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[ Upstream commit ceb94bc52c ]
This patch adds a safety connection way for "forced_b_device" with
"workaround_for_vbus" like below:
< Example for R-Car E3 Ebisu >
# modprobe <any usb gadget driver>
# echo 1 > /sys/kernel/debug/ee020000.usb/b_device
(connect a usb cable to host side.)
# echo 2 > /sys/kernel/debug/ee020000.usb/b_device
Previous code should have connected a usb cable before the "b_device"
is set to 1 on the Ebisu board. However, if xHCI driver on the board
is probed, it causes some troubles:
- Conflicts USB VBUS/signals between the board and another host.
- "Cannot enable. Maybe the USB cable is bad?" might happen on
both the board and another host with a usb hub.
- Cannot enumerate a usb gadget correctly because an interruption
of VBUS change happens unexpectedly.
Reported-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.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 Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
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.