intel_pstate.c

/*
 * intel_pstate.c: Native P state management for Intel processors
 *
 * (C) Copyright 2012 Intel Corporation
 * Author: Dirk Brandewie <dirk.j.brandewie@intel.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2
 * of the License.
 */

#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/ktime.h>
#include <linux/hrtimer.h>
#include <linux/tick.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/list.h>
#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/sysfs.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/acpi.h>
#include <trace/events/power.h>

#include <asm/div64.h>
#include <asm/msr.h>
#include <asm/cpu_device_id.h>

#define SAMPLE_COUNT		3

#define BYT_RATIOS		0x66a
#define BYT_VIDS		0x66b
#define BYT_TURBO_RATIOS	0x66c


#define FRAC_BITS 6
#define int_tofp(X) ((int64_t)(X) << FRAC_BITS)
#define fp_toint(X) ((X) >> FRAC_BITS)
#define FP_ROUNDUP(X) ((X) += 1 << FRAC_BITS)

static inline int32_t mul_fp(int32_t x, int32_t y)
{
	return ((int64_t)x * (int64_t)y) >> FRAC_BITS;
}

static inline int32_t div_fp(int32_t x, int32_t y)
{
	return div_s64((int64_t)x << FRAC_BITS, (int64_t)y);
}

struct sample {
	int32_t core_pct_busy;
	u64 aperf;
	u64 mperf;
	unsigned long long tsc;
	int freq;
};

struct pstate_data {
	int	current_pstate;
	int	min_pstate;
	int	max_pstate;
	int	turbo_pstate;
};

struct vid_data {
	int32_t min;
	int32_t max;
	int32_t ratio;
};

struct _pid {
	int setpoint;
	int32_t integral;
	int32_t p_gain;
	int32_t i_gain;
	int32_t d_gain;
	int deadband;
	int32_t last_err;
};

struct cpudata {
	int cpu;

	char name[64];

	struct timer_list timer;

	struct pstate_data pstate;
	struct vid_data vid;
	struct _pid pid;

	u64	prev_aperf;
	u64	prev_mperf;
	unsigned long long prev_tsc;
	int	sample_ptr;
	struct sample samples[SAMPLE_COUNT];
};

static struct cpudata **all_cpu_data;
struct pstate_adjust_policy {
	int sample_rate_ms;
	int deadband;
	int setpoint;
	int p_gain_pct;
	int d_gain_pct;
	int i_gain_pct;
};

struct pstate_funcs {
	int (*get_max)(void);
	int (*get_min)(void);
	int (*get_turbo)(void);
	void (*set)(struct cpudata*, int pstate);
	void (*get_vid)(struct cpudata *);
};

struct cpu_defaults {
	struct pstate_adjust_policy pid_policy;
	struct pstate_funcs funcs;
};

static struct pstate_adjust_policy pid_params;
static struct pstate_funcs pstate_funcs;

struct perf_limits {
	int no_turbo;
	int max_perf_pct;
	int min_perf_pct;
	int32_t max_perf;
	int32_t min_perf;
	int max_policy_pct;
	int max_sysfs_pct;
};

static struct perf_limits limits = {
	.no_turbo = 0,
	.max_perf_pct = 100,
	.max_perf = int_tofp(1),
	.min_perf_pct = 0,
	.min_perf = 0,
	.max_policy_pct = 100,
	.max_sysfs_pct = 100,
};

static inline void pid_reset(struct _pid *pid, int setpoint, int busy,
			int deadband, int integral) {
	pid->setpoint = setpoint;
	pid->deadband  = deadband;
	pid->integral  = int_tofp(integral);
	pid->last_err  = setpoint - busy;
}

static inline void pid_p_gain_set(struct _pid *pid, int percent)
{
	pid->p_gain = div_fp(int_tofp(percent), int_tofp(100));
}

static inline void pid_i_gain_set(struct _pid *pid, int percent)
{
	pid->i_gain = div_fp(int_tofp(percent), int_tofp(100));
}

static inline void pid_d_gain_set(struct _pid *pid, int percent)
{

	pid->d_gain = div_fp(int_tofp(percent), int_tofp(100));
}

static signed int pid_calc(struct _pid *pid, int32_t busy)
{
	signed int result;
	int32_t pterm, dterm, fp_error;
	int32_t integral_limit;

	fp_error = int_tofp(pid->setpoint) - busy;

	if (abs(fp_error) <= int_tofp(pid->deadband))
		return 0;

	pterm = mul_fp(pid->p_gain, fp_error);

	pid->integral += fp_error;

	/* limit the integral term */
	integral_limit = int_tofp(30);
	if (pid->integral > integral_limit)
		pid->integral = integral_limit;
	if (pid->integral < -integral_limit)
		pid->integral = -integral_limit;

	dterm = mul_fp(pid->d_gain, fp_error - pid->last_err);
	pid->last_err = fp_error;