mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-02-19 07:49:02 -05:00
31a6afbe86
Shawn and John reported a hang issue during system suspend as below:
- USB gadget is enabled as Ethernet
- There is data transfer over USB Ethernet (scp a big file between host
and device)
- Device is going in/out suspend (echo mem > /sys/power/state)
The root cause is the USB device controller is suspended but the USB bus
is still active which caused the USB host continues to transfer data with
device and the device continues to queue USB requests (in this case, a
delayed TCP ACK packet trigger the issue) after controller is suspended,
however the USB controller clock is already gated off. Then if udc driver
access registers after that point, the system will hang.
The correct way to avoid such issue is to disconnect device from host when
the USB bus is not at suspend state. Then the host will receive disconnect
event and stop data transfer in time. To continue make USB gadget device
work after system resume, this will reconnect device automatically.
To make usb wakeup work if USB bus is already at suspend state, this will
keep connection for it only when USB device controller has enabled wakeup
capability.
Reported-by: Shawn Guo <shawnguo@kernel.org>
Reported-by: John Ernberg <john.ernberg@actia.se>
Closes: https://lore.kernel.org/linux-usb/aEZxmlHmjeWcXiF3@dragon/
Tested-by: John Ernberg <john.ernberg@actia.se> # iMX8QXP
Fixes: 235ffc17d0 ("usb: chipidea: udc: add suspend/resume support for device controller")
Cc: stable <stable@kernel.org>
Reviewed-by: Jun Li <jun.li@nxp.com>
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Acked-by: Peter Chen <peter.chen@kernel.org>
Link: https://lore.kernel.org/r/20250614124914.207540-1-xu.yang_2@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.