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acpi-cpufreq.c

/*
 * acpi-cpufreq.c - ACPI Processor P-States Driver ($Revision: 1.4 $)
 *
 *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
 *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
 *  Copyright (C) 2002 - 2004 Dominik Brodowski <linux@brodo.de>
 *  Copyright (C) 2006       Denis Sadykov <denis.m.sadykov@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; either version 2 of the License, or (at
 *  your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/sched.h>
#include <linux/cpufreq.h>
#include <linux/compiler.h>
#include <linux/dmi.h>

#include <linux/acpi.h>
#include <acpi/processor.h>

#include <asm/io.h>
#include <asm/msr.h>
#include <asm/processor.h>
#include <asm/cpufeature.h>
#include <asm/delay.h>
#include <asm/uaccess.h>

#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "acpi-cpufreq", msg)

MODULE_AUTHOR("Paul Diefenbaugh, Dominik Brodowski");
MODULE_DESCRIPTION("ACPI Processor P-States Driver");
MODULE_LICENSE("GPL");

enum {
      UNDEFINED_CAPABLE = 0,
      SYSTEM_INTEL_MSR_CAPABLE,
      SYSTEM_IO_CAPABLE,
};

#define INTEL_MSR_RANGE       (0xffff)
#define CPUID_6_ECX_APERFMPERF_CAPABILITY (0x1)

struct acpi_cpufreq_data {
      struct acpi_processor_performance *acpi_data;
      struct cpufreq_frequency_table *freq_table;
      unsigned int max_freq;
      unsigned int resume;
      unsigned int cpu_feature;
};

static struct acpi_cpufreq_data *drv_data[NR_CPUS];
/* acpi_perf_data is a pointer to percpu data. */
static struct acpi_processor_performance *acpi_perf_data;

static struct cpufreq_driver acpi_cpufreq_driver;

static unsigned int acpi_pstate_strict;

static int check_est_cpu(unsigned int cpuid)
{
      struct cpuinfo_x86 *cpu = &cpu_data(cpuid);

      if (cpu->x86_vendor != X86_VENDOR_INTEL ||
          !cpu_has(cpu, X86_FEATURE_EST))
            return 0;

      return 1;
}

static unsigned extract_io(u32 value, struct acpi_cpufreq_data *data)
{
      struct acpi_processor_performance *perf;
      int i;

      perf = data->acpi_data;

      for (i=0; i<perf->state_count; i++) {
            if (value == perf->states[i].status)
                  return data->freq_table[i].frequency;
      }
      return 0;
}

static unsigned extract_msr(u32 msr, struct acpi_cpufreq_data *data)
{
      int i;
      struct acpi_processor_performance *perf;

      msr &= INTEL_MSR_RANGE;
      perf = data->acpi_data;

      for (i=0; data->freq_table[i].frequency != CPUFREQ_TABLE_END; i++) {
            if (msr == perf->states[data->freq_table[i].index].status)
                  return data->freq_table[i].frequency;
      }
      return data->freq_table[0].frequency;
}

static unsigned extract_freq(u32 val, struct acpi_cpufreq_data *data)
{
      switch (data->cpu_feature) {
      case SYSTEM_INTEL_MSR_CAPABLE:
            return extract_msr(val, data);
      case SYSTEM_IO_CAPABLE:
            return extract_io(val, data);
      default:
            return 0;
      }
}

struct msr_addr {
      u32 reg;
};

struct io_addr {
      u16 port;
      u8 bit_width;
};

typedef union {
      struct msr_addr msr;
      struct io_addr io;
} drv_addr_union;

struct drv_cmd {
      unsigned int type;
      cpumask_t mask;
      drv_addr_union addr;
      u32 val;
};

static void do_drv_read(struct drv_cmd *cmd)
{
      u32 h;

      switch (cmd->type) {
      case SYSTEM_INTEL_MSR_CAPABLE:
            rdmsr(cmd->addr.msr.reg, cmd->val, h);
            break;
      case SYSTEM_IO_CAPABLE:
            acpi_os_read_port((acpi_io_address)cmd->addr.io.port,
                        &cmd->val,
                        (u32)cmd->addr.io.bit_width);
            break;
      default:
            break;
      }
}

