drivers/cpufreq/e_powersaver.c - linux-imx - Git at Google

 /*
  *  Based on documentation provided by Dave Jones. Thanks!
  *
  *  Licensed under the terms of the GNU GPL License version 2.
  *
  *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/cpufreq.h>
 #include <linux/ioport.h>
 #include <linux/slab.h>
 #include <linux/timex.h>
 #include <linux/io.h>
 #include <linux/delay.h>

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

 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
 #include <linux/acpi.h>
 #include <acpi/processor.h>
 #endif

 #define EPS_BRAND_C7M	0
 #define EPS_BRAND_C7	1
 #define EPS_BRAND_EDEN	2
 #define EPS_BRAND_C3	3
 #define EPS_BRAND_C7D	4

 struct eps_cpu_data {
 	u32 fsb;
 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
 	u32 bios_limit;
 #endif
 	struct cpufreq_frequency_table freq_table[];
 };

 static struct eps_cpu_data *eps_cpu[NR_CPUS];

 /* Module parameters */
 static int freq_failsafe_off;
 static int voltage_failsafe_off;
 static int set_max_voltage;

 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
 static int ignore_acpi_limit;

 static struct acpi_processor_performance *eps_acpi_cpu_perf;

 /* Minimum necessary to get acpi_processor_get_bios_limit() working */
 static int eps_acpi_init(void)
 {
 	eps_acpi_cpu_perf = kzalloc(sizeof(*eps_acpi_cpu_perf),
 				      GFP_KERNEL);
 	if (!eps_acpi_cpu_perf)
 		return -ENOMEM;

 	if (!zalloc_cpumask_var(&eps_acpi_cpu_perf->shared_cpu_map,
 								GFP_KERNEL)) {
 		kfree(eps_acpi_cpu_perf);
 		eps_acpi_cpu_perf = NULL;
 		return -ENOMEM;
 	}

 	if (acpi_processor_register_performance(eps_acpi_cpu_perf, 0)) {
 		free_cpumask_var(eps_acpi_cpu_perf->shared_cpu_map);
 		kfree(eps_acpi_cpu_perf);
 		eps_acpi_cpu_perf = NULL;
 		return -EIO;
 	}
 	return 0;
 }

 static int eps_acpi_exit(struct cpufreq_policy *policy)
 {
 	if (eps_acpi_cpu_perf) {
 		acpi_processor_unregister_performance(0);
 		free_cpumask_var(eps_acpi_cpu_perf->shared_cpu_map);
 		kfree(eps_acpi_cpu_perf);
 		eps_acpi_cpu_perf = NULL;
 	}
 	return 0;
 }
 #endif

 static unsigned int eps_get(unsigned int cpu)
 {
 	struct eps_cpu_data *centaur;
 	u32 lo, hi;

 	if (cpu)
 		return 0;
 	centaur = eps_cpu[cpu];
 	if (centaur == NULL)
 		return 0;

 	/* Return current frequency */
 	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
 	return centaur->fsb * ((lo >> 8) & 0xff);
 }

 static int eps_set_state(struct eps_cpu_data *centaur,
 			 struct cpufreq_policy *policy,
 			 u32 dest_state)
 {
 	u32 lo, hi;
 	int i;

 	/* Wait while CPU is busy */
 	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
 	i = 0;
 	while (lo & ((1 << 16) | (1 << 17))) {
 		udelay(16);
 		rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
 		i++;
 		if (unlikely(i > 64)) {
 			return -ENODEV;
 		}
 	}
 	/* Set new multiplier and voltage */
 	wrmsr(MSR_IA32_PERF_CTL, dest_state & 0xffff, 0);
 	/* Wait until transition end */
 	i = 0;
 	do {
 		udelay(16);
 		rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
 		i++;
 		if (unlikely(i > 64)) {
 			return -ENODEV;
 		}
 	} while (lo & ((1 << 16) | (1 << 17)));

 #ifdef DEBUG
 	{
 	u8 current_multiplier, current_voltage;

