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e4832d190b
Add new SoC dtsi file for the RK3566T variant of the Rockchip RK3566 SoC.
The difference between the RK3566T variant and the "full-fat" RK3566 variant
is in fewer supported CPU and GPU OPPs on the RK3566T, and in the absence of
a functional NPU, which we currently don't have to worry about.
Examples of the boards based on the RK3566T include the Pine64 Quartz64 Zero
SBC, [1] which is yet to be supported, the Radxa ROCK 3C, and the Radxa ZERO
3E/3W SBCs, which are both already supported. Though, Radxa doesn't mention
the use of RK3566T officially, but its official SBC specifications do state
that the maximum frequency for the Cortex-A55 cores on those SBCs is lower
than the "full-fat" RK3566's 1.8 GHz, which makes spotting the presence of
the RK3566T SoC variant rather easy. [2][3][4] An additional, helpful cue
is that Radxa handles the CPU and GPU OPPs for the RK3566T variant separately
in its downstream kernel source. [5]
The CPU and GPU OPPs supported on the RK3566T SoC variant are taken from the
vendor kernel source, [6] which uses the values of the "opp-supported-hw" OPP
properties to determine which ones are supported on a particular SoC variant.
The actual values of the "opp-supported-hw" properties make it rather easy
to see what OPPs are supported on the RK3566T SoC variant, but that, rather
unfortunately, clashes with the maximum frequencies advertised officially
for the Cortex-A55 CPU cores on the above-mentioned SBCs. [1][2][3][4] The
vendor kernel source indicates that the maximum frequency for the CPU cores
is 1.4 GHz, while the SBC specifications state that to be 1.6 GHz. Until
that discrepancy is resolved somehow, let's take the safe approach and use
the lower maximum frequency for the CPU cores.
Update the dts files of the currently supported RK3566T-based boards to use
the new SoC dtsi for the RK3566T variant. This actually takes the CPU cores
and the GPUs found on these boards out of their earlier overclocks, but it
also means that the officially advertised specifications [1][2][3][4] of the
highest supported frequencies for the Cortex-A55 CPU cores on these boards
may actually be wrong, as already explained above.
The correctness of the introduced changes was validated by decompiling and
comparing all affected board dtb files before and after these changes.
[1] https://wiki.pine64.org/wiki/Quartz64
[2] https://dl.radxa.com/rock3/docs/hw/3c/radxa_rock3c_product_brief.pdf
[3] https://dl.radxa.com/zero3/docs/hw/3e/radxa_zero_3e_product_brief.pdf
[4] https://dl.radxa.com/zero3/docs/hw/3w/radxa_zero_3w_product_brief.pdf
[5]
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| Documentation | ||
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| include | ||
| init | ||
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| ipc | ||
| kernel | ||
| lib | ||
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| net | ||
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| scripts | ||
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| tools | ||
| usr | ||
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| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
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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 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.