static void do_drv_write(struct drv_cmd *cmd)
{
      u32 lo, hi;

      switch (cmd->type) {
      case SYSTEM_INTEL_MSR_CAPABLE:
            rdmsr(cmd->addr.msr.reg, lo, hi);
            lo = (lo & ~INTEL_MSR_RANGE) | (cmd->val & INTEL_MSR_RANGE);
            wrmsr(cmd->addr.msr.reg, lo, hi);
            break;
      case SYSTEM_IO_CAPABLE:
            acpi_os_write_port((acpi_io_address)cmd->addr.io.port,
                        cmd->val,
                        (u32)cmd->addr.io.bit_width);
            break;
      default:
            break;
      }
}

static void drv_read(struct drv_cmd *cmd)
{
      cpumask_t saved_mask = current->cpus_allowed;
      cmd->val = 0;

      set_cpus_allowed(current, cmd->mask);
      do_drv_read(cmd);
      set_cpus_allowed(current, saved_mask);
}

static void drv_write(struct drv_cmd *cmd)
{
      cpumask_t saved_mask = current->cpus_allowed;
      unsigned int i;

      for_each_cpu_mask(i, cmd->mask) {
            set_cpus_allowed(current, cpumask_of_cpu(i));
            do_drv_write(cmd);
      }

      set_cpus_allowed(current, saved_mask);
      return;
}

static u32 get_cur_val(cpumask_t mask)
{
      struct acpi_processor_performance *perf;
      struct drv_cmd cmd;

      if (unlikely(cpus_empty(mask)))
            return 0;

      switch (drv_data[first_cpu(mask)]->cpu_feature) {
      case SYSTEM_INTEL_MSR_CAPABLE:
            cmd.type = SYSTEM_INTEL_MSR_CAPABLE;
            cmd.addr.msr.reg = MSR_IA32_PERF_STATUS;
            break;
      case SYSTEM_IO_CAPABLE:
            cmd.type = SYSTEM_IO_CAPABLE;
            perf = drv_data[first_cpu(mask)]->acpi_data;
            cmd.addr.io.port = perf->control_register.address;
            cmd.addr.io.bit_width = perf->control_register.bit_width;
            break;
      default:
            return 0;
      }

      cmd.mask = mask;

      drv_read(&cmd);

      dprintk("get_cur_val = %u\n", cmd.val);

      return cmd.val;
}

/*
 * Return the measured active (C0) frequency on this CPU since last call
 * to this function.
 * Input: cpu number
 * Return: Average CPU frequency in terms of max frequency (zero on error)
 *
 * We use IA32_MPERF and IA32_APERF MSRs to get the measured performance
 * over a period of time, while CPU is in C0 state.
 * IA32_MPERF counts at the rate of max advertised frequency
 * IA32_APERF counts at the rate of actual CPU frequency
 * Only IA32_APERF/IA32_MPERF ratio is architecturally defined and
 * no meaning should be associated with absolute values of these MSRs.
 */
static unsigned int get_measured_perf(unsigned int cpu)
{
      union {
            struct {
                  u32 lo;
                  u32 hi;
            } split;
            u64 whole;
      } aperf_cur, mperf_cur;

      cpumask_t saved_mask;
      unsigned int perf_percent;
      unsigned int retval;

      saved_mask = current->cpus_allowed;
      set_cpus_allowed(current, cpumask_of_cpu(cpu));
      if (get_cpu() != cpu) {
            /* We were not able to run on requested processor */
            put_cpu();
            return 0;
      }

      rdmsr(MSR_IA32_APERF, aperf_cur.split.lo, aperf_cur.split.hi);
      rdmsr(MSR_IA32_MPERF, mperf_cur.split.lo, mperf_cur.split.hi);

      wrmsr(MSR_IA32_APERF, 0,0);
      wrmsr(MSR_IA32_MPERF, 0,0);

