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

  #if defined CONFIG_ACPI_PROCESSOR || defined CONFIG_ACPI_PROCESSOR_MODULE
  #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 defined CONFIG_ACPI_PROCESSOR || defined CONFIG_ACPI_PROCESSOR_MODULE
  	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 defined CONFIG_ACPI_PROCESSOR || defined CONFIG_ACPI_PROCESSOR_MODULE
  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(struct acpi_processor_performance),
  				      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(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 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,
  			 unsigned int cpu,
  			 u32 dest_state)
  {
  	struct cpufreq_freqs freqs;
  	u32 lo, hi;
  	int err = 0;
  	int i;
  
  	freqs.old = eps_get(cpu);
  	freqs.new = centaur->fsb * ((dest_state >> 8) & 0xff);
  	freqs.cpu = cpu;
  	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
  
  	/* 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)) {
  			err = -ENODEV;
  			goto postchange;
  		}
  	}
  	/* 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)) {
  			err = -ENODEV;
  			goto postchange;
  		}
  	} while (lo & ((1 << 16) | (1 << 17)));
  
  	/* Return current frequency */
  postchange:
  	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
  	freqs.new = centaur->fsb * ((lo >> 8) & 0xff);

  #ifdef DEBUG
  	{
  	u8 current_multiplier, current_voltage;

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

  	}
  #endif

  	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
  	return err;
  }
  
  static int eps_target(struct cpufreq_policy *policy,
  			       unsigned int target_freq,
  			       unsigned int relation)
  {
  	struct eps_cpu_data *centaur;
  	unsigned int newstate = 0;
  	unsigned int cpu = policy->cpu;
  	unsigned int dest_state;
  	int ret;
  
  	if (unlikely(eps_cpu[cpu] == NULL))
  		return -ENODEV;
  	centaur = eps_cpu[cpu];
  
  	if (unlikely(cpufreq_frequency_table_target(policy,
  			&eps_cpu[cpu]->freq_table[0],
  			target_freq,
  			relation,
  			&newstate))) {
  		return -EINVAL;
  	}
  
  	/* Make frequency transition */
  	dest_state = centaur->freq_table[newstate].index & 0xffff;
  	ret = eps_set_state(centaur, cpu, dest_state);
  	if (ret)
  		printk(KERN_ERR "eps: Timeout!
  ");
  	return ret;
  }
  
  static int eps_verify(struct cpufreq_policy *policy)
  {
  	return cpufreq_frequency_table_verify(policy,
  			&eps_cpu[policy->cpu]->freq_table[0]);
  }
  
  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 defined CONFIG_ACPI_PROCESSOR || defined CONFIG_ACPI_PROCESSOR_MODULE
  	unsigned int limit;
  #endif

  
  	if (policy->cpu != 0)
  		return -ENODEV;
  
  	/* Check brand */

  	printk(KERN_INFO "eps: Detected VIA ");

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

  	switch (brand) {

  	case EPS_BRAND_C7M:

  		printk(KERN_CONT "C7-M
  ");

  		break;
  	case EPS_BRAND_C7:

  		printk(KERN_CONT "C7
  ");

  		break;
  	case EPS_BRAND_EDEN:

  		printk(KERN_CONT "Eden
  ");

  		break;

  	case EPS_BRAND_C7D:
  		printk(KERN_CONT "C7-D
  ");
  		break;

  	case EPS_BRAND_C3:

  		printk(KERN_CONT "C3
  ");

  		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)) {

  			printk(KERN_INFO "eps: Can't enable Enhanced PowerSaver
  ");

  			return -ENODEV;
  		}
  	}
  
  	/* Print voltage and multiplier */
  	rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
  	current_voltage = lo & 0xff;

  	printk(KERN_INFO "eps: Current voltage = %dmV
  ",
  			current_voltage * 16 + 700);

  	current_multiplier = (lo >> 8) & 0xff;

  	printk(KERN_INFO "eps: Current multiplier = %d
  ", current_multiplier);

