Message-Id: <1354734091-29870-2-git-send-email-dirk.brandewie@gmail.com>
Date:	Wed,  5 Dec 2012 11:01:31 -0800
From:	dirk.brandewie@...il.com
To:	linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org,
	linux-pm@...r.kernel.org
Cc:	rjw@...k.pl, deneen.t.dock@...el.com, arjan@...ux.intel.com,
	Dirk Brandewie <dirk.brandewie@...il.com>
Subject: [PATCH RFC 1/1] cpufreq/x86: Add P-state driver for sandy bridge.

From: Dirk Brandewie <dirk.brandewie@...il.com>

Add a P-state driver for the Sandy bridge processor.

This driver provides better power efficiency than the current
governors of the Intel architecture.  The driver masquerades as a
frequency governor to the cpufreq subsystem but does not use cpufreq
to change frequency.

Issues:
  does not report current frequency via cpufreq subsystem so this
  confuses some tools.


Signed-off-by: Dirk Brandewie <dirk.brandewie@...il.com>
---
 drivers/cpufreq/Kconfig.x86   |    8 +
 drivers/cpufreq/Makefile      |    1 +
 drivers/cpufreq/cpufreq_snb.c |  727 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 736 insertions(+), 0 deletions(-)
 create mode 100644 drivers/cpufreq/cpufreq_snb.c

diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86
index 934854a..8c8acd3 100644
--- a/drivers/cpufreq/Kconfig.x86
+++ b/drivers/cpufreq/Kconfig.x86
@@ -2,6 +2,14 @@
 # x86 CPU Frequency scaling drivers
 #
 
+config X86_SNB_CPUFREQ
+       tristate "SandyBridge frequency Governor"
+       help
+         This driver will override the CPU_FREQ subsystem when
+	 the system has a SandyBridge processor
+
+	 If in doubt, say N.
+
 config X86_PCC_CPUFREQ
 	tristate "Processor Clocking Control interface driver"
 	depends on ACPI && ACPI_PROCESSOR
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 1bc90e1..71ad49e 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -38,6 +38,7 @@ obj-$(CONFIG_X86_SPEEDSTEP_SMI)		+= speedstep-smi.o
 obj-$(CONFIG_X86_SPEEDSTEP_CENTRINO)	+= speedstep-centrino.o
 obj-$(CONFIG_X86_P4_CLOCKMOD)		+= p4-clockmod.o
 obj-$(CONFIG_X86_CPUFREQ_NFORCE2)	+= cpufreq-nforce2.o
+obj-$(CONFIG_X86_SNB_CPUFREQ)		+= cpufreq_snb.o
 
 ##################################################################################
 # ARM SoC drivers
diff --git a/drivers/cpufreq/cpufreq_snb.c b/drivers/cpufreq/cpufreq_snb.c
new file mode 100644
index 0000000..0d46862
--- /dev/null
+++ b/drivers/cpufreq/cpufreq_snb.c
@@ -0,0 +1,727 @@
+/*
+ * cpufreq_snb.c: Native P state management for Intel processors
+ *
+ * (C) Copyright 2012 Intel Corporation
+ * Author: Dirk Brandewie <dirk.j.brandewie@...el.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/cpufreq.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+#include <trace/events/power.h>
+
+#include <asm/div64.h>
+#include <asm/msr.h>
+#include <asm/cpu_device_id.h>
+
+#define SAMPLE_COUNT		3
+
+struct sampling_state {
+	int idle_mode;
+	int first_sample;
+};
+
+struct sample {
+	ktime_t start_time;
+	ktime_t end_time;
+	int core_pct_busy;
+	int freq_pct_busy;
+	u64 duration_us;