#ifdef __i386__
      /*
       * We dont want to do 64 bit divide with 32 bit kernel
       * Get an approximate value. Return failure in case we cannot get
       * an approximate value.
       */
      if (unlikely(aperf_cur.split.hi || mperf_cur.split.hi)) {
            int shift_count;
            u32 h;

            h = max_t(u32, aperf_cur.split.hi, mperf_cur.split.hi);
            shift_count = fls(h);

            aperf_cur.whole >>= shift_count;
            mperf_cur.whole >>= shift_count;
      }

      if (((unsigned long)(-1) / 100) < aperf_cur.split.lo) {
            int shift_count = 7;
            aperf_cur.split.lo >>= shift_count;
            mperf_cur.split.lo >>= shift_count;
      }

      if (aperf_cur.split.lo && mperf_cur.split.lo)
            perf_percent = (aperf_cur.split.lo * 100) / mperf_cur.split.lo;
      else
            perf_percent = 0;

#else
      if (unlikely(((unsigned long)(-1) / 100) < aperf_cur.whole)) {
            int shift_count = 7;
            aperf_cur.whole >>= shift_count;
            mperf_cur.whole >>= shift_count;
      }

      if (aperf_cur.whole && mperf_cur.whole)
            perf_percent = (aperf_cur.whole * 100) / mperf_cur.whole;
      else
            perf_percent = 0;

#endif

      retval = drv_data[cpu]->max_freq * perf_percent / 100;

      put_cpu();
      set_cpus_allowed(current, saved_mask);

      dprintk("cpu %d: performance percent %d\n", cpu, perf_percent);
      return retval;
}

static unsigned int get_cur_freq_on_cpu(unsigned int cpu)
{
      struct acpi_cpufreq_data *data = drv_data[cpu];
      unsigned int freq;

      dprintk("get_cur_freq_on_cpu (%d)\n", cpu);

      if (unlikely(data == NULL ||
                 data->acpi_data == NULL || data->freq_table == NULL)) {
            return 0;
      }

      freq = extract_freq(get_cur_val(cpumask_of_cpu(cpu)), data);
      dprintk("cur freq = %u\n", freq);

      return freq;
}

static unsigned int check_freqs(cpumask_t mask, unsigned int freq,
                        struct acpi_cpufreq_data *data)
{
      unsigned int cur_freq;
      unsigned int i;

      for (i=0; i<100; i++) {
            cur_freq = extract_freq(get_cur_val(mask), data);
            if (cur_freq == freq)
                  return 1;
            udelay(10);
      }
      return 0;
}

static int acpi_cpufreq_target(struct cpufreq_policy *policy,
                         unsigned int target_freq, unsigned int relation)
{
      struct acpi_cpufreq_data *data = drv_data[policy->cpu];
      struct acpi_processor_performance *perf;
      struct cpufreq_freqs freqs;
      cpumask_t online_policy_cpus;
      struct drv_cmd cmd;
      unsigned int next_state = 0; /* Index into freq_table */
      unsigned int next_perf_state = 0; /* Index into perf table */
      unsigned int i;
      int result = 0;

      dprintk("acpi_cpufreq_target %d (%d)\n", target_freq, policy->cpu);

      if (unlikely(data == NULL ||
           data->acpi_data == NULL || data->freq_table == NULL)) {
            return -ENODEV;
      }

      perf = data->acpi_data;
      result = cpufreq_frequency_table_target(policy,
                                    data->freq_table,
                                    target_freq,
                                    relation, &next_state);
      if (unlikely(result))
            return -ENODEV;

#ifdef CONFIG_HOTPLUG_CPU
      /* cpufreq holds the hotplug lock, so we are safe from here on */
      cpus_and(online_policy_cpus, cpu_online_map, policy->cpus);
#else
      online_policy_cpus = policy->cpus;
#endif

      next_perf_state = data->freq_table[next_state].index;
      if (perf->state == next_perf_state) {
            if (unlikely(data->resume)) {
                  dprintk("Called after resume, resetting to P%d\n",
                        next_perf_state);
                  data->resume = 0;
            } else {
                  dprintk("Already at target state (P%d)\n",
                        next_perf_state);
                  return 0;
            }
      }