  
  	/* Print limits */
  	max_voltage = hi & 0xff;

  	printk(KERN_INFO "eps: Highest voltage = %dmV
  ",
  			max_voltage * 16 + 700);

  	max_multiplier = (hi >> 8) & 0xff;

  	printk(KERN_INFO "eps: Highest multiplier = %d
  ", max_multiplier);

  	min_voltage = (hi >> 16) & 0xff;

  	printk(KERN_INFO "eps: Lowest voltage = %dmV
  ",
  			min_voltage * 16 + 700);

  	min_multiplier = (hi >> 24) & 0xff;

  	printk(KERN_INFO "eps: Lowest multiplier = %d
  ", 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) {
  		printk(KERN_INFO "eps: Your processor is running at different "
  			"frequency then its maximum. Aborting.
  ");
  		printk(KERN_INFO "eps: You can use freq_failsafe_off option "
  			"to disable this check.
  ");
  		return -EINVAL;
  	}
  	if (!voltage_failsafe_off && max_voltage != current_voltage) {
  		printk(KERN_INFO "eps: Your processor is running at different "
  			"voltage then its maximum. Aborting.
  ");
  		printk(KERN_INFO "eps: You can use voltage_failsafe_off "
  			"option to disable this check.
  ");
  		return -EINVAL;
  	}

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

  
  #if defined CONFIG_ACPI_PROCESSOR || defined CONFIG_ACPI_PROCESSOR_MODULE
  	/* Check for ACPI processor speed limit */
  	if (!ignore_acpi_limit && !eps_acpi_init()) {
  		if (!acpi_processor_get_bios_limit(policy->cpu, &limit)) {
  			printk(KERN_INFO "eps: ACPI limit %u.%uGHz
  ",
  				limit/1000000,
  				(limit%1000000)/10000);
  			eps_acpi_exit(policy);
  			/* Check if max_multiplier is in BIOS limits */
  			if (limit && max_multiplier * fsb > limit) {
  				printk(KERN_INFO "eps: Aborting.
  ");
  				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) {
  			printk(KERN_INFO "eps: Setting %dmV as maximum.
  ",
  				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(struct eps_cpu_data)
  		    + (states + 1) * sizeof(struct cpufreq_frequency_table),
  		    GFP_KERNEL);
  	if (!centaur)
  		return -ENOMEM;
  	eps_cpu[0] = centaur;
  
  	/* Copy basic values */
  	centaur->fsb = fsb;

  #if defined CONFIG_ACPI_PROCESSOR || defined CONFIG_ACPI_PROCESSOR_MODULE
  	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].index = (min_multiplier << 8) | min_voltage;
  		f_table[1].frequency = fsb * max_multiplier;
  		f_table[1].index = (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].index = (i << 8) | voltage;
  			k++;
  		}
  		f_table[k].frequency = CPUFREQ_TABLE_END;
  	}

  	policy->cpuinfo.transition_latency = 140000; /* 844mV -> 700mV in ns */
  	policy->cur = fsb * current_multiplier;
  
  	ret = cpufreq_frequency_table_cpuinfo(policy, &centaur->freq_table[0]);
  	if (ret) {
  		kfree(centaur);
  		return ret;
  	}
  
  	cpufreq_frequency_table_get_attr(&centaur->freq_table[0], policy->cpu);
  	return 0;
  }
  
  static int eps_cpu_exit(struct cpufreq_policy *policy)
  {
  	unsigned int cpu = policy->cpu;

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

  static struct freq_attr *eps_attr[] = {

  	&cpufreq_freq_attr_scaling_available_freqs,
  	NULL,
  };

  static struct cpufreq_driver eps_driver = {

  	.verify		= eps_verify,
  	.target		= eps_target,
  	.init		= eps_cpu_init,
  	.exit		= eps_cpu_exit,
  	.get		= eps_get,
  	.name		= "e_powersaver",
  	.owner		= THIS_MODULE,
  	.attr		= eps_attr,
  };
  
  static int __init eps_init(void)
  {

  	struct cpuinfo_x86 *c = &cpu_data(0);

  
  	/* This driver will work only on Centaur C7 processors with
  	 * Enhanced SpeedStep/PowerSaver registers */
  	if (c->x86_vendor != X86_VENDOR_CENTAUR

  	    || c->x86 != 6 || c->x86_model < 10)

  		return -ENODEV;
  	if (!cpu_has(c, X86_FEATURE_EST))
  		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 defined CONFIG_ACPI_PROCESSOR || defined CONFIG_ACPI_PROCESSOR_MODULE
  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);