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Split spi transfers into chunks of <=65532 to enable the driver to perform DMA transfer on big buffers. The DLEN register specifies the number of bytes to transfer in DMA mode. It is 16-bit wide and thus the maximum DMA transfer is 65535 bytes. Set the maximum to 65532 (4 byte aligned) since the FIFO in DMA mode is accessed in 4 byte chunks. ->max_dma_len is the value the spi core uses when splitting the buffer into scatter gather entries. The BCM2835 DMA block has 2 types of channels/engines: - Normal: Max length: 1G - Lite: Max length: 65535 Even when using a Lite channel we will not exceed the max length, so let's drop setting ->max_dma_len. Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> Reviewed-by: Lukas Wunner <lukas@wunner.de> 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.