 	/* Print voltage and multiplier */
 	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
 	current_voltage = lo & 0xff;
 	pr_info("Current voltage = %dmV\n", current_voltage * 16 + 700);
 	current_multiplier = (lo >> 8) & 0xff;
 	pr_info("Current multiplier = %d\n", current_multiplier);
 	}
 #endif
 	return 0;
 }

 static int eps_target(struct cpufreq_policy *policy, unsigned int index)
 {
 	struct eps_cpu_data *centaur;
 	unsigned int cpu = policy->cpu;
 	unsigned int dest_state;
 	int ret;

 	if (unlikely(eps_cpu[cpu] == NULL))
 		return -ENODEV;
 	centaur = eps_cpu[cpu];

 	/* Make frequency transition */
 	dest_state = centaur->freq_table[index].driver_data & 0xffff;
 	ret = eps_set_state(centaur, policy, dest_state);
 	if (ret)
 		pr_err("Timeout!\n");
 	return ret;
 }

 static int eps_cpu_init(struct cpufreq_policy *policy)
 {
 	unsigned int i;
 	u32 lo, hi;
 	u64 val;
 	u8 current_multiplier, current_voltage;
 	u8 max_multiplier, max_voltage;
 	u8 min_multiplier, min_voltage;
 	u8 brand = 0;
 	u32 fsb;
 	struct eps_cpu_data *centaur;
 	struct cpuinfo_x86 *c = &cpu_data(0);
 	struct cpufreq_frequency_table *f_table;
 	int k, step, voltage;
 	int ret;
 	int states;
 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
 	unsigned int limit;
 #endif

 	if (policy->cpu != 0)
 		return -ENODEV;

 	/* Check brand */
 	pr_info("Detected VIA ");

 	switch (c->x86_model) {
 	case 10:
 		rdmsr(0x1153, lo, hi);
 		brand = (((lo >> 2) ^ lo) >> 18) & 3;
 		pr_cont("Model A ");
 		break;
 	case 13:
 		rdmsr(0x1154, lo, hi);
 		brand = (((lo >> 4) ^ (lo >> 2))) & 0x000000ff;
 		pr_cont("Model D ");
 		break;
 	}

 	switch (brand) {
 	case EPS_BRAND_C7M:
 		pr_cont("C7-M\n");
 		break;
 	case EPS_BRAND_C7:
 		pr_cont("C7\n");
 		break;
 	case EPS_BRAND_EDEN:
 		pr_cont("Eden\n");
 		break;
 	case EPS_BRAND_C7D:
 		pr_cont("C7-D\n");
 		break;
 	case EPS_BRAND_C3:
 		pr_cont("C3\n");
 		return -ENODEV;
 		break;
 	}
 	/* Enable Enhanced PowerSaver */
 	rdmsrl(MSR_IA32_MISC_ENABLE, val);
 	if (!(val & MSR_IA32_MISC_ENABLE_ENHANCED_SPEEDSTEP)) {
 		val |= MSR_IA32_MISC_ENABLE_ENHANCED_SPEEDSTEP;
 		wrmsrl(MSR_IA32_MISC_ENABLE, val);
 		/* Can be locked at 0 */
 		rdmsrl(MSR_IA32_MISC_ENABLE, val);
 		if (!(val & MSR_IA32_MISC_ENABLE_ENHANCED_SPEEDSTEP)) {
 			pr_info("Can't enable Enhanced PowerSaver\n");
 			return -ENODEV;
 		}
 	}

 	/* Print voltage and multiplier */
 	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
 	current_voltage = lo & 0xff;
 	pr_info("Current voltage = %dmV\n", current_voltage * 16 + 700);
 	current_multiplier = (lo >> 8) & 0xff;
 	pr_info("Current multiplier = %d\n", current_multiplier);

 	/* Print limits */
 	max_voltage = hi & 0xff;
 	pr_info("Highest voltage = %dmV\n", max_voltage * 16 + 700);
 	max_multiplier = (hi >> 8) & 0xff;
 	pr_info("Highest multiplier = %d\n", max_multiplier);
 	min_voltage = (hi >> 16) & 0xff;
 	pr_info("Lowest voltage = %dmV\n", min_voltage * 16 + 700);
 	min_multiplier = (hi >> 24) & 0xff;
 	pr_info("Lowest multiplier = %d\n", min_multiplier);

