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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>
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