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These controllers are based on the DW APB SSI IP-core and embedded into the SoC, so two of them are equipped with IRQ, DMA, 64 words FIFOs and 4 native CS, while another one as being utilized by the Baikal-T1 System Boot Controller has got a very limited resources: no IRQ, no DMA, only a single native chip-select and just 8 bytes Tx/Rx FIFOs available. That's why we have to mark the IRQ to be optional for the later interface. The SPI controller embedded into the Baikal-T1 System Boot Controller can be also used to directly access an external SPI flash by means of a dedicated FSM. The corresponding MMIO region availability is switchable by the embedded multiplexor, which phandle can be specified in the dts node. * We added a new example to test out the non-standard Baikal-T1 System Boot SPI Controller DT binding. Co-developed-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru> Signed-off-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru> Reviewed-by: Rob Herring <robh@kernel.org> Link: https://lore.kernel.org/r/20201007235511.4935-21-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.