xhci: Add grace period after xHC start to prevent premature runtime suspend.
authorMathias Nyman <mathias.nyman@linux.intel.com>
Thu, 25 Aug 2022 15:08:39 +0000 (18:08 +0300)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 8 Sep 2022 10:28:06 +0000 (12:28 +0200)
commit3a6c5c5ab734dbe27bd4dede6def79c24154d049
tree4d0889c6b901ac22e50747c6f1db8c52ae438260
parent75913c562f5ba4cf397d835c63f443879167c6f6
xhci: Add grace period after xHC start to prevent premature runtime suspend.

commit 33e321586e37b642ad10594b9ef25a613555cd08 upstream.

After xHC controller is started, either in probe or resume, it can take
a while before any of the connected usb devices are visible to the roothub
due to link training.

It's possible xhci driver loads, sees no acivity and suspends the host
before the USB device is visible.

In one testcase with a hotplugged xHC controller the host finally detected
the connected USB device and generated a wake 500ms after host initial
start.

If hosts didn't suspend the device duringe training it probablty wouldn't
take up to 500ms to detect it, but looking at specs reveal USB3 link
training has a couple long timeout values, such as 120ms
RxDetectQuietTimeout, and 360ms PollingLFPSTimeout.

So Add a 500ms grace period that keeps polling the roothub for 500ms after
start, preventing runtime suspend until USB devices are detected.

Cc: stable@vger.kernel.org
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20220825150840.132216-3-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/usb/host/xhci-hub.c
drivers/usb/host/xhci.c
drivers/usb/host/xhci.h