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This reverts commit13d515c796(spi: omap2-mcspi: Switch to readl_poll_timeout()). The amount of time spent polling for the MCSPI_CHSTAT bits to be set on AM335x-icev2 platform is less than 1us (about 0.6us) in most cases, with or without using DMA. So, in most cases the function need not sleep. Also, setting the sleep_usecs to zero would not be optimal here because ktime_add_us() used in readl_poll_timeout() is slower compared to the direct addition used after the revert. So, it is sub-optimal to use readl_poll_timeout in this case. When DMA is not enabled, this revert results in an increase of about 27% in throughput and decrease of about 20% in CPU usage. However, the CPU usage and throughput are almost the same when used with DMA. Therefore, fix this by reverting the commit which switched to using readl_poll_timeout(). Fixes:13d515c796("spi: omap2-mcspi: Switch to readl_poll_timeout()") Signed-off-by: Aswath Govindraju <a-govindraju@ti.com> Link: https://lore.kernel.org/r/20200910122624.8769-1-a-govindraju@ti.com 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.