 	/* Sanity checks */
 	if (current_multiplier == 0 || max_multiplier == 0
 	    || min_multiplier == 0)
 		return -EINVAL;
 	if (current_multiplier > max_multiplier
 	    || max_multiplier <= min_multiplier)
 		return -EINVAL;
 	if (current_voltage > 0x1f || max_voltage > 0x1f)
 		return -EINVAL;
 	if (max_voltage < min_voltage
 	    || current_voltage < min_voltage
 	    || current_voltage > max_voltage)
 		return -EINVAL;

 	/* Check for systems using underclocked CPU */
 	if (!freq_failsafe_off && max_multiplier != current_multiplier) {
 		pr_info("Your processor is running at different frequency then its maximum. Aborting.\n");
 		pr_info("You can use freq_failsafe_off option to disable this check.\n");
 		return -EINVAL;
 	}
 	if (!voltage_failsafe_off && max_voltage != current_voltage) {
 		pr_info("Your processor is running at different voltage then its maximum. Aborting.\n");
 		pr_info("You can use voltage_failsafe_off option to disable this check.\n");
 		return -EINVAL;
 	}

 	/* Calc FSB speed */
 	fsb = cpu_khz / current_multiplier;

 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
 	/* Check for ACPI processor speed limit */
 	if (!ignore_acpi_limit && !eps_acpi_init()) {
 		if (!acpi_processor_get_bios_limit(policy->cpu, &limit)) {
 			pr_info("ACPI limit %u.%uGHz\n",
 				limit/1000000,
 				(limit%1000000)/10000);
 			eps_acpi_exit(policy);
 			/* Check if max_multiplier is in BIOS limits */
 			if (limit && max_multiplier * fsb > limit) {
 				pr_info("Aborting\n");
 				return -EINVAL;
 			}
 		}
 	}
 #endif

 	/* Allow user to set lower maximum voltage then that reported
 	 * by processor */
 	if (brand == EPS_BRAND_C7M && set_max_voltage) {
 		u32 v;

 		/* Change mV to something hardware can use */
 		v = (set_max_voltage - 700) / 16;
 		/* Check if voltage is within limits */
 		if (v >= min_voltage && v <= max_voltage) {
 			pr_info("Setting %dmV as maximum\n", v * 16 + 700);
 			max_voltage = v;
 		}
 	}

 	/* Calc number of p-states supported */
 	if (brand == EPS_BRAND_C7M)
 		states = max_multiplier - min_multiplier + 1;
 	else
 		states = 2;

 	/* Allocate private data and frequency table for current cpu */
 	centaur = kzalloc(sizeof(*centaur)
 		    + (states + 1) * sizeof(struct cpufreq_frequency_table),
 		    GFP_KERNEL);
 	if (!centaur)
 		return -ENOMEM;
 	eps_cpu[0] = centaur;

 	/* Copy basic values */
 	centaur->fsb = fsb;
 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
 	centaur->bios_limit = limit;
 #endif

 	/* Fill frequency and MSR value table */
 	f_table = &centaur->freq_table[0];
 	if (brand != EPS_BRAND_C7M) {
 		f_table[0].frequency = fsb * min_multiplier;
 		f_table[0].driver_data = (min_multiplier << 8) | min_voltage;
 		f_table[1].frequency = fsb * max_multiplier;
 		f_table[1].driver_data = (max_multiplier << 8) | max_voltage;
 		f_table[2].frequency = CPUFREQ_TABLE_END;
 	} else {
 		k = 0;
 		step = ((max_voltage - min_voltage) * 256)
 			/ (max_multiplier - min_multiplier);
 		for (i = min_multiplier; i <= max_multiplier; i++) {
 			voltage = (k * step) / 256 + min_voltage;
 			f_table[k].frequency = fsb * i;
 			f_table[k].driver_data = (i << 8) | voltage;
 			k++;
 		}
 		f_table[k].frequency = CPUFREQ_TABLE_END;
 	}

 	policy->cpuinfo.transition_latency = 140000; /* 844mV -> 700mV in ns */

 	ret = cpufreq_table_validate_and_show(policy, &centaur->freq_table[0]);
 	if (ret) {
 		kfree(centaur);
 		return ret;
 	}

 	return 0;
 }

 static int eps_cpu_exit(struct cpufreq_policy *policy)
 {
 	unsigned int cpu = policy->cpu;