+	u64 idletime_us;
+	u64 aperf;
+	u64 mperf;
+};
+
+struct freqdata {
+	int	current_freq;
+	int	min_freq;
+	int	max_freq;
+	int	turbo_freq;
+};
+
+struct _pid {
+	int setpoint;
+	int32_t integral;
+	int32_t p_gain;
+	int32_t i_gain;
+	int32_t d_gain;
+	int deadband;
+	int last_err;
+};
+
+struct cpudata {
+	int cpu;
+
+	char name[64];
+
+	struct timer_list timer;
+
+	struct freq_adjust_policy *freq_policy;
+	struct freqdata clock;
+	struct sampling_state sampling_state;
+	struct _pid pid;
+	struct _pid idle_pid;
+
+	int min_freq_count;
+
+	ktime_t prev_sample;
+	u64	prev_idle_time_us;
+	u64	prev_aperf;
+	u64	prev_mperf;
+	int	sample_ptr;
+	struct sample samples[SAMPLE_COUNT];
+};
+
+static unsigned int snb_usage;
+static DEFINE_MUTEX(snb_mutex);
+
+struct cpudata **all_cpu_data;
+struct freq_adjust_policy {
+	int sample_rate_ms;    /* sample rate */
+	int deadband; /*adjust freq on last sample or average */
+	int setpoint; /* starting freq when we have no info */
+	int p_gain_pct;
+	int d_gain_pct;
+	int i_gain_pct;
+};
+
+struct freq_adjust_policy default_policy = {
+	.sample_rate_ms = 10,
+	.deadband = 0,
+	.setpoint = 109,
+	.p_gain_pct = 17,
+	.d_gain_pct = 0,
+	.i_gain_pct = 4,
+};
+
+#define FRAC_BITS 8
+#define int_tofp(X) ((int64_t)(X) << FRAC_BITS)
+#define fp_toint(X) ((X) >> 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);
+}
+
+
+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 inline int pid_calc(struct _pid *pid, int busy)
+{
+	int err, result;
+	int32_t pterm, dterm, fp_error;
+	int32_t integral_limit;
+
+	integral_limit = int_tofp(30);
+	err = pid->setpoint - busy;
+
+	if (abs(err) <= pid->deadband)
+		return 0;
+
+	fp_error = int_tofp(err);
+	pterm = mul_fp(pid->p_gain, fp_error);
+	pid->integral += mul_fp(pid->i_gain, fp_error);
+
+	/* limit the integral term */
+	if (pid->integral > integral_limit)
+		pid->integral = integral_limit;
+	if (pid->integral < -integral_limit)
+		pid->integral = -integral_limit;
+
+	dterm = mul_fp(pid->d_gain, (err - pid->last_err));
+	result = pterm + pid->integral + dterm;
+
+	pid->last_err = err;
+	return fp_toint(result);
+}
+
+
+static inline void snb_busy_pid_reset(struct cpudata *cpu)
+{
+	pid_reset(&cpu->pid,
+		cpu->freq_policy->setpoint,
+		100,
+		cpu->freq_policy->deadband,
+		0);
+
+	pid_p_gain_set(&cpu->pid, cpu->freq_policy->p_gain_pct);
+	pid_d_gain_set(&cpu->pid, cpu->freq_policy->d_gain_pct);
+	pid_i_gain_set(&cpu->pid, cpu->freq_policy->i_gain_pct);
+}
+
+static inline void snb_idle_pid_reset(struct cpudata *cpu)
+{
+	pid_reset(&cpu->idle_pid,
+		75,
+		50,
+		cpu->freq_policy->deadband,
+		0);
+
+	pid_p_gain_set(&cpu->idle_pid, cpu->freq_policy->p_gain_pct);
+	pid_d_gain_set(&cpu->idle_pid, cpu->freq_policy->d_gain_pct);
+	pid_i_gain_set(&cpu->idle_pid, cpu->freq_policy->i_gain_pct);
+}
+
+static inline void snb_reset_all_pid(void)
+{
+	unsigned int cpu;
+	for_each_online_cpu(cpu) {
+		if (all_cpu_data[cpu])
+			snb_busy_pid_reset(all_cpu_data[cpu]);
+	}
+}
+
