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There is no point in having the commit19b61392c5("spi: spi-dw: Add lock protect dw_spi rx/tx to prevent concurrent calls") applied. The commit author made an assumption that the problem with the rx data mismatch was due to the lack of the data protection. While most likely it was caused by the lack of the memory barrier. So having the commitbfda044533("spi: dw: use "smp_mb()" to avoid sending spi data error") applied would be enough to fix the problem. Indeed the spin unlock operation makes sure each memory operation issued before the release will be completed before it's completed. In other words it works as an implicit one way memory barrier. So having both smp_mb() and the spin_unlock_irqrestore() here is just redundant. One of them would be enough. It's better to leave the smp_mb() since the Tx/Rx buffers consistency is provided by the data transfer algorithm implementation: first we initialize the buffers pointers, then make sure the assignments are visible by the other CPUs by calling the smp_mb(), only after that enable the interrupt, which handler uses the buffers. Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru> Link: https://lore.kernel.org/r/20200920112914.26501-5-Sergey.Semin@baikalelectronics.ru Signed-off-by: Mark Brown <broonie@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.