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[ Upstream commit9f34baf67e] n_bytes variable in the driver represents the number of bytes per word that needs to be sent/copied to fifo. Bits/word can be between 8 and 32 bits from the client but in memory they are a power of 2, same is mentioned in spi.h header: " * @bits_per_word: Data transfers involve one or more words; word sizes * like eight or 12 bits are common. In-memory wordsizes are * powers of two bytes (e.g. 20 bit samples use 32 bits). * This may be changed by the device's driver, or left at the * default (0) indicating protocol words are eight bit bytes. * The spi_transfer.bits_per_word can override this for each transfer. " Hence, round of n_bytes to a power of 2 to avoid values like 3 which would generate unalligned/odd accesses to memory/fifo. * tested on Baikal-T1 based system with DW SPI-looped back interface transferring a chunk of data with DFS:8,12,16. Fixes:a51acc2400("spi: dw: Add support for 32-bits max xfer size") Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com Signed-off-by: Joy Chakraborty <joychakr@google.com Reviewed-by: Serge Semin <fancer.lancer@gmail.com Tested-by: Serge Semin <fancer.lancer@gmail.com Link: https://lore.kernel.org/r/20230512104746.1797865-4-joychakr@google.com Signed-off-by: Mark Brown <broonie@kernel.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.