+/************************** sysfs begin ************************/
+#define show_one(file_name, object)					\
+	static ssize_t show_##file_name					\
+	(struct kobject *kobj, struct attribute *attr, char *buf)	\
+	{								\
+		return sprintf(buf, "%u\n", default_policy.object);	\
+	}
+
+static ssize_t store_sample_rate_ms(struct kobject *a, struct attribute *b,
+				const char *buf, size_t count)
+{
+	unsigned int input;
+	int ret;
+	ret = sscanf(buf, "%u", &input);
+	if (ret != 1)
+		return -EINVAL;
+	default_policy.sample_rate_ms = input;
+	snb_reset_all_pid();
+	return count;
+}
+
+static ssize_t store_d_gain_pct(struct kobject *a, struct attribute *b,
+				const char *buf, size_t count)
+{
+	unsigned int input;
+	int ret;
+	ret = sscanf(buf, "%u", &input);
+	if (ret != 1)
+		return -EINVAL;
+	default_policy.d_gain_pct = input;
+	snb_reset_all_pid();
+
+	return count;
+}
+
+static ssize_t store_i_gain_pct(struct kobject *a, struct attribute *b,
+				const char *buf, size_t count)
+{
+	unsigned int input;
+	int ret;
+	ret = sscanf(buf, "%u", &input);
+	if (ret != 1)
+		return -EINVAL;
+	default_policy.i_gain_pct = input;
+	snb_reset_all_pid();
+
+	return count;
+}
+
+static ssize_t store_deadband(struct kobject *a, struct attribute *b,
+			const char *buf, size_t count)
+{
+	unsigned int input;
+	int ret;
+	ret = sscanf(buf, "%u", &input);
+	if (ret != 1)
+		return -EINVAL;
+	default_policy.deadband = input;
+	snb_reset_all_pid();
+
+	return count;
+}
+
+static ssize_t store_setpoint(struct kobject *a, struct attribute *b,
+			const char *buf, size_t count)
+{
+	unsigned int input;
+	int ret;
+	ret = sscanf(buf, "%u", &input);
+	if (ret != 1)
+		return -EINVAL;
+	default_policy.setpoint = input;
+	snb_reset_all_pid();
+
+	return count;
+}
+
+static ssize_t store_p_gain_pct(struct kobject *a, struct attribute *b,
+				const char *buf, size_t count)
+{
+	unsigned int input;
+	int ret;
+	ret = sscanf(buf, "%u", &input);
+	if (ret != 1)
+		return -EINVAL;
+	default_policy.p_gain_pct = input;
+	snb_reset_all_pid();
+
+	return count;
+}
+
+show_one(sample_rate_ms, sample_rate_ms);
+show_one(d_gain_pct, d_gain_pct);
+show_one(i_gain_pct, i_gain_pct);
+show_one(deadband, deadband);
+show_one(setpoint, setpoint);
+show_one(p_gain_pct, p_gain_pct);
+
+
+define_one_global_rw(sample_rate_ms);
+define_one_global_rw(d_gain_pct);
+define_one_global_rw(i_gain_pct);
+define_one_global_rw(deadband);
+define_one_global_rw(setpoint);
+define_one_global_rw(p_gain_pct);
+
+
+static struct attribute *snb_attributes[] = {
+	&sample_rate_ms.attr,
+	&d_gain_pct.attr,
+	&i_gain_pct.attr,
+	&deadband.attr,
+	&setpoint.attr,
+	&p_gain_pct.attr,
+	NULL
+};
+
+static struct attribute_group snb_attr_group = {
+	.attrs = snb_attributes,
+	.name = "snb",
+};
+
+/************************** sysfs end ************************/
+
+static int snb_get_min_freq(void)
+{
+	u64 value;
+	rdmsrl(0xCE, value);
+	return (value >> 40) & 0xFF;
+}
+
+static int snb_get_max_freq(void)
+{
+	u64 value;
+	rdmsrl(0xCE, value);