 	/* Bye */
 	kfree(eps_cpu[cpu]);
 	eps_cpu[cpu] = NULL;
 	return 0;
 }

 static struct cpufreq_driver eps_driver = {
 	.verify		= cpufreq_generic_frequency_table_verify,
 	.target_index	= eps_target,
 	.init		= eps_cpu_init,
 	.exit		= eps_cpu_exit,
 	.get		= eps_get,
 	.name		= "e_powersaver",
 	.attr		= cpufreq_generic_attr,
 };


 /* This driver will work only on Centaur C7 processors with
  * Enhanced SpeedStep/PowerSaver registers */
 static const struct x86_cpu_id eps_cpu_id[] = {
 	{ X86_VENDOR_CENTAUR, 6, X86_MODEL_ANY, X86_FEATURE_EST },
 	{}
 };
 MODULE_DEVICE_TABLE(x86cpu, eps_cpu_id);

 static int __init eps_init(void)
 {
 	if (!x86_match_cpu(eps_cpu_id) || boot_cpu_data.x86_model < 10)
 		return -ENODEV;
 	if (cpufreq_register_driver(&eps_driver))
 		return -EINVAL;
 	return 0;
 }

 static void __exit eps_exit(void)
 {
 	cpufreq_unregister_driver(&eps_driver);
 }

 /* Allow user to overclock his machine or to change frequency to higher after
  * unloading module */
 module_param(freq_failsafe_off, int, 0644);
 MODULE_PARM_DESC(freq_failsafe_off, "Disable current vs max frequency check");
 module_param(voltage_failsafe_off, int, 0644);
 MODULE_PARM_DESC(voltage_failsafe_off, "Disable current vs max voltage check");
 #if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
 module_param(ignore_acpi_limit, int, 0644);
 MODULE_PARM_DESC(ignore_acpi_limit, "Don't check ACPI's processor speed limit");
 #endif
 module_param(set_max_voltage, int, 0644);
 MODULE_PARM_DESC(set_max_voltage, "Set maximum CPU voltage (mV) C7-M only");

 MODULE_AUTHOR("Rafal Bilski <rafalbilski@interia.pl>");
 MODULE_DESCRIPTION("Enhanced PowerSaver driver for VIA C7 CPU's.");
 MODULE_LICENSE("GPL");

 module_init(eps_init);
 module_exit(eps_exit);
	/*
	* Based on documentation provided by Dave Jones. Thanks!
	*
	* Licensed under the terms of the GNU GPL License version 2.
	*
	* BIG FAT DISCLAIMER: Work in progress code. Possibly dangerous
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/cpufreq.h>
	#include <linux/ioport.h>
	#include <linux/slab.h>
	#include <linux/timex.h>
	#include <linux/io.h>
	#include <linux/delay.h>

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

	#if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
	#include <linux/acpi.h>
	#include <acpi/processor.h>
	#endif

	#define EPS_BRAND_C7M 0
	#define EPS_BRAND_C7 1
	#define EPS_BRAND_EDEN 2
	#define EPS_BRAND_C3 3
	#define EPS_BRAND_C7D 4

	struct eps_cpu_data {
	u32 fsb;
	#if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
	u32 bios_limit;
	#endif
	struct cpufreq_frequency_table freq_table[];
	};

	static struct eps_cpu_data *eps_cpu[NR_CPUS];

	/* Module parameters */
	static int freq_failsafe_off;
	static int voltage_failsafe_off;
	static int set_max_voltage;

	#if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
	static int ignore_acpi_limit;

	static struct acpi_processor_performance *eps_acpi_cpu_perf;

