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The CSI IP found inside the Renesas RZ/V2M SoC supports both SPI host and SPI target roles. When working in target mode, the CSI IP has the option of using its Slave Selection (SS) pin to enable TX and RX operations. Since the SPI target cannot control the clock, when working as target it's best not to stop operations during a transfer, as by doing so the IP will not send or receive data, regardless of clock and active level on pin SS. A side effect from not stopping operations is that the RX FIFO needs to be flushed, word by word, when RX data needs to be discarded. Finally, when in target mode timings are tighter, as missing a deadline translates to errors being thrown, resulting in aborting the transfer. In order to speed things up, we can avoid waiting for the TX FIFO to be empty, we can just wait for the RX FIFO to contain at least the number of words that we expect. Add target support to the currently existing CSI driver. Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com> Link: https://lore.kernel.org/r/20230927162508.328736-3-fabrizio.castro.jz@renesas.com Signed-off-by: Mark Brown <broonie@kernel.org> |
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| README | ||
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.