+	return (value >> 8) & 0xFF;
+}
+
+static int snb_get_turbo_freq(void)
+{
+	u64 value;
+	int nont, ret;
+	rdmsrl(0x1AD, value);
+	nont = snb_get_max_freq();
+	ret = ((value) & 255);
+	if (ret <= nont)
+		ret = nont;
+	return ret;
+}
+
+
+static void snb_set_freq(struct cpudata *cpu, int clock)
+{
+	clock = clamp_t(int, clock, cpu->clock.min_freq, cpu->clock.turbo_freq);
+
+	if (clock == cpu->clock.current_freq)
+		return;
+
+#ifndef MODULE
+	trace_cpu_frequency(clock * 100000, cpu->cpu);
+	trace_power_frequency(POWER_PSTATE, clock * 100000, cpu->cpu);
+#endif
+
+	cpu->clock.current_freq = clock;
+	wrmsrl(MSR_IA32_PERF_CTL, clock << 8);
+}
+
+static inline void snb_freq_increase(struct cpudata *cpu, int steps)
+{
+	int target;
+	target = cpu->clock.current_freq + steps;
+
+	snb_set_freq(cpu, target);
+}
+
+static inline void snb_freq_decrease(struct cpudata *cpu, int steps)
+{
+	int target;
+	target = cpu->clock.current_freq - steps;
+	snb_set_freq(cpu, target);
+}
+
+static void snb_get_cpu_freqs(struct cpudata *cpu)
+{
+	sprintf(cpu->name, "Intel 2nd generation core");
+
+	cpu->clock.min_freq = snb_get_min_freq();
+	cpu->clock.max_freq = snb_get_max_freq();
+	cpu->clock.turbo_freq = snb_get_turbo_freq();
+
+	/* goto max clock so we don't slow up boot if we are built-in
+	   if we are a module we will take care of it during normal
+	   operation
+	*/
+	snb_set_freq(cpu, cpu->clock.max_freq);
+}
+
+
+static inline void snb_calc_busy(struct cpudata *cpu, struct sample *sample)
+{
+	u64 core_pct;
+
+	sample->freq_pct_busy = 100 - div64_u64(
+					sample->idletime_us * 100,
+					sample->duration_us);
+	core_pct = div64_u64(sample->aperf * 100, sample->mperf);
+	sample->core_pct_busy = sample->freq_pct_busy * core_pct / 100;
+}
+
+static inline int snb_sample(struct cpudata *cpu)
+{
+	ktime_t now;
+	u64 idle_time_us;
+	u64 aperf, mperf;
+
+	now = ktime_get();
+	idle_time_us = get_cpu_idle_time_us(cpu->cpu, NULL);
+
+	rdmsrl(MSR_IA32_APERF, aperf);
+	rdmsrl(MSR_IA32_MPERF, mperf);
+	/* for the first sample, don't actually record a sample, just
+	 * set the baseline */
+	if (cpu->prev_idle_time_us > 0) {
+		cpu->sample_ptr = (cpu->sample_ptr + 1) % SAMPLE_COUNT;
+		cpu->samples[cpu->sample_ptr].start_time = cpu->prev_sample;
+		cpu->samples[cpu->sample_ptr].end_time = now;
+		cpu->samples[cpu->sample_ptr].duration_us =
+			ktime_us_delta(now, cpu->prev_sample);
+		cpu->samples[cpu->sample_ptr].idletime_us =
+			idle_time_us - cpu->prev_idle_time_us;
+
+		cpu->samples[cpu->sample_ptr].aperf = aperf;
+		cpu->samples[cpu->sample_ptr].mperf = mperf;
+		cpu->samples[cpu->sample_ptr].aperf -= cpu->prev_aperf;
+		cpu->samples[cpu->sample_ptr].mperf -= cpu->prev_mperf;
+
+		snb_calc_busy(cpu, &cpu->samples[cpu->sample_ptr]);
+	}
+
+	cpu->prev_sample = now;
+	cpu->prev_idle_time_us = idle_time_us;
+	cpu->prev_aperf = aperf;
+	cpu->prev_mperf = mperf;
+	return cpu->sample_ptr;
+}
+
+static inline void snb_set_sample_time(struct cpudata *cpu)
+{
+	int sample_time;
+	int delay;
+
