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[ Upstream commitfb9acf5f1f] The code did not de-assert any CS GPIOs before probing slaves. This means that several CS signals could be active at once, garbling the communication. Whether this was actually a problem depended on the type of the SPI device attached (so my "spidev" for userspace access worked correctly because its probe was effectively a no-op), and on the state of the GPIO pins at SoC's boot. The code was already iterating through all DT children of the SPI controller, so this change re-uses that loop for CS GPIO setup as well. This means that this might change the number of the HW CS signal which is picked for all GPIO CS devices. Previously, the lowest one was used, but we now use the first one from the DT. With this move of the code, we can also finally initialize each GPIO CS lane before registering the SPI controller (which in turn probes for slaves). I tried to fix this in544248623balready, but that only did it half way by registering the GPIOs properly. That patch failed to set their logic signals early enough, though. Signed-off-by: Jan Kundrát <jan.kundrat@cesnet.cz> Signed-off-by: Mark Brown <broonie@kernel.org> Signed-off-by: Sasha Levin <alexander.levin@microsoft.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 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.