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cpufreq.c

/*
 * Copyright (C) 2004-2007 Atmel Corporation
 *
 * Based on MIPS implementation arch/mips/kernel/time.c
 *   Copyright 2001 MontaVista Software Inc.
 *
 * 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 DEBUG*/

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <asm/system.h>

static struct clk *cpuclk;

static int at32_verify_speed(struct cpufreq_policy *policy)
{
      if (policy->cpu != 0)
            return -EINVAL;

      cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
                  policy->cpuinfo.max_freq);
      return 0;
}

static unsigned int at32_get_speed(unsigned int cpu)
{
      /* No SMP support */
      if (cpu)
            return 0;
      return (unsigned int)((clk_get_rate(cpuclk) + 500) / 1000);
}

static int at32_set_target(struct cpufreq_policy *policy,
                    unsigned int target_freq,
                    unsigned int relation)
{
      struct cpufreq_freqs freqs;
      long freq;

      /* Convert target_freq from kHz to Hz */
      freq = clk_round_rate(cpuclk, target_freq * 1000);

      /* Check if policy->min <= new_freq <= policy->max */
      if(freq < (policy->min * 1000) || freq > (policy->max * 1000))
            return -EINVAL;

      pr_debug("cpufreq: requested frequency %u Hz\n", target_freq * 1000);

      freqs.old = at32_get_speed(0);
      freqs.new = (freq + 500) / 1000;
      freqs.cpu = 0;
      freqs.flags = 0;

      cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
      clk_set_rate(cpuclk, freq);
      cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

      pr_debug("cpufreq: set frequency %lu Hz\n", freq);

      return 0;
}

static int __init at32_cpufreq_driver_init(struct cpufreq_policy *policy)
{
      if (policy->cpu != 0)
            return -EINVAL;

      cpuclk = clk_get(NULL, "cpu");
      if (IS_ERR(cpuclk)) {
            pr_debug("cpufreq: could not get CPU clk\n");
            return PTR_ERR(cpuclk);
      }

      policy->cpuinfo.min_freq = (clk_round_rate(cpuclk, 1) + 500) / 1000;
      policy->cpuinfo.max_freq = (clk_round_rate(cpuclk, ~0UL) + 500) / 1000;
      policy->cpuinfo.transition_latency = 0;
      policy->cur = at32_get_speed(0);
      policy->min = policy->cpuinfo.min_freq;
      policy->max = policy->cpuinfo.max_freq;
      policy->governor = CPUFREQ_DEFAULT_GOVERNOR;

      printk("cpufreq: AT32AP CPU frequency driver\n");

      return 0;
}

static struct cpufreq_driver at32_driver = {
      .name       = "at32ap",
      .owner            = THIS_MODULE,
      .init       = at32_cpufreq_driver_init,
      .verify           = at32_verify_speed,
      .target           = at32_set_target,
      .get        = at32_get_speed,
      .flags            = CPUFREQ_STICKY,
};

static int __init at32_cpufreq_init(void)
{
      return cpufreq_register_driver(&at32_driver);
}

arch_initcall(at32_cpufreq_init);

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