+	sample_time = cpu->freq_policy->sample_rate_ms;
+	delay = msecs_to_jiffies(sample_time);
+	delay -= jiffies % delay;
+	mod_timer(&cpu->timer, jiffies + delay);
+}
+
+static inline void snb_idle_mode(struct cpudata *cpu)
+{
+	cpu->sampling_state.idle_mode = 1;
+}
+
+static inline void snb_normal_mode(struct cpudata *cpu)
+{
+	cpu->sampling_state.idle_mode = 0;
+}
+
+static inline int snb_get_scaled_busy(struct cpudata *cpu)
+{
+	int32_t busy_scaled;
+	int32_t core_busy, turbo_freq, current_freq;
+
+	core_busy    = int_tofp(cpu->samples[cpu->sample_ptr].core_pct_busy);
+	turbo_freq   = int_tofp(cpu->clock.turbo_freq);
+	current_freq = int_tofp(cpu->clock.current_freq);
+	busy_scaled = mul_fp(core_busy, div_fp(turbo_freq, current_freq));
+
+	return fp_toint(busy_scaled);
+}
+
+static inline void snb_adjust_busy_freq(struct cpudata *cpu)
+{
+	int busy_scaled;
+	struct _pid *pid;
+	int ctl = 0;
+	int steps;
+
+	pid = &cpu->pid;
+
+	busy_scaled =  snb_get_scaled_busy(cpu);
+
+	ctl = pid_calc(pid, busy_scaled);
+
+	steps = abs(ctl);
+	if (ctl < 0)
+		snb_freq_increase(cpu, steps);
+	else
+		snb_freq_decrease(cpu, steps);
+}
+
+static inline void snb_adjust_idle_freq(struct cpudata *cpu)
+{
+	int busy_scaled;
+	struct _pid *pid;
+	int ctl = 0;
+	int steps;
+
+	pid = &cpu->idle_pid;
+
+	busy_scaled =  snb_get_scaled_busy(cpu);
+
+	ctl = pid_calc(pid, 100 - busy_scaled);
+
+	steps = abs(ctl);
+	if (ctl < 0)
+		snb_freq_decrease(cpu, steps);
+	else
+		snb_freq_increase(cpu, steps);
+
+	if (cpu->clock.current_freq == cpu->clock.min_freq)
+		snb_normal_mode(cpu);
+}
+static inline int snb_valid_sample(struct cpudata *cpu, int idx)
+{
+	struct sample *sample = &cpu->samples[idx];
+
+	return sample->duration_us <
+		(cpu->freq_policy->sample_rate_ms * USEC_PER_MSEC  * 2);
+}
+
+static void snb_timer_func(unsigned long __data)
+{
+	struct cpudata *cpu = (struct cpudata *) __data;
+	struct freq_adjust_policy *policy;
+	int idx;
+
+	policy = cpu->freq_policy;
+
+	idx = snb_sample(cpu);
+
+	if (snb_valid_sample(cpu, idx)) {
+		if (!cpu->sampling_state.idle_mode)
+			snb_adjust_busy_freq(cpu);
+		else
+			snb_adjust_idle_freq(cpu);
+	}
+
+#if defined(XPERF_FIX)
+	if (cpu->clock.current_freq == cpu->clock.min_freq) {
+		cpu->min_freq_count++;
+		if (!(cpu->min_freq_count % 5)) {
+			snb_set_freq(cpu, cpu->clock.max_freq);
+			snb_idle_mode(cpu);
+		}
+	} else
+		cpu->min_freq_count = 0;
+#endif
+	snb_set_sample_time(cpu);
+}
+
+static void snb_exit(unsigned int cpu)
+{
+	if (!all_cpu_data)
+		return;
+	pr_info("snb: disabling %d\n", cpu);
+	if (all_cpu_data[cpu]) {
+		del_timer_sync(&all_cpu_data[cpu]->timer);
+		kfree(all_cpu_data[cpu]);
+	}
+}
+
+#define ICPU(model, policy) \
+	{ X86_VENDOR_INTEL, 6, model, X86_FEATURE_ANY, (unsigned long)&policy }
+
+static const struct x86_cpu_id intel_cpufreq_ids[] = {
+	ICPU(0x2a, default_policy),
+	ICPU(0x2d, default_policy),
+	{}
+};
+MODULE_DEVICE_TABLE(x86cpu, intel_cpufreq_ids);
+
+static int snb_init(unsigned int cpu)
+{
+	int rc;
+	const struct x86_cpu_id *id;