	/* Minimum necessary to get acpi_processor_get_bios_limit() working */
	static int eps_acpi_init(void)
	{
	eps_acpi_cpu_perf = kzalloc(sizeof(*eps_acpi_cpu_perf),
	GFP_KERNEL);
	if (!eps_acpi_cpu_perf)
	return -ENOMEM;

	if (!zalloc_cpumask_var(&eps_acpi_cpu_perf->shared_cpu_map,
	GFP_KERNEL)) {
	kfree(eps_acpi_cpu_perf);
	eps_acpi_cpu_perf = NULL;
	return -ENOMEM;
	}

	if (acpi_processor_register_performance(eps_acpi_cpu_perf, 0)) {
	free_cpumask_var(eps_acpi_cpu_perf->shared_cpu_map);
	kfree(eps_acpi_cpu_perf);
	eps_acpi_cpu_perf = NULL;
	return -EIO;
	}
	return 0;
	}

	static int eps_acpi_exit(struct cpufreq_policy *policy)
	{
	if (eps_acpi_cpu_perf) {
	acpi_processor_unregister_performance(0);
	free_cpumask_var(eps_acpi_cpu_perf->shared_cpu_map);
	kfree(eps_acpi_cpu_perf);
	eps_acpi_cpu_perf = NULL;
	}
	return 0;
	}
	#endif

	static unsigned int eps_get(unsigned int cpu)
	{
	struct eps_cpu_data *centaur;
	u32 lo, hi;

	if (cpu)
	return 0;
	centaur = eps_cpu[cpu];
	if (centaur == NULL)
	return 0;

	/* Return current frequency */
	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
	return centaur->fsb * ((lo >> 8) & 0xff);
	}

	static int eps_set_state(struct eps_cpu_data *centaur,
	struct cpufreq_policy *policy,
	u32 dest_state)
	{
	u32 lo, hi;
	int i;

	/* Wait while CPU is busy */
	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
	i = 0;
	while (lo & ((1 << 16) \| (1 << 17))) {
	udelay(16);
	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
	i++;
	if (unlikely(i > 64)) {
	return -ENODEV;
	}
	}
	/* Set new multiplier and voltage */
	wrmsr(MSR_IA32_PERF_CTL, dest_state & 0xffff, 0);
	/* Wait until transition end */
	i = 0;
	do {
	udelay(16);
	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
	i++;
	if (unlikely(i > 64)) {
	return -ENODEV;
	}
	} while (lo & ((1 << 16) \| (1 << 17)));

	#ifdef DEBUG
	{
	u8 current_multiplier, current_voltage;

	/* Print voltage and multiplier */
	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
	current_voltage = lo & 0xff;
	pr_info("Current voltage = %dmV\n", current_voltage * 16 + 700);
	current_multiplier = (lo >> 8) & 0xff;
	pr_info("Current multiplier = %d\n", current_multiplier);
	}
	#endif
	return 0;
	}

	static int eps_target(struct cpufreq_policy *policy, unsigned int index)
	{
	struct eps_cpu_data *centaur;
	unsigned int cpu = policy->cpu;
	unsigned int dest_state;
	int ret;

	if (unlikely(eps_cpu[cpu] == NULL))
	return -ENODEV;
	centaur = eps_cpu[cpu];

	/* Make frequency transition */
	dest_state = centaur->freq_table[index].driver_data & 0xffff;
	ret = eps_set_state(centaur, policy, dest_state);
	if (ret)
	pr_err("Timeout!\n");
	return ret;
	}

	static int eps_cpu_init(struct cpufreq_policy *policy)
	{
	unsigned int i;
	u32 lo, hi;
	u64 val;
	u8 current_multiplier, current_voltage;
	u8 max_multiplier, max_voltage;
	u8 min_multiplier, min_voltage;
	u8 brand = 0;
	u32 fsb;
	struct eps_cpu_data *centaur;
	struct cpuinfo_x86 *c = &cpu_data(0);
	struct cpufreq_frequency_table *f_table;
	int k, step, voltage;
	int ret;
	int states;
	#if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
	unsigned int limit;
	#endif

	if (policy->cpu != 0)
	return -ENODEV;

