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Compared to the previously supported RZ/V2H, the Renesas RZ/T2H (R9A09G077) and RZ/N2H (R9A09G087) SoCs have a smaller FIFO, no resets, and only two clocks: PCLKSPIn and PCLK. PCLKSPIn, being the clock from which the SPI transfer clock is generated, is the equivalent of the TCLK clock from RZ/V2H. They also support generating the SPI transfer clock from PCLK. PCLKSPIn supports multiple dividers, generating multiple possible frequencies from its parent. To handle this, do the following changes. Use the minimum frequency of SPI clock to calculate the SPI controller's min_speed_hz, and the maximum frequency to calculate max_speed_hz. Add a new function, rzv2h_rspi_find_rate_variable(), which is used for the .find_tclk_rate() callback, and which supports handling clocks with a variable rate, with the following overall logic. Iterate through all possible BRDV values. For each BRDV, calculate two different SPRs, one for the clock's minimum frequency, and one for the maxmimum, and iterate through each SPR between them. If the minimum SPR is higher than the upper SPR limit, the minimum rate is too high to achieve the requested SPI frequency, skip to the next BRDV. For each SPR, calculate a rate and let the clock framework round it to the closest supported rate of the clock. The rate and SPR that generate a transfer frequency closest to the requested SPI transfer frequency will be picked. Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com> Link: https://patch.msgid.link/20251119161434.595677-12-cosmin-gabriel.tanislav.xa@renesas.com Signed-off-by: Mark Brown <broonie@kernel.org> |
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| arch | ||
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| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
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| net | ||
| rust | ||
| samples | ||
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| README | ||
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 reStructuredText 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.