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[ Upstream commitb7badd752d] In the past setting the pin direction called pinctrl_gpio_direction() which uses a mutex to serialize this. That was changed to set the direction directly in the pin controller driver, but that lost the serialization mechanism. Since the direction of multiple pins are in the same register you can have a race condition, something that was in fact observed with the cec-gpio driver. Add a new spinlock to serialize writing to the FSEL registers. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Fixes:1a4541b68e("pinctrl-bcm2835: don't call pinctrl_gpio_direction()") Link: https://lore.kernel.org/r/4302b66b-ca20-0f19-d2aa-ee8661118863@xs4all.nl Signed-off-by: Linus Walleij <linus.walleij@linaro.org> 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.
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.