	/* Check brand */
	pr_info("Detected VIA ");

	switch (c->x86_model) {
	case 10:
	rdmsr(0x1153, lo, hi);
	brand = (((lo >> 2) ^ lo) >> 18) & 3;
	pr_cont("Model A ");
	break;
	case 13:
	rdmsr(0x1154, lo, hi);
	brand = (((lo >> 4) ^ (lo >> 2))) & 0x000000ff;
	pr_cont("Model D ");
	break;
	}

	switch (brand) {
	case EPS_BRAND_C7M:
	pr_cont("C7-M\n");
	break;
	case EPS_BRAND_C7:
	pr_cont("C7\n");
	break;
	case EPS_BRAND_EDEN:
	pr_cont("Eden\n");
	break;
	case EPS_BRAND_C7D:
	pr_cont("C7-D\n");
	break;
	case EPS_BRAND_C3:
	pr_cont("C3\n");
	return -ENODEV;
	break;
	}
	/* Enable Enhanced PowerSaver */
	rdmsrl(MSR_IA32_MISC_ENABLE, val);
	if (!(val & MSR_IA32_MISC_ENABLE_ENHANCED_SPEEDSTEP)) {
	val \|= MSR_IA32_MISC_ENABLE_ENHANCED_SPEEDSTEP;
	wrmsrl(MSR_IA32_MISC_ENABLE, val);
	/* Can be locked at 0 */
	rdmsrl(MSR_IA32_MISC_ENABLE, val);
	if (!(val & MSR_IA32_MISC_ENABLE_ENHANCED_SPEEDSTEP)) {
	pr_info("Can't enable Enhanced PowerSaver\n");
	return -ENODEV;
	}
	}

	/* Print voltage and multiplier */
	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
	current_voltage = lo & 0xff;
	pr_info("Current voltage = %dmV\n", current_voltage * 16 + 700);
	current_multiplier = (lo >> 8) & 0xff;
	pr_info("Current multiplier = %d\n", current_multiplier);

	/* Print limits */
	max_voltage = hi & 0xff;
	pr_info("Highest voltage = %dmV\n", max_voltage * 16 + 700);
	max_multiplier = (hi >> 8) & 0xff;
	pr_info("Highest multiplier = %d\n", max_multiplier);
	min_voltage = (hi >> 16) & 0xff;
	pr_info("Lowest voltage = %dmV\n", min_voltage * 16 + 700);
	min_multiplier = (hi >> 24) & 0xff;
	pr_info("Lowest multiplier = %d\n", min_multiplier);

	/* Sanity checks */
	if (current_multiplier == 0 \|\| max_multiplier == 0
	\|\| min_multiplier == 0)
	return -EINVAL;
	if (current_multiplier > max_multiplier
	\|\| max_multiplier <= min_multiplier)
	return -EINVAL;
	if (current_voltage > 0x1f \|\| max_voltage > 0x1f)
	return -EINVAL;
	if (max_voltage < min_voltage
	\|\| current_voltage < min_voltage
	\|\| current_voltage > max_voltage)
	return -EINVAL;

	/* Check for systems using underclocked CPU */
	if (!freq_failsafe_off && max_multiplier != current_multiplier) {
	pr_info("Your processor is running at different frequency then its maximum. Aborting.\n");
	pr_info("You can use freq_failsafe_off option to disable this check.\n");
	return -EINVAL;
	}
	if (!voltage_failsafe_off && max_voltage != current_voltage) {
	pr_info("Your processor is running at different voltage then its maximum. Aborting.\n");
	pr_info("You can use voltage_failsafe_off option to disable this check.\n");
	return -EINVAL;
	}

	/* Calc FSB speed */
	fsb = cpu_khz / current_multiplier;

	#if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
	/* Check for ACPI processor speed limit */
	if (!ignore_acpi_limit && !eps_acpi_init()) {
	if (!acpi_processor_get_bios_limit(policy->cpu, &limit)) {
	pr_info("ACPI limit %u.%uGHz\n",
	limit/1000000,
	(limit%1000000)/10000);
	eps_acpi_exit(policy);
	/* Check if max_multiplier is in BIOS limits */
	if (limit && max_multiplier * fsb > limit) {
	pr_info("Aborting\n");
	return -EINVAL;
	}
	}
	}
	#endif

	/* Allow user to set lower maximum voltage then that reported
	* by processor */
	if (brand == EPS_BRAND_C7M && set_max_voltage) {
	u32 v;

	/* Change mV to something hardware can use */
	v = (set_max_voltage - 700) / 16;
	/* Check if voltage is within limits */
	if (v >= min_voltage && v <= max_voltage) {
	pr_info("Setting %dmV as maximum\n", v * 16 + 700);
	max_voltage = v;
	}
	}

	/* Calc number of p-states supported */
	if (brand == EPS_BRAND_C7M)
	states = max_multiplier - min_multiplier + 1;
	else
	states = 2;

