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[ Upstream commit 1248c9b8d54120950fda10fbeb98fb8932b4d45c ] There are spi devices with multiple frequency limitations depending on the invoked command. We probably do not want to afford running at the lowest supported frequency all the time, so if we want to get the most of our hardware, we need to allow per-operation frequency limitations. Among all the SPI memory controllers, I believe all are capable of changing the spi frequency on the fly. Some of the drivers do not make any frequency setup though. And some others will derive a per chip prescaler value which will be used forever. Actually changing the frequency on the fly is something new in Linux, so we need to carefully flag the drivers which do and do not support it. A controller capability is created for that, and the presence for this capability will always be checked before accepting such pattern. Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org> Link: https://patch.msgid.link/20241224-winbond-6-11-rc1-quad-support-v2-2-ad218dbc406f@bootlin.com Signed-off-by: Mark Brown <broonie@kernel.org> Stable-dep-of: 40ad64ac25bb ("spi: nxp-fspi: Propagate fwnode in ACPI case as well") 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.