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Huacai Chen ccf5145414 cpufreq: Add Loongson-3 CPUFreq driver support
Some of LoongArch processors (Loongson-3 series) support DVFS, their
IOCSR.FEATURES has IOCSRF_FREQSCALE set. And they has a micro-core in
the package called SMC (System Management Controller), which can be
used to detect temperature, control fans, scale frequency and voltage,
etc.

The Loongson-3 CPUFreq driver is very simple now, it communicate with
SMC, get DVFS info, set target frequency from CPUFreq core, and so on.

There is a command list to interact with SMC, widely-used commands in
the CPUFreq driver include:

CMD_GET_VERSION: Get SMC firmware version.

CMD_GET_FEATURE: Get enabled SMC features.

CMD_SET_FEATURE: Enable SMC features, such as basic DVFS, BOOST.

CMD_GET_FREQ_LEVEL_NUM: Get the number of all frequency levels.

CMD_GET_FREQ_BOOST_LEVEL: Get the first boost frequency level.

CMD_GET_FREQ_LEVEL_INFO: Get the detail info of a frequency level.

CMD_GET_FREQ_INFO: Get the current frequency.

CMD_SET_FREQ_INFO: Set the target frequency.

In future we will add automatic frequency scaling, which is similar to
Intel's HWP (HardWare P-State).

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
[ Viresh: Minor formatting cleanups, change return type of exit() to
	  void and use devm_mutex_init() ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
History 2024-07-09 08:45:43 +05:30
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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.