	/* Allocate private data and frequency table for current cpu */
	centaur = kzalloc(sizeof(*centaur)
	+ (states + 1) * sizeof(struct cpufreq_frequency_table),
	GFP_KERNEL);
	if (!centaur)
	return -ENOMEM;
	eps_cpu[0] = centaur;

	/* Copy basic values */
	centaur->fsb = fsb;
	#if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
	centaur->bios_limit = limit;
	#endif

	/* Fill frequency and MSR value table */
	f_table = &centaur->freq_table[0];
	if (brand != EPS_BRAND_C7M) {
	f_table[0].frequency = fsb * min_multiplier;
	f_table[0].driver_data = (min_multiplier << 8) \| min_voltage;
	f_table[1].frequency = fsb * max_multiplier;
	f_table[1].driver_data = (max_multiplier << 8) \| max_voltage;
	f_table[2].frequency = CPUFREQ_TABLE_END;
	} else {
	k = 0;
	step = ((max_voltage - min_voltage) * 256)
	/ (max_multiplier - min_multiplier);
	for (i = min_multiplier; i <= max_multiplier; i++) {
	voltage = (k * step) / 256 + min_voltage;
	f_table[k].frequency = fsb * i;
	f_table[k].driver_data = (i << 8) \| voltage;
	k++;
	}
	f_table[k].frequency = CPUFREQ_TABLE_END;
	}

	policy->cpuinfo.transition_latency = 140000; /* 844mV -> 700mV in ns */

	ret = cpufreq_table_validate_and_show(policy, &centaur->freq_table[0]);
	if (ret) {
	kfree(centaur);
	return ret;
	}

	return 0;
	}

	static int eps_cpu_exit(struct cpufreq_policy *policy)
	{
	unsigned int cpu = policy->cpu;

	/* Bye */
	kfree(eps_cpu[cpu]);
	eps_cpu[cpu] = NULL;
	return 0;
	}

	static struct cpufreq_driver eps_driver = {
	.verify = cpufreq_generic_frequency_table_verify,
	.target_index = eps_target,
	.init = eps_cpu_init,
	.exit = eps_cpu_exit,
	.get = eps_get,
	.name = "e_powersaver",
	.attr = cpufreq_generic_attr,
	};


	/* This driver will work only on Centaur C7 processors with
	* Enhanced SpeedStep/PowerSaver registers */
	static const struct x86_cpu_id eps_cpu_id[] = {
	{ X86_VENDOR_CENTAUR, 6, X86_MODEL_ANY, X86_FEATURE_EST },
	{}
	};
	MODULE_DEVICE_TABLE(x86cpu, eps_cpu_id);

	static int __init eps_init(void)
	{
	if (!x86_match_cpu(eps_cpu_id) \|\| boot_cpu_data.x86_model < 10)
	return -ENODEV;
	if (cpufreq_register_driver(&eps_driver))
	return -EINVAL;
	return 0;
	}

	static void __exit eps_exit(void)
	{
	cpufreq_unregister_driver(&eps_driver);
	}

	/* Allow user to overclock his machine or to change frequency to higher after
	* unloading module */
	module_param(freq_failsafe_off, int, 0644);
	MODULE_PARM_DESC(freq_failsafe_off, "Disable current vs max frequency check");
	module_param(voltage_failsafe_off, int, 0644);
	MODULE_PARM_DESC(voltage_failsafe_off, "Disable current vs max voltage check");
	#if IS_ENABLED(CONFIG_ACPI_PROCESSOR)
	module_param(ignore_acpi_limit, int, 0644);
	MODULE_PARM_DESC(ignore_acpi_limit, "Don't check ACPI's processor speed limit");
	#endif
	module_param(set_max_voltage, int, 0644);
	MODULE_PARM_DESC(set_max_voltage, "Set maximum CPU voltage (mV) C7-M only");

	MODULE_AUTHOR("Rafal Bilski <rafalbilski@interia.pl>");
	MODULE_DESCRIPTION("Enhanced PowerSaver driver for VIA C7 CPU's.");
	MODULE_LICENSE("GPL");

	module_init(eps_init);
	module_exit(eps_exit);