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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>
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.