      switch (data->cpu_feature) {
      case SYSTEM_INTEL_MSR_CAPABLE:
            cmd.type = SYSTEM_INTEL_MSR_CAPABLE;
            cmd.addr.msr.reg = MSR_IA32_PERF_CTL;
            cmd.val = (u32) perf->states[next_perf_state].control;
            break;
      case SYSTEM_IO_CAPABLE:
            cmd.type = SYSTEM_IO_CAPABLE;
            cmd.addr.io.port = perf->control_register.address;
            cmd.addr.io.bit_width = perf->control_register.bit_width;
            cmd.val = (u32) perf->states[next_perf_state].control;
            break;
      default:
            return -ENODEV;
      }

      cpus_clear(cmd.mask);

      if (policy->shared_type != CPUFREQ_SHARED_TYPE_ANY)
            cmd.mask = online_policy_cpus;
      else
            cpu_set(policy->cpu, cmd.mask);

      freqs.old = perf->states[perf->state].core_frequency * 1000;
      freqs.new = data->freq_table[next_state].frequency;
      for_each_cpu_mask(i, cmd.mask) {
            freqs.cpu = i;
            cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
      }

      drv_write(&cmd);

      if (acpi_pstate_strict) {
            if (!check_freqs(cmd.mask, freqs.new, data)) {
                  dprintk("acpi_cpufreq_target failed (%d)\n",
                        policy->cpu);
                  return -EAGAIN;
            }
      }

      for_each_cpu_mask(i, cmd.mask) {
            freqs.cpu = i;
            cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
      }
      perf->state = next_perf_state;

      return result;
}

static int acpi_cpufreq_verify(struct cpufreq_policy *policy)
{
      struct acpi_cpufreq_data *data = drv_data[policy->cpu];

      dprintk("acpi_cpufreq_verify\n");

      return cpufreq_frequency_table_verify(policy, data->freq_table);
}

static unsigned long
acpi_cpufreq_guess_freq(struct acpi_cpufreq_data *data, unsigned int cpu)
{
      struct acpi_processor_performance *perf = data->acpi_data;

      if (cpu_khz) {
            /* search the closest match to cpu_khz */
            unsigned int i;
            unsigned long freq;
            unsigned long freqn = perf->states[0].core_frequency * 1000;

            for (i=0; i<(perf->state_count-1); i++) {
                  freq = freqn;
                  freqn = perf->states[i+1].core_frequency * 1000;
                  if ((2 * cpu_khz) > (freqn + freq)) {
                        perf->state = i;
                        return freq;
                  }
            }
            perf->state = perf->state_count-1;
            return freqn;
      } else {
            /* assume CPU is at P0... */
            perf->state = 0;
            return perf->states[0].core_frequency * 1000;
      }
}

/*
 * acpi_cpufreq_early_init - initialize ACPI P-States library
 *
 * Initialize the ACPI P-States library (drivers/acpi/processor_perflib.c)
 * in order to determine correct frequency and voltage pairings. We can
 * do _PDC and _PSD and find out the processor dependency for the
 * actual init that will happen later...
 */
static int __init acpi_cpufreq_early_init(void)
{
      dprintk("acpi_cpufreq_early_init\n");

      acpi_perf_data = alloc_percpu(struct acpi_processor_performance);
      if (!acpi_perf_data) {
            dprintk("Memory allocation error for acpi_perf_data.\n");
            return -ENOMEM;
      }

      /* Do initialization in ACPI core */
      acpi_processor_preregister_performance(acpi_perf_data);
      return 0;
}

#ifdef CONFIG_SMP
/*
 * Some BIOSes do SW_ANY coordination internally, either set it up in hw
 * or do it in BIOS firmware and won't inform about it to OS. If not
 * detected, this has a side effect of making CPU run at a different speed
 * than OS intended it to run at. Detect it and handle it cleanly.
 */
static int bios_with_sw_any_bug;

static int sw_any_bug_found(const struct dmi_system_id *d)
{
      bios_with_sw_any_bug = 1;
      return 0;
}

static const struct dmi_system_id sw_any_bug_dmi_table[] = {
      {
            .callback = sw_any_bug_found,
            .ident = "Supermicro Server X6DLP",
            .matches = {
                  DMI_MATCH(DMI_SYS_VENDOR, "Supermicro"),
                  DMI_MATCH(DMI_BIOS_VERSION, "080010"),
                  DMI_MATCH(DMI_PRODUCT_NAME, "X6DLP"),
            },
      },
      { }
};
#endif

