linux/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 <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>

#define AMD_PSTATE_TRANSITION_LATENCY	0x20000
#define AMD_PSTATE_TRANSITION_DELAY	500

static struct cpufreq_driver amd_pstate_driver;

/**
 * struct amd_cpudata - private CPU data for AMD P-State
 * @cpu: CPU number
 * @cppc_req_cached: cached performance request hints
 * @highest_perf: the maximum performance an individual processor may reach,
 *		  assuming ideal conditions
 * @nominal_perf: the maximum sustained performance level of the processor,
 *		  assuming ideal operating conditions
 * @lowest_nonlinear_perf: the lowest performance level at which nonlinear power
 *			   savings are achieved
 * @lowest_perf: the absolute lowest performance level of the processor
 * @max_freq: the frequency that mapped to highest_perf
 * @min_freq: the frequency that mapped to lowest_perf
 * @nominal_freq: the frequency that mapped to nominal_perf
 * @lowest_nonlinear_freq: the frequency that mapped to lowest_nonlinear_perf
 *
 * The amd_cpudata is key private data for each CPU thread in AMD P-State, and
 * represents all the attributes and goals that AMD P-State requests at runtime.
 */
struct amd_cpudata {
	int	cpu;

	u64	cppc_req_cached;

	u32	highest_perf;
	u32	nominal_perf;
	u32	lowest_nonlinear_perf;
	u32	lowest_perf;

	u32	max_freq;
	u32	min_freq;
	u32	nominal_freq;
	u32	lowest_nonlinear_freq;
};

static inline int amd_pstate_enable(bool enable)
{
	return wrmsrl_safe(MSR_AMD_CPPC_ENABLE, enable);
}

static int amd_pstate_init_perf(struct amd_cpudata *cpudata)
{
	u64 cap1;

	int ret = rdmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1,
				     &cap1);
	if (ret)
		return ret;

	/*
	 * TODO: Introduce AMD specific power feature.
	 *
	 * CPPC entry doesn't indicate the highest performance in some ASICs.
	 */
	WRITE_ONCE(cpudata->highest_perf, amd_get_highest_perf());

	WRITE_ONCE(cpudata->nominal_perf, AMD_CPPC_NOMINAL_PERF(cap1));
	WRITE_ONCE(cpudata->lowest_nonlinear_perf, AMD_CPPC_LOWNONLIN_PERF(cap1));
	WRITE_ONCE(cpudata->lowest_perf, AMD_CPPC_LOWEST_PERF(cap1));

	return 0;
}

static void amd_pstate_update_perf(struct amd_cpudata *cpudata, u32 min_perf,
				   u32 des_perf, u32 max_perf, bool fast_switch)
{
	if (fast_switch)
		wrmsrl(MSR_AMD_CPPC_REQ, READ_ONCE(cpudata->cppc_req_cached));
	else
		wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ,
			      READ_ONCE(cpudata->cppc_req_cached));
}

static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
			      u32 des_perf, u32 max_perf, bool fast_switch)
{
	u64 prev = READ_ONCE(cpudata->cppc_req_cached);
	u64 value = prev;

	value &= ~AMD_CPPC_MIN_PERF(~0L);
	value |= AMD_CPPC_MIN_PERF(min_perf);

	value &= ~AMD_CPPC_DES_PERF(~0L);
	value |= AMD_CPPC_DES_PERF(des_perf);

	value &= ~AMD_CPPC_MAX_PERF(~0L);
	value |= AMD_CPPC_MAX_PERF(max_perf);

	if (value == prev)
		return;

	WRITE_ONCE(cpudata->cppc_req_cached, value);

	amd_pstate_update_perf(cpudata, min_perf, des_perf,
			       max_perf, fast_switch);
}

static int amd_pstate_verify(struct cpufreq_policy_data *policy)
{
	cpufreq_verify_within_cpu_limits(policy);

	return 0;
}

static int amd_pstate_target(struct cpufreq_policy *policy,
			     unsigned int target_freq,
			     unsigned int relation)
{
	struct cpufreq_freqs freqs;
	struct amd_cpudata *cpudata = policy->driver_data;
	unsigned long max_perf, min_perf, des_perf, cap_perf;

	if (!cpudata->max_freq)
		return -ENODEV;

	cap_perf = READ_ONCE(cpudata->highest_perf);
	min_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);
	max_perf = cap_perf;

	freqs.old = policy->cur;
	freqs.new = target_freq;

	des_perf = DIV_ROUND_CLOSEST(target_freq * cap_perf,
				     cpudata->max_freq);

	cpufreq_freq_transition_begin(policy, &freqs);
	amd_pstate_update(cpudata, min_perf, des_perf,
			  max_perf, false);
	cpufreq_freq_transition_end(policy, &freqs, false);

	return 0;
}

static int amd_get_min_freq(struct amd_cpudata *cpudata)
{
	struct cppc_perf_caps cppc_perf;

	int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
	if (ret)
		return ret;

