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Indeed the registers content doesn't get cleared when the SPI controller is disabled and enabled. Max burst lengths aren't changed since the Rx and Tx DMA channels are requested on init stage and are kept acquired until the device is removed. Obviously SPI controller FIFO depth can't be changed. Due to all of that we can safely move the DMA Transmit and Receive data level registers initialization to the SPI controller DMA init stage (when the SPI controller is being probed) instead of doing it for each SPI transfer when dma_setup is called. This shall speed the DMA-based SPI transfer initialization up a bit, particularly if the APB bus is relatively slow. Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru> Link: https://lore.kernel.org/r/20200920112322.24585-2-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.