static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
      unsigned int i;
      unsigned int valid_states = 0;
      unsigned int cpu = policy->cpu;
      struct acpi_cpufreq_data *data;
      unsigned int result = 0;
      struct cpuinfo_x86 *c = &cpu_data(policy->cpu);
      struct acpi_processor_performance *perf;

      dprintk("acpi_cpufreq_cpu_init\n");

      data = kzalloc(sizeof(struct acpi_cpufreq_data), GFP_KERNEL);
      if (!data)
            return -ENOMEM;

      data->acpi_data = percpu_ptr(acpi_perf_data, cpu);
      drv_data[cpu] = data;

      if (cpu_has(c, X86_FEATURE_CONSTANT_TSC))
            acpi_cpufreq_driver.flags |= CPUFREQ_CONST_LOOPS;

      result = acpi_processor_register_performance(data->acpi_data, cpu);
      if (result)
            goto err_free;

      perf = data->acpi_data;
      policy->shared_type = perf->shared_type;

      /*
       * Will let policy->cpus know about dependency only when software
       * coordination is required.
       */
      if (policy->shared_type == CPUFREQ_SHARED_TYPE_ALL ||
          policy->shared_type == CPUFREQ_SHARED_TYPE_ANY) {
            policy->cpus = perf->shared_cpu_map;
      }

#ifdef CONFIG_SMP
      dmi_check_system(sw_any_bug_dmi_table);
      if (bios_with_sw_any_bug && cpus_weight(policy->cpus) == 1) {
            policy->shared_type = CPUFREQ_SHARED_TYPE_ALL;
            policy->cpus = per_cpu(cpu_core_map, cpu);
      }
#endif

      /* capability check */
      if (perf->state_count <= 1) {
            dprintk("No P-States\n");
            result = -ENODEV;
            goto err_unreg;
      }

      if (perf->control_register.space_id != perf->status_register.space_id) {
            result = -ENODEV;
            goto err_unreg;
      }

      switch (perf->control_register.space_id) {
      case ACPI_ADR_SPACE_SYSTEM_IO:
            dprintk("SYSTEM IO addr space\n");
            data->cpu_feature = SYSTEM_IO_CAPABLE;
            break;
      case ACPI_ADR_SPACE_FIXED_HARDWARE:
            dprintk("HARDWARE addr space\n");
            if (!check_est_cpu(cpu)) {
                  result = -ENODEV;
                  goto err_unreg;
            }
            data->cpu_feature = SYSTEM_INTEL_MSR_CAPABLE;
            break;
      default:
            dprintk("Unknown addr space %d\n",
                  (u32) (perf->control_register.space_id));
            result = -ENODEV;
            goto err_unreg;
      }

      data->freq_table = kmalloc(sizeof(struct cpufreq_frequency_table) *
                (perf->state_count+1), GFP_KERNEL);
      if (!data->freq_table) {
            result = -ENOMEM;
            goto err_unreg;
      }

      /* detect transition latency */
      policy->cpuinfo.transition_latency = 0;
      for (i=0; i<perf->state_count; i++) {
            if ((perf->states[i].transition_latency * 1000) >
                policy->cpuinfo.transition_latency)
                  policy->cpuinfo.transition_latency =
                      perf->states[i].transition_latency * 1000;
      }

      data->max_freq = perf->states[0].core_frequency * 1000;
      /* table init */
      for (i=0; i<perf->state_count; i++) {
            if (i>0 && perf->states[i].core_frequency >=
                data->freq_table[valid_states-1].frequency / 1000)
                  continue;

            data->freq_table[valid_states].index = i;
            data->freq_table[valid_states].frequency =
                perf->states[i].core_frequency * 1000;
            valid_states++;
      }
      data->freq_table[valid_states].frequency = CPUFREQ_TABLE_END;
      perf->state = 0;

      result = cpufreq_frequency_table_cpuinfo(policy, data->freq_table);
      if (result)
            goto err_freqfree;

      switch (perf->control_register.space_id) {
      case ACPI_ADR_SPACE_SYSTEM_IO:
            /* Current speed is unknown and not detectable by IO port */
            policy->cur = acpi_cpufreq_guess_freq(data, policy->cpu);
            break;
      case ACPI_ADR_SPACE_FIXED_HARDWARE:
            acpi_cpufreq_driver.get = get_cur_freq_on_cpu;
            policy->cur = get_cur_freq_on_cpu(cpu);
            break;
      default:
            break;
      }