+
+	id = x86_match_cpu(intel_cpufreq_ids);
+	if (!id)
+		return -ENODEV;
+
+	all_cpu_data[cpu] = kzalloc(sizeof(struct cpudata), GFP_KERNEL);
+	if (!all_cpu_data[cpu]) {
+		rc = -ENOMEM;
+		goto unwind;
+	}
+
+	snb_get_cpu_freqs(all_cpu_data[cpu]);
+
+	all_cpu_data[cpu]->cpu = cpu;
+	all_cpu_data[cpu]->freq_policy =
+		(struct freq_adjust_policy *)id->driver_data;
+	init_timer_deferrable(&all_cpu_data[cpu]->timer);
+	all_cpu_data[cpu]->timer.function = snb_timer_func;
+	all_cpu_data[cpu]->timer.data =
+		(unsigned long)all_cpu_data[cpu];
+	all_cpu_data[cpu]->timer.expires = jiffies + HZ/100;
+	snb_busy_pid_reset(all_cpu_data[cpu]);
+	snb_idle_pid_reset(all_cpu_data[cpu]);
+	pr_info("snb: enabling %d\n", cpu);
+	add_timer_on(&all_cpu_data[cpu]->timer, cpu);
+	return 0;
+
+unwind:
+	snb_exit(cpu);
+	return -ENODEV;
+}
+
+/**
+ * cpufreq_set - set the CPU frequency
+ * @policy: pointer to policy struct where freq is being set
+ * @freq: target frequency in kHz
+ *
+ * Sets the CPU frequency to freq.
+ */
+static int cpufreq_snb_set(struct cpufreq_policy *policy, unsigned int freq)
+{
+	int ret = 0;
+	return ret;
+}
+
+
+static ssize_t cpufreq_snb_show_speed(struct cpufreq_policy *policy, char *buf)
+{
+	return 0;
+}
+
+static int cpufreq_snb(struct cpufreq_policy *policy,
+				   unsigned int event)
+{
+	unsigned int cpu = policy->cpu;
+	int rc = 0;
+
+	switch (event) {
+	case CPUFREQ_GOV_START:
+		if (!cpu_online(cpu))
+			return -EINVAL;
+		mutex_lock(&snb_mutex);
+		snb_usage++;
+		rc = snb_init(cpu);
+
+		if (snb_usage == 1)
+			rc = sysfs_create_group(cpufreq_global_kobject,
+						&snb_attr_group);
+
+		mutex_unlock(&snb_mutex);
+		break;
+	case CPUFREQ_GOV_STOP:
+		mutex_lock(&snb_mutex);
+		snb_usage--;
+		snb_exit(cpu);
+		if (!snb_usage)
+			sysfs_remove_group(cpufreq_global_kobject,
+					&snb_attr_group);
+
+		mutex_unlock(&snb_mutex);
+		break;
+	case CPUFREQ_GOV_LIMITS:
+		mutex_lock(&snb_mutex);
+		mutex_unlock(&snb_mutex);
+		break;
+	}
+	return rc;
+}
+
+static struct cpufreq_governor cpufreq_gov_snb = {
+	.name		= "snb",
+	.governor	= cpufreq_snb,
+	.store_setspeed	= cpufreq_snb_set,
+	.show_setspeed	= cpufreq_snb_show_speed,
+	.owner		= THIS_MODULE,
+};
+
+static int __init cpufreq_gov_snb_init(void)
+{
+	pr_info("Sandybridge frequency driver initializing.\n");
+
+	all_cpu_data = vmalloc(sizeof(void *) * num_possible_cpus());
+	if (!all_cpu_data)
+		return -ENOMEM;
+	memset(all_cpu_data, 0, sizeof(void *) * num_possible_cpus());
+
+
+	return cpufreq_register_governor(&cpufreq_gov_snb);
+}
+
+static void __exit cpufreq_gov_snb_exit(void)
+{
+	vfree(all_cpu_data);
+	all_cpu_data = NULL;
+	cpufreq_unregister_governor(&cpufreq_gov_snb);
+}
+
+
+MODULE_AUTHOR("Dirk Brandewie <dirk.j.brandewie@...el.com>");
+MODULE_DESCRIPTION("'cpufreq_snb' - cpufreq governor for Sandy Bridge");
+MODULE_LICENSE("GPL");
+
+
+fs_initcall(cpufreq_gov_snb_init);
+module_exit(cpufreq_gov_snb_exit);
-- 
1.7.7.6

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