path: root/drivers/cpufreq/amd-pstate.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * amd-pstate.c - AMD Processor P-state Frequency Driver
 *
 * Copyright (C) 2021 Advanced Micro Devices, Inc. All Rights Reserved.
 *
 * Author: Huang Rui <ray.huang@amd.com>
 *
 * AMD P-State introduces a new CPU performance scaling design for AMD
 * processors using the ACPI Collaborative Performance and Power Control (CPPC)
 * feature which works with the AMD SMU firmware providing a finer grained
 * frequency control range. It is to replace the legacy ACPI P-States control,
 * allows a flexible, low-latency interface for the Linux kernel to directly
 * communicate the performance hints to hardware.
 *
 * AMD P-State is supported on recent AMD Zen base CPU series include some of
 * Zen2 and Zen3 processors. _CPC needs to be present in the ACPI tables of AMD
 * P-State supported system. And there are two types of hardware implementations
 * for AMD P-State: 1) Full MSR Solution and 2) Shared Memory Solution.
 * X86_FEATURE_CPPC CPU feature flag is used to distinguish the different types.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/sched.h>
#include <linux/cpufreq.h>
#include <linux/compiler.h>
#include <linux/dmi.h>
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <linux/uaccess.h>
#include <linux/static_call.h>
#include <linux/amd-pstate.h>

#include <acpi/processor.h>
#include <acpi/cppc_acpi.h>

#include <asm/msr.h>
#include <asm/processor.h>
#include <asm/cpufeature.h>
#include <asm/cpu_device_id.h>
#include "amd-pstate-trace.h"

#define AMD_PSTATE_TRANSITION_LATENCY	20000
#define AMD_PSTATE_TRANSITION_DELAY	1000

/*
 * TODO: We need more time to fine tune processors with shared memory solution
 * with community together.
 *
 * There are some performance drops on the CPU benchmarks which reports from
 * Suse. We are co-working with them to fine tune the shared memory solution. So
 * we disable it by default to go acpi-cpufreq on these processors and add a
 * module parameter to be able to enable it manually for debugging.
 */
static struct cpufreq_driver *current_pstate_driver;
static struct cpufreq_driver amd_pstate_driver;
static