cpufreq.c

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/*
 * Copyright (C) 2010 Freescale Semiconductor, Inc. All Rights Reserved.
 */

/*
 * The code contained herein is licensed under the GNU General Public
 * License. You may obtain a copy of the GNU General Public License
 * Version 2 or later at the following locations:
 *
 * http://www.opensource.org/licenses/gpl-license.html
 * http://www.gnu.org/copyleft/gpl.html
 */

/*
 * A driver for the Freescale Semiconductor i.MXC CPUfreq module.
 * The CPUFREQ driver is for controlling CPU frequency. It allows you to change
 * the CPU clock speed on the fly.
 */

#include <linux/module.h>
#include <linux/cpufreq.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <mach/hardware.h>

#define CLK32_FREQ  32768
#define NANOSECOND  (1000 * 1000 * 1000)

struct cpu_op *(*get_cpu_op)(int *op);

static int cpu_freq_khz_min;
static int cpu_freq_khz_max;

static struct clk *cpu_clk;
static struct cpufreq_frequency_table *imx_freq_table;

static int cpu_op_nr;
static struct cpu_op *cpu_op_tbl;

static int set_cpu_freq(int freq)
{
    int ret = 0;
    int org_cpu_rate;

    org_cpu_rate = clk_get_rate(cpu_clk);
    if (org_cpu_rate == freq)
        return ret;

    ret = clk_set_rate(cpu_clk, freq);
    if (ret != 0) {
        printk(KERN_DEBUG "cannot set CPU clock rate\n");
        return ret;
    }

    return ret;
}

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

    return cpufreq_frequency_table_verify(policy, imx_freq_table);
}

static unsigned int mxc_get_speed(unsigned int cpu)
{
    if (cpu)
        return 0;

    return clk_get_rate(cpu_clk) / 1000;
}

static int mxc_set_target(struct cpufreq_policy *policy,
              unsigned int target_freq, unsigned int relation)
{
    struct cpufreq_freqs freqs;
    int freq_Hz;
    int ret = 0;
    unsigned int index;

    cpufreq_frequency_table_target(policy, imx_freq_table,
            target_freq, relation, &index);
    freq_Hz = imx_freq_table[index].frequency * 1000;

    freqs.old = clk_get_rate(cpu_clk) / 1000;
    freqs.new = freq_Hz / 1000;
    freqs.cpu = 0;
    freqs.flags = 0;
    cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);

    ret = set_cpu_freq(freq_Hz);

    cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

    return ret;
}

static int mxc_cpufreq_init(struct cpufreq_policy *policy)
{
    int ret;
    int i;

    printk(KERN_INFO "i.MXC CPU frequency driver\n");

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

    if (!get_cpu_op)
        return -EINVAL;

    cpu_clk = clk_get(NULL, "cpu_clk");
    if (IS_ERR(cpu_clk)) {
        printk(KERN_ERR "%s: failed to get cpu clock\n", __func__);
        return PTR_ERR(cpu_clk);
    }

    cpu_op_tbl = get_cpu_op(&cpu_op_nr);

    cpu_freq_khz_min = cpu_op_tbl[0].cpu_rate / 1000;
    cpu_freq_khz_max = cpu_op_tbl[0].cpu_rate / 1000;

    imx_freq_table = kmalloc(
        sizeof(struct cpufreq_frequency_table) * (cpu_op_nr + 1),
            GFP_KERNEL);
    if (!imx_freq_table) {
        ret = -ENOMEM;
        goto err1;
    }

    for (i = 0; i < cpu_op_nr; i++) {
        imx_freq_table[i].index = i;
        imx_freq_table[i].frequency = cpu_op_tbl[i].cpu_rate / 1000;

        if ((cpu_op_tbl[i].cpu_rate / 1000) < cpu_freq_khz_min)
            cpu_freq_khz_min = cpu_op_tbl[i].cpu_rate / 1000;

        if ((cpu_op_tbl[i].cpu_rate / 1000) > cpu_freq_khz_max)
            cpu_freq_khz_max = cpu_op_tbl[i].cpu_rate / 1000;
    }

    imx_freq_table[i].index = i;
    imx_freq_table[i].frequency = CPUFREQ_TABLE_END;

    policy->cur = clk_get_rate(cpu_clk) / 1000;
    policy->min = policy->cpuinfo.min_freq = cpu_freq_khz_min;
    policy->max = policy->cpuinfo.max_freq = cpu_freq_khz_max;

    /* Manual states, that PLL stabilizes in two CLK32 periods */
    policy->cpuinfo.transition_latency = 2 * NANOSECOND / CLK32_FREQ;

    ret = cpufreq_frequency_table_cpuinfo(policy, imx_freq_table);

    if (ret < 0) {
        printk(KERN_ERR "%s: failed to register i.MXC CPUfreq with error code %d\n",
               __func__, ret);
        goto err;
    }

    cpufreq_frequency_table_get_attr(imx_freq_table, policy->cpu);
    return 0;
err:
    kfree(imx_freq_table);
err1:
    clk_put(cpu_clk);
    return ret;
}

static int mxc_cpufreq_exit(struct cpufreq_policy *policy)
{
    cpufreq_frequency_table_put_attr(policy->cpu);

    set_cpu_freq(cpu_freq_khz_max * 1000);
    clk_put(cpu_clk);
    kfree(imx_freq_table);
    return 0;
}

static struct cpufreq_driver mxc_driver = {
    .flags = CPUFREQ_STICKY,
    .verify = mxc_verify_speed,
    .target = mxc_set_target,
    .get = mxc_get_speed,
    .init = mxc_cpufreq_init,
    .exit = mxc_cpufreq_exit,
    .name = "imx",
};

static int __devinit mxc_cpufreq_driver_init(void)
{
    return cpufreq_register_driver(&mxc_driver);
}

static void mxc_cpufreq_driver_exit(void)
{
    cpufreq_unregister_driver(&mxc_driver);
}

module_init(mxc_cpufreq_driver_init);
module_exit(mxc_cpufreq_driver_exit);

MODULE_AUTHOR("Freescale Semiconductor Inc. Yong Shen <[email protected]>");
MODULE_DESCRIPTION("CPUfreq driver for i.MX");
MODULE_LICENSE("GPL");