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

[Fabio Estevam]

Hi Xu Yang,

On Tue, Feb 24, 2026 at 12:17 AM Xu Yang <xu.yang_2@xxxxxxx> wrote:
>
> 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>

On an imx6x-sdb board, I still get the inconsistency below even after
applying your patch:

# echo 1 >  /sys/bus/usb/devices/1-0\:1.0/usb1-port1/disable
[   20.656414] usb 1-1: USB disconnect, device number 2

# echo 1 >  /sys/bus/usb/devices/1-0\:1.0/usb1-port1/disable
[   28.263516] usb 1-1: new high-speed USB device number 3 using ci_hdrc
[   28.466813] usb 1-1: New USB device found, idVendor=0457,
idProduct=0151, bcdDevice= 1.00
[   28.466949] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[   28.467039] usb 1-1: Product: USB Mass Storage Device
[   28.467086] usb 1-1: Manufacturer: USBest Technology
[   28.467126] usb 1-1: SerialNumber: 000000000003FF
[   28.501826] usb-storage 1-1:1.0: USB Mass Storage device detected
[   28.510452] usb-storage 1-1:1.0: Quirks match for vid 0457 pid 0151: 80
[   28.517597] scsi host0: usb-storage 1-1:1.0
[   28.524066] usb 1-1: USB disconnect, device number 3

# echo 1 >  /sys/bus/usb/devices/1-0\:1.0/usb1-port1/disable
# [   35.323593] usb 1-1: new high-speed USB device number 4 using ci_hdrc
[   35.526916] usb 1-1: New USB device found, idVendor=0457,
idProduct=0151, bcdDevice= 1.00
[   35.527054] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[   35.527150] usb 1-1: Product: USB Mass Storage Device
[   35.527198] usb 1-1: Manufacturer: USBest Technology
[   35.527239] usb 1-1: SerialNumber: 000000000003FF
[   35.562024] usb-storage 1-1:1.0: USB Mass Storage device detected
[   35.570430] usb-storage 1-1:1.0: Quirks match for vid 0457 pid 0151: 80
[   35.577562] scsi host0: usb-storage 1-1:1.0
[   36.645798] scsi 0:0:0:0: Direct-Access     Ut163
USB2FlashStorage 0.00 PQ: 0 ANSI: 2

# [   36.682705] sd 0:0:0:0: [sda] 248000 512-byte logical blocks:
(127 MB/121 MiB)
[   36.691645] sd 0:0:0:0: [sda] Write Protect is off
[   36.697915] sd 0:0:0:0: [sda] Asking for cache data failed
[   36.697981] sd 0:0:0:0: [sda] Assuming drive cache: write through
[   36.735520]  sda: sda1
[   36.739376] sd 0:0:0:0: [sda] Attached SCSI removable disk

# echo 1 >  /sys/bus/usb/devices/1-0\:1.0/usb1-port1/disable
[   39.423511] usb 1-1: USB disconnect, device number 4

Please try disabling the port several times in a row.