Serge Semin 7e31cea7d1 spi: dw: Use relaxed IO-methods to access FIFOs
In accordance with [1] the relaxed methods are guaranteed to be ordered
with respect to other accesses from the same CPU thread to the same
peripheral.  This is what we need during the data read/write from/to the
controller FIFOs being executed within a single IRQ handler or a kernel
task.

Such optimization shall significantly speed the data reader and writer up.
For instance, the relaxed IO-accessors utilization on Baikal-T1 lets the
driver to support the SPI memory operations with bus frequency three-fold
faster than if normal IO-accessors would be used.

[1] "LINUX KERNEL MEMORY BARRIERS", Documentation/memory-barriers.txt,
    Section "KERNEL I/O BARRIER EFFECTS"

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112914.26501-8-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
2020-09-29 17:22:24 +01:00
2020-09-06 17:11:40 -07:00

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.
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