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cpufreq: amd-pstate: Introduce a new AMD P-State driver to support fu…
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…ture processors

AMD P-State is the AMD CPU performance scaling driver that introduces a
new CPU frequency control mechanism on AMD Zen based CPU series in Linux
kernel. The new mechanism is based on Collaborative processor
performance control (CPPC) which is finer grain frequency management
than legacy ACPI hardware P-States. Current AMD CPU platforms are using
the ACPI P-states driver to manage CPU frequency and clocks with
switching only in 3 P-states. AMD P-State is to replace the ACPI
P-states controls, allows a flexible, low-latency interface for the
Linux kernel to directly communicate the performance hints to hardware.

AMD P-State leverages the Linux kernel governors such as *schedutil*,
*ondemand*, etc. to manage the performance hints which are provided by CPPC
hardware functionality. The first version for AMD P-State is to support one
of the Zen3 processors, and we will support more in future after we verify
the hardware and SBIOS functionalities.

There are two types of hardware implementations for AMD P-State: one is full
MSR support and another is shared memory support. It can use
X86_FEATURE_CPPC feature flag to distinguish the different types.

Using the new AMD P-State method + kernel governors (*schedutil*,
*ondemand*, ...) to manage the frequency update is the most appropriate
bridge between AMD Zen based hardware processor and Linux kernel, the
processor is able to adjust to the most efficiency frequency according to
the kernel scheduler loading.

Please check the detailed CPU feature and MSR register description in
Processor Programming Reference (PPR) for AMD Family 19h Model 51h,
Revision A1 Processors:

https://www.amd.com/system/files/TechDocs/56569-A1-PUB.zip

Signed-off-by: Huang Rui <ray.huang@amd.com>
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huangrui authored and xanmod committed Jan 12, 2022
1 parent 4da27c1 commit 6a3addf
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17 changes: 17 additions & 0 deletions drivers/cpufreq/Kconfig.x86
Expand Up @@ -34,6 +34,23 @@ config X86_PCC_CPUFREQ

If in doubt, say N.

config X86_AMD_PSTATE
tristate "AMD Processor P-State driver"
depends on X86
select ACPI_PROCESSOR if ACPI
select ACPI_CPPC_LIB if X86_64 && ACPI
select CPU_FREQ_GOV_SCHEDUTIL if SMP
help
This driver adds a CPUFreq driver which utilizes a fine grain
processor performance frequency control range instead of legacy
performance levels. _CPC needs to be present in the ACPI tables
of the system.

For details, take a look at:
<file:Documentation/admin-guide/pm/amd-pstate.rst>.

If in doubt, say N.

config X86_ACPI_CPUFREQ
tristate "ACPI Processor P-States driver"
depends on ACPI_PROCESSOR
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1 change: 1 addition & 0 deletions drivers/cpufreq/Makefile
Expand Up @@ -25,6 +25,7 @@ obj-$(CONFIG_CPUFREQ_DT_PLATDEV) += cpufreq-dt-platdev.o
# speedstep-* is preferred over p4-clockmod.

obj-$(CONFIG_X86_ACPI_CPUFREQ) += acpi-cpufreq.o
obj-$(CONFIG_X86_AMD_PSTATE) += amd-pstate.o
obj-$(CONFIG_X86_POWERNOW_K8) += powernow-k8.o
obj-$(CONFIG_X86_PCC_CPUFREQ) += pcc-cpufreq.o
obj-$(CONFIG_X86_POWERNOW_K6) += powernow-k6.o
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