linux-kernel-freqtable.c

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本文详细介绍了Linux中用于处理CPU频率表的辅助函数，包括CPU信息读取、验证、目标频率寻找等功能。

/*
* linux/drivers/cpufreq/freq_table.c
*
* Copyright (C) 2002 - 2003 Dominik Brodowski
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/cpufreq.h>

/*********************************************************************
* FREQUENCY TABLE HELPERS *
*********************************************************************/

int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
struct cpufreq_frequency_table *table)
{
unsigned int min_freq = ~0;
unsigned int max_freq = 0;
unsigned int i;

for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
  unsigned int freq = table[i].frequency;
  if (freq == CPUFREQ_ENTRY_INVALID) {
   pr_debug("table entry %u is invalid, skipping\n", i);

   continue;
  }
  pr_debug("table entry %u: %u kHz, %u index\n",
     i, freq, table[i].index);
  if (freq < min_freq)
   min_freq = freq;
  if (freq > max_freq)
   max_freq = freq;
}

policy->min = policy->cpuinfo.min_freq = min_freq;
policy->max = policy->cpuinfo.max_freq = max_freq;

if (policy->min == ~0)
return -EINVAL;
else
return 0;
}
EXPORT_SYMBOL_GPL(cpufreq_frequency_table_cpuinfo);

int cpufreq_frequency_table_verify(struct cpufreq_policy *policy,
struct cpufreq_frequency_table *table)
{
unsigned int next_larger = ~0;
unsigned int i;
unsigned int count = 0;

pr_debug("request for verification of policy (%u - %u kHz) for cpu %u\n",
policy->min, policy->max, policy->cpu);

cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
policy->cpuinfo.max_freq);

for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
  unsigned int freq = table[i].frequency;
  if (freq == CPUFREQ_ENTRY_INVALID)
   continue;
  if ((freq >= policy->min) && (freq <= policy->max))
   count++;
  else if ((next_larger > freq) && (freq > policy->max))
   next_larger = freq;
}

if (!count)
policy->max = next_larger;

cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
policy->cpuinfo.max_freq);

pr_debug("verification lead to (%u - %u kHz) for cpu %u\n",
policy->min, policy->max, policy->cpu);

return 0;
}
EXPORT_SYMBOL_GPL(cpufreq_frequency_table_verify);

int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
       struct cpufreq_frequency_table *table,
       unsigned int target_freq,
       unsigned int relation,
       unsigned int *index)
{
struct cpufreq_frequency_table optimal = {
  .index = ~0,
  .frequency = 0,
};
struct cpufreq_frequency_table suboptimal = {
  .index = ~0,
  .frequency = 0,
};
unsigned int i;

pr_debug("request for target %u kHz (relation: %u) for cpu %u\n",
target_freq, relation, policy->cpu);

switch (relation) {
case CPUFREQ_RELATION_H:
  suboptimal.frequency = ~0;
  break;
case CPUFREQ_RELATION_L:
  optimal.frequency = ~0;
  break;
}

for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
  unsigned int freq = table[i].frequency;
  if (freq == CPUFREQ_ENTRY_INVALID)
   continue;
  if ((freq < policy->min) || (freq > policy->max))
   continue;
  switch (relation) {
  case CPUFREQ_RELATION_H:
   if (freq <= target_freq) {
    if (freq >= optimal.frequency) {
     optimal.frequency = freq;
     optimal.index = i;
    }
   } else {
    if (freq <= suboptimal.frequency) {
     suboptimal.frequency = freq;
     suboptimal.index = i;
    }
   }
   break;
  case CPUFREQ_RELATION_L:
   if (freq >= target_freq) {
    if (freq <= optimal.frequency) {
     optimal.frequency = freq;
     optimal.index = i;
    }
   } else {
    if (freq >= suboptimal.frequency) {
     suboptimal.frequency = freq;
     suboptimal.index = i;
    }
   }
   break;
  }
}
if (optimal.index > i) {
  if (suboptimal.index > i)
   return -EINVAL;
  *index = suboptimal.index;
} else
  *index = optimal.index;

pr_debug("target is %u (%u kHz, %u)\n", *index, table[*index].frequency,
table[*index].index);

return 0;
}
EXPORT_SYMBOL_GPL(cpufreq_frequency_table_target);

static DEFINE_PER_CPU(struct cpufreq_frequency_table *, cpufreq_show_table);
/**
* show_available_freqs - show available frequencies for the specified CPU
*/
static ssize_t show_available_freqs(struct cpufreq_policy *policy, char *buf)
{
unsigned int i = 0;
unsigned int cpu = policy->cpu;
ssize_t count = 0;
struct cpufreq_frequency_table *table;

if (!per_cpu(cpufreq_show_table, cpu))
return -ENODEV;

table = per_cpu(cpufreq_show_table, cpu);

for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
  if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
   continue;
  count += sprintf(&buf[count], "%d ", table[i].frequency);
}
count += sprintf(&buf[count], "\n");

return count;

}

struct freq_attr cpufreq_freq_attr_scaling_available_freqs = {
.attr = { .name = "scaling_available_frequencies",
.mode = 0444,
},
.show = show_available_freqs,
};
EXPORT_SYMBOL_GPL(cpufreq_freq_attr_scaling_available_freqs);

/*
* if you use these, you must assure that the frequency table is valid
* all the time between get_attr and put_attr!
*/
void cpufreq_frequency_table_get_attr(struct cpufreq_frequency_table *table,
unsigned int cpu)
{
pr_debug("setting show_table for cpu %u to %p\n", cpu, table);
per_cpu(cpufreq_show_table, cpu) = table;
}
EXPORT_SYMBOL_GPL(cpufreq_frequency_table_get_attr);

void cpufreq_frequency_table_put_attr(unsigned int cpu)
{
pr_debug("clearing show_table for cpu %u\n", cpu);
per_cpu(cpufreq_show_table, cpu) = NULL;
}
EXPORT_SYMBOL_GPL(cpufreq_frequency_table_put_attr);

void cpufreq_frequency_table_update_policy_cpu(struct cpufreq_policy *policy)
{
pr_debug("Updating show_table for new_cpu %u from last_cpu %u\n",
policy->cpu, policy->last_cpu);
per_cpu(cpufreq_show_table, policy->cpu) = per_cpu(cpufreq_show_table,
policy->last_cpu);
per_cpu(cpufreq_show_table, policy->last_cpu) = NULL;
}

struct cpufreq_frequency_table *cpufreq_frequency_get_table(unsigned int cpu)
{
return per_cpu(cpufreq_show_table, cpu);
}
EXPORT_SYMBOL_GPL(cpufreq_frequency_get_table);

MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
MODULE_DESCRIPTION("CPUfreq frequency table helpers");
MODULE_LICENSE("GPL");