	/* Switch to khz */
	return cppc_perf.lowest_freq * 1000;
}

static int amd_get_max_freq(struct amd_cpudata *cpudata)
{
	struct cppc_perf_caps cppc_perf;
	u32 max_perf, max_freq, nominal_freq, nominal_perf;
	u64 boost_ratio;

	int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
	if (ret)
		return ret;

	nominal_freq = cppc_perf.nominal_freq;
	nominal_perf = READ_ONCE(cpudata->nominal_perf);
	max_perf = READ_ONCE(cpudata->highest_perf);

	boost_ratio = div_u64(max_perf << SCHED_CAPACITY_SHIFT,
			      nominal_perf);

	max_freq = nominal_freq * boost_ratio >> SCHED_CAPACITY_SHIFT;

	/* Switch to khz */
	return max_freq * 1000;
}

static int amd_get_nominal_freq(struct amd_cpudata *cpudata)
{
	struct cppc_perf_caps cppc_perf;

	int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
	if (ret)
		return ret;

	/* Switch to khz */
	return cppc_perf.nominal_freq * 1000;
}

static int amd_get_lowest_nonlinear_freq(struct amd_cpudata *cpudata)
{
	struct cppc_perf_caps cppc_perf;
	u32 lowest_nonlinear_freq, lowest_nonlinear_perf,
	    nominal_freq, nominal_perf;
	u64 lowest_nonlinear_ratio;

	int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
	if (ret)
		return ret;

	nominal_freq = cppc_perf.nominal_freq;
	nominal_perf = READ_ONCE(cpudata->nominal_perf);

	lowest_nonlinear_perf = cppc_perf.lowest_nonlinear_perf;

	lowest_nonlinear_ratio = div_u64(lowest_nonlinear_perf << SCHED_CAPACITY_SHIFT,
					 nominal_perf);

	lowest_nonlinear_freq = nominal_freq * lowest_nonlinear_ratio >> SCHED_CAPACITY_SHIFT;

	/* Switch to khz */
	return lowest_nonlinear_freq * 1000;
}

static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
{
	int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;
	struct device *dev;
	struct amd_cpudata *cpudata;

	dev = get_cpu_device(policy->cpu);
	if (!dev)
		return -ENODEV;

	cpudata = kzalloc(sizeof(*cpudata), GFP_KERNEL);
	if (!cpudata)
		return -ENOMEM;

	cpudata->cpu = policy->cpu;

	ret = amd_pstate_init_perf(cpudata);
	if (ret)
		goto free_cpudata;

	min_freq = amd_get_min_freq(cpudata);
	max_freq = amd_get_max_freq(cpudata);
	nominal_freq = amd_get_nominal_freq(cpudata);
	lowest_nonlinear_freq = amd_get_lowest_nonlinear_freq(cpudata);

	if (min_freq < 0 || max_freq < 0 || min_freq > max_freq) {
		dev_err(dev, "min_freq(%d) or max_freq(%d) value is incorrect\n",
			min_freq, max_freq);
		ret = -EINVAL;
		goto free_cpudata;
	}

	policy->cpuinfo.transition_latency = AMD_PSTATE_TRANSITION_LATENCY;
	policy->transition_delay_us = AMD_PSTATE_TRANSITION_DELAY;

	policy->min = min_freq;
	policy->max = max_freq;

	policy->cpuinfo.min_freq = min_freq;
	policy->cpuinfo.max_freq = max_freq;

	/* It will be updated by governor */
	policy->cur = policy->cpuinfo.min_freq;

	/* Initial processor data capability frequencies */
	cpudata->max_freq = max_freq;
	cpudata->min_freq = min_freq;
	cpudata->nominal_freq = nominal_freq;
	cpudata->lowest_nonlinear_freq = lowest_nonlinear_freq;

	policy->driver_data = cpudata;

	return 0;

free_cpudata:
	kfree(cpudata);
	return ret;
}

static int amd_pstate_cpu_exit(struct cpufreq_policy *policy)
{
	struct amd_cpudata *cpudata;

	cpudata = policy->driver_data;

	kfree(cpudata);

	return 0;
}

static struct cpufreq_driver amd_pstate_driver = {
	.flags		= CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
	.verify		= amd_pstate_verify,
	.target		= amd_pstate_target,
	.init		= amd_pstate_cpu_init,
	.exit		= amd_pstate_cpu_exit,
	.name		= "amd-pstate",
};

static int __init amd_pstate_init(void)
{
	int ret;

	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
		return -ENODEV;

	if (!acpi_cpc_valid()) {
		pr_debug("the _CPC object is not present in SBIOS\n");
		return -ENODEV;
	}

	/* don't keep reloading if cpufreq_driver exists */
	if (cpufreq_get_current_driver())
		return -EEXIST;

	/* capability check */
	if (!boot_cpu_has(X86_FEATURE_CPPC)) {
		pr_debug("AMD CPPC MSR based functionality is not supported\n");
		return -ENODEV;
	}

	/* enable amd pstate feature */
	ret = amd_pstate_enable(true);
	if (ret) {
		pr_err("failed to enable amd-pstate with return %d\n", ret);
		return ret;
	}

	ret = cpufreq_register_driver(&amd_pstate_driver);
	if (ret)
		pr_err("failed to register amd_pstate_driver with return %d\n",
		       ret);

	return ret;
}

static void __exit amd_pstate_exit(void)
{
	cpufreq_unregister_driver(&amd_pstate_driver);

	amd_pstate_enable(false);
}

module_init(amd_pstate_init);
module_exit(amd_pstate_exit);

MODULE_AUTHOR("Huang Rui <ray.huang@amd.com>");
MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");
MODULE_LICENSE("GPL");