc

Then, port change bit will be fixed to the final state and
usb_clear_port_feature() can correctly clear it after this period. This
will also avoid usb runtime suspend routine to run because
usb_autopm_put_interface() not run yet.

Fixes: f061f43d7418 ("usb: hub: port: add sysfs entry to switch port power")
Cc: stable@xxxxxxxxxx
Signed-off-by: Xu Yang <xu.yang_2@xxxxxxx>

---
Changes in v2:
 - improve commit message
---
 drivers/usb/core/port.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 44e38f922bc5..027a5f21c5f7 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -141,6 +141,7 @@ static ssize_t disable_store(struct device *dev, struct device_attribute *attr,
 		usb_disconnect(&port_dev->child);
 
 	rc = usb_hub_set_port_power(hdev, hub, port1, !disabled);
+	msleep(2 * hub_power_on_good_delay(hub));
 
 	if (disabled) {
 		usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION);
-- 
2.34.1