      /* notify BIOS that we exist */
      acpi_processor_notify_smm(THIS_MODULE);

      /* Check for APERF/MPERF support in hardware */
      if (c->x86_vendor == X86_VENDOR_INTEL && c->cpuid_level >= 6) {
            unsigned int ecx;
            ecx = cpuid_ecx(6);
            if (ecx & CPUID_6_ECX_APERFMPERF_CAPABILITY)
                  acpi_cpufreq_driver.getavg = get_measured_perf;
      }

      dprintk("CPU%u - ACPI performance management activated.\n", cpu);
      for (i = 0; i < perf->state_count; i++)
            dprintk("     %cP%d: %d MHz, %d mW, %d uS\n",
                  (i == perf->state ? '*' : ' '), i,
                  (u32) perf->states[i].core_frequency,
                  (u32) perf->states[i].power,
                  (u32) perf->states[i].transition_latency);

      cpufreq_frequency_table_get_attr(data->freq_table, policy->cpu);

      /*
       * the first call to ->target() should result in us actually
       * writing something to the appropriate registers.
       */
      data->resume = 1;

      return result;

err_freqfree:
      kfree(data->freq_table);
err_unreg:
      acpi_processor_unregister_performance(perf, cpu);
err_free:
      kfree(data);
      drv_data[cpu] = NULL;

      return result;
}

static int acpi_cpufreq_cpu_exit(struct cpufreq_policy *policy)
{
      struct acpi_cpufreq_data *data = drv_data[policy->cpu];

      dprintk("acpi_cpufreq_cpu_exit\n");

      if (data) {
            cpufreq_frequency_table_put_attr(policy->cpu);
            drv_data[policy->cpu] = NULL;
            acpi_processor_unregister_performance(data->acpi_data,
                                          policy->cpu);
            kfree(data);
      }

      return 0;
}

static int acpi_cpufreq_resume(struct cpufreq_policy *policy)
{
      struct acpi_cpufreq_data *data = drv_data[policy->cpu];

      dprintk("acpi_cpufreq_resume\n");

      data->resume = 1;

      return 0;
}

static struct freq_attr *acpi_cpufreq_attr[] = {
      &cpufreq_freq_attr_scaling_available_freqs,
      NULL,
};

static struct cpufreq_driver acpi_cpufreq_driver = {
      .verify = acpi_cpufreq_verify,
      .target = acpi_cpufreq_target,
      .init = acpi_cpufreq_cpu_init,
      .exit = acpi_cpufreq_cpu_exit,
      .resume = acpi_cpufreq_resume,
      .name = "acpi-cpufreq",
      .owner = THIS_MODULE,
      .attr = acpi_cpufreq_attr,
};

static int __init acpi_cpufreq_init(void)
{
      int ret;

      dprintk("acpi_cpufreq_init\n");

      ret = acpi_cpufreq_early_init();
      if (ret)
            return ret;

      return cpufreq_register_driver(&acpi_cpufreq_driver);
}

static void __exit acpi_cpufreq_exit(void)
{
      dprintk("acpi_cpufreq_exit\n");

      cpufreq_unregister_driver(&acpi_cpufreq_driver);

      free_percpu(acpi_perf_data);

      return;
}

module_param(acpi_pstate_strict, uint, 0644);
MODULE_PARM_DESC(acpi_pstate_strict,
      "value 0 or non-zero. non-zero -> strict ACPI checks are "
      "performed during frequency changes.");

late_initcall(acpi_cpufreq_init);
module_exit(acpi_cpufreq_exit);

MODULE_ALIAS("acpi");

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