cpufreq.c

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/*
 * 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 <linux/export.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 unsigned int ref_freq;
static unsigned long    loops_per_jiffy_ref;

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;

    if (!ref_freq) {
        ref_freq = freqs.old;
        loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
    }

    cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
    if (freqs.old < freqs.new)
        boot_cpu_data.loops_per_jiffy = cpufreq_scale(
                loops_per_jiffy_ref, ref_freq, freqs.new);
    clk_set_rate(cpuclk, freq);
    if (freqs.new < freqs.old)
        boot_cpu_data.loops_per_jiffy = cpufreq_scale(
                loops_per_jiffy_ref, ref_freq, freqs.new);
    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;

    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);
}
late_initcall(at32_cpufreq_init);