[PATCH 6.6 088/166] usb: port: add delay after usb_hub_set_port_power()

Greg Kroah-Hartman
2026-04-24T13:38:39Z

From: Xu Yang <xu.yang_2@nxp.com>

commit b84cc80610a8ce036deb987f056ce3196ead7f1e upstream.

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@kernel.org
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Link: https://patch.msgid.link/20260316095042.1559882-1-xu.yang_2@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/core/port.c | 1 +
1 file changed, 1 insertion(+)

--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -138,6 +138,7 @@ static ssize_t disable_store(struct devi
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);