amd_freq_sensitivity.c
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/*
* amd_freq_sensitivity.c: AMD frequency sensitivity feedback powersave bias
* for the ondemand governor.
*
* Copyright (C) 2013 Advanced Micro Devices, Inc.
*
* Author: Jacob Shin <jacob.shin@amd.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/percpu-defs.h>
#include <linux/init.h>
#include <linux/mod_devicetable.h>
#include <asm/msr.h>
#include <asm/cpufeature.h>
#include "cpufreq_governor.h"
#define MSR_AMD64_FREQ_SENSITIVITY_ACTUAL 0xc0010080
#define MSR_AMD64_FREQ_SENSITIVITY_REFERENCE 0xc0010081
#define CLASS_CODE_SHIFT 56
#define POWERSAVE_BIAS_MAX 1000
#define POWERSAVE_BIAS_DEF 400
struct cpu_data_t {
u64 actual;
u64 reference;
unsigned int freq_prev;
};
static DEFINE_PER_CPU(struct cpu_data_t, cpu_data);
static unsigned int amd_powersave_bias_target(struct cpufreq_policy *policy,
unsigned int freq_next,
unsigned int relation)
{
int sensitivity;
long d_actual, d_reference;
struct msr actual, reference;
struct cpu_data_t *data = &per_cpu(cpu_data, policy->cpu);
struct dbs_data *od_data = policy->governor_data;
struct od_dbs_tuners *od_tuners = od_data->tuners;
struct od_cpu_dbs_info_s *od_info =
od_data->cdata->get_cpu_dbs_info_s(policy->cpu);
if (!od_info->freq_table)
return freq_next;
rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_ACTUAL,
&actual.l, &actual.h);
rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_REFERENCE,
&reference.l, &reference.h);
actual.h &= 0x00ffffff;
reference.h &= 0x00ffffff;
/* counter wrapped around, so stay on current frequency */
if (actual.q < data->actual || reference.q < data->reference) {
freq_next = policy->cur;
goto out;
}
d_actual = actual.q - data->actual;
d_reference = reference.q - data->reference;
/* divide by 0, so stay on current frequency as well */
if (d_reference == 0) {
freq_next = policy->cur;
goto out;
}
sensitivity = POWERSAVE_BIAS_MAX -
(POWERSAVE_BIAS_MAX * (d_reference - d_actual) / d_reference);
clamp(sensitivity, 0, POWERSAVE_BIAS_MAX);
/* this workload is not CPU bound, so choose a lower freq */
if (sensitivity < od_tuners->powersave_bias) {
if (data->freq_prev == policy->cur)
freq_next = policy->cur;
if (freq_next > policy->cur)
freq_next = policy->cur;
else if (freq_next < policy->cur)
freq_next = policy->min;
else {
unsigned int index;
cpufreq_frequency_table_target(policy,
od_info->freq_table, policy->cur - 1,
CPUFREQ_RELATION_H, &index);
freq_next = od_info->freq_table[index].frequency;
}
data->freq_prev = freq_next;
} else
data->freq_prev = 0;
out:
data->actual = actual.q;
data->reference = reference.q;
return freq_next;
}
static int __init amd_freq_sensitivity_init(void)
{
u64 val;
if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
return -ENODEV;
if (!static_cpu_has(X86_FEATURE_PROC_FEEDBACK))
return -ENODEV;
if (rdmsrl_safe(MSR_AMD64_FREQ_SENSITIVITY_ACTUAL, &val))
return -ENODEV;
if (!(val >> CLASS_CODE_SHIFT))
return -ENODEV;
od_register_powersave_bias_handler(amd_powersave_bias_target,
POWERSAVE_BIAS_DEF);
return 0;
}
late_initcall(amd_freq_sensitivity_init);
static void __exit amd_freq_sensitivity_exit(void)
{
od_unregister_powersave_bias_handler();
}
module_exit(amd_freq_sensitivity_exit);
static const struct x86_cpu_id amd_freq_sensitivity_ids[] = {
X86_FEATURE_MATCH(X86_FEATURE_PROC_FEEDBACK),
{}
};
MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);
MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
"the ondemand governor.");
MODULE_LICENSE("GPL");