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e_powersaver.c

/*
 *  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 <asm/msr.h>
#include <asm/tsc.h>
#include <asm/timex.h>
#include <asm/io.h>
#include <asm/delay.h>

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

struct eps_cpu_data {
      u32 fsb;
      struct cpufreq_frequency_table freq_table[];
};

static struct eps_cpu_data *eps_cpu[NR_CPUS];


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);

      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!\n");
      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;
      u32 fsb;
      struct eps_cpu_data *centaur;
      struct cpufreq_frequency_table *f_table;
      int k, step, voltage;
      int ret;
      int states;

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

      /* Check brand */
      printk("eps: Detected VIA ");
      rdmsr(0x1153, lo, hi);
      brand = (((lo >> 2) ^ lo) >> 18) & 3;
      switch(brand) {
      case EPS_BRAND_C7M:
            printk("C7-M\n");
            break;
      case EPS_BRAND_C7:
            printk("C7\n");
            break;
      case EPS_BRAND_EDEN:
            printk("Eden\n");
            break;
      case EPS_BRAND_C3:
            printk("C3\n");
            return -ENODEV;
            break;
      }
      /* Enable Enhanced PowerSaver */
      rdmsrl(MSR_IA32_MISC_ENABLE, val);
      if (!(val & 1 << 16)) {
            val |= 1 << 16;
            wrmsrl(MSR_IA32_MISC_ENABLE, val);
            /* Can be locked at 0 */
            rdmsrl(MSR_IA32_MISC_ENABLE, val);
            if (!(val & 1 << 16)) {
                  printk("eps: Can't enable Enhanced PowerSaver\n");
                  return -ENODEV;
            }
      }

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

      /* Print limits */
      max_voltage = hi & 0xff;
      printk("eps: Highest voltage = %dmV\n", max_voltage * 16 + 700);
      max_multiplier = (hi >> 8) & 0xff;
      printk("eps: Highest multiplier = %d\n", max_multiplier);
      min_voltage = (hi >> 16) & 0xff;
      printk("eps: Lowest voltage = %dmV\n", min_voltage * 16 + 700);
      min_multiplier = (hi >> 24) & 0xff;
      printk("eps: 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 > 0x1c || max_voltage > 0x1c)
            return -EINVAL;
      if (max_voltage < min_voltage)
            return -EINVAL;

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

      /* 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;
      struct eps_cpu_data *centaur;
      u32 lo, hi;

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

      /* Get max frequency */
      rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
      /* Set max frequency */
      eps_set_state(centaur, cpu, hi & 0xffff);
      /* 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);
}

MODULE_AUTHOR("Rafał 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);

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