cpu-tegra.c

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/*
 * arch/arm/mach-tegra/cpu-tegra.c
 *
 * Copyright (C) 2010 Google, Inc.
 *
 * Author:
 *  Colin Cross <[email protected]>
 *  Based on arch/arm/plat-omap/cpu-omap.c, (C) 2005 Nokia Corporation
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/suspend.h>


#include <mach/clk.h>

/* Frequency table index must be sequential starting at 0 */
static struct cpufreq_frequency_table freq_table[] = {
    { 0, 216000 },
    { 1, 312000 },
    { 2, 456000 },
    { 3, 608000 },
    { 4, 760000 },
    { 5, 816000 },
    { 6, 912000 },
    { 7, 1000000 },
    { 8, CPUFREQ_TABLE_END },
};

#define NUM_CPUS    2

static struct clk *cpu_clk;
static struct clk *pll_x_clk;
static struct clk *pll_p_clk;
static struct clk *emc_clk;

static unsigned long target_cpu_speed[NUM_CPUS];
static DEFINE_MUTEX(tegra_cpu_lock);
static bool is_suspended;

static int tegra_verify_speed(struct cpufreq_policy *policy)
{
    return cpufreq_frequency_table_verify(policy, freq_table);
}

static unsigned int tegra_getspeed(unsigned int cpu)
{
    unsigned long rate;

    if (cpu >= NUM_CPUS)
        return 0;

    rate = clk_get_rate(cpu_clk) / 1000;
    return rate;
}

static int tegra_cpu_clk_set_rate(unsigned long rate)
{
    int ret;

    /*
     * Take an extra reference to the main pll so it doesn't turn
     * off when we move the cpu off of it
     */
    clk_prepare_enable(pll_x_clk);

    ret = clk_set_parent(cpu_clk, pll_p_clk);
    if (ret) {
        pr_err("Failed to switch cpu to clock pll_p\n");
        goto out;
    }

    if (rate == clk_get_rate(pll_p_clk))
        goto out;

    ret = clk_set_rate(pll_x_clk, rate);
    if (ret) {
        pr_err("Failed to change pll_x to %lu\n", rate);
        goto out;
    }

    ret = clk_set_parent(cpu_clk, pll_x_clk);
    if (ret) {
        pr_err("Failed to switch cpu to clock pll_x\n");
        goto out;
    }

out:
    clk_disable_unprepare(pll_x_clk);
    return ret;
}

static int tegra_update_cpu_speed(unsigned long rate)
{
    int ret = 0;
    struct cpufreq_freqs freqs;

    freqs.old = tegra_getspeed(0);
    freqs.new = rate;

    if (freqs.old == freqs.new)
        return ret;

    /*
     * Vote on memory bus frequency based on cpu frequency
     * This sets the minimum frequency, display or avp may request higher
     */
    if (rate >= 816000)
        clk_set_rate(emc_clk, 600000000); /* cpu 816 MHz, emc max */
    else if (rate >= 456000)
        clk_set_rate(emc_clk, 300000000); /* cpu 456 MHz, emc 150Mhz */
    else
        clk_set_rate(emc_clk, 100000000);  /* emc 50Mhz */

    for_each_online_cpu(freqs.cpu)
        cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);

#ifdef CONFIG_CPU_FREQ_DEBUG
    printk(KERN_DEBUG "cpufreq-tegra: transition: %u --> %u\n",
           freqs.old, freqs.new);
#endif

    ret = tegra_cpu_clk_set_rate(freqs.new * 1000);
    if (ret) {
        pr_err("cpu-tegra: Failed to set cpu frequency to %d kHz\n",
            freqs.new);
        return ret;
    }

    for_each_online_cpu(freqs.cpu)
        cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

    return 0;
}

static unsigned long tegra_cpu_highest_speed(void)
{
    unsigned long rate = 0;
    int i;

    for_each_online_cpu(i)
        rate = max(rate, target_cpu_speed[i]);
    return rate;
}

static int tegra_target(struct cpufreq_policy *policy,
               unsigned int target_freq,
               unsigned int relation)
{
    unsigned int idx;
    unsigned int freq;
    int ret = 0;

    mutex_lock(&tegra_cpu_lock);

    if (is_suspended) {
        ret = -EBUSY;
        goto out;
    }

    cpufreq_frequency_table_target(policy, freq_table, target_freq,
        relation, &idx);

    freq = freq_table[idx].frequency;

    target_cpu_speed[policy->cpu] = freq;

    ret = tegra_update_cpu_speed(tegra_cpu_highest_speed());

out:
    mutex_unlock(&tegra_cpu_lock);
    return ret;
}

static int tegra_pm_notify(struct notifier_block *nb, unsigned long event,
    void *dummy)
{
    mutex_lock(&tegra_cpu_lock);
    if (event == PM_SUSPEND_PREPARE) {
        is_suspended = true;
        pr_info("Tegra cpufreq suspend: setting frequency to %d kHz\n",
            freq_table[0].frequency);
        tegra_update_cpu_speed(freq_table[0].frequency);
    } else if (event == PM_POST_SUSPEND) {
        is_suspended = false;
    }
    mutex_unlock(&tegra_cpu_lock);

    return NOTIFY_OK;
}

static struct notifier_block tegra_cpu_pm_notifier = {
    .notifier_call = tegra_pm_notify,
};

static int tegra_cpu_init(struct cpufreq_policy *policy)
{
    if (policy->cpu >= NUM_CPUS)
        return -EINVAL;

    cpu_clk = clk_get_sys(NULL, "cpu");
    if (IS_ERR(cpu_clk))
        return PTR_ERR(cpu_clk);

    pll_x_clk = clk_get_sys(NULL, "pll_x");
    if (IS_ERR(pll_x_clk))
        return PTR_ERR(pll_x_clk);

    pll_p_clk = clk_get_sys(NULL, "pll_p");
    if (IS_ERR(pll_p_clk))
        return PTR_ERR(pll_p_clk);

    emc_clk = clk_get_sys("cpu", "emc");
    if (IS_ERR(emc_clk)) {
        clk_put(cpu_clk);
        return PTR_ERR(emc_clk);
    }

    clk_prepare_enable(emc_clk);
    clk_prepare_enable(cpu_clk);

    cpufreq_frequency_table_cpuinfo(policy, freq_table);
    cpufreq_frequency_table_get_attr(freq_table, policy->cpu);
    policy->cur = tegra_getspeed(policy->cpu);
    target_cpu_speed[policy->cpu] = policy->cur;

    /* FIXME: what's the actual transition time? */
    policy->cpuinfo.transition_latency = 300 * 1000;

    policy->shared_type = CPUFREQ_SHARED_TYPE_ALL;
    cpumask_copy(policy->related_cpus, cpu_possible_mask);

    if (policy->cpu == 0)
        register_pm_notifier(&tegra_cpu_pm_notifier);

    return 0;
}

static int tegra_cpu_exit(struct cpufreq_policy *policy)
{
    cpufreq_frequency_table_cpuinfo(policy, freq_table);
    clk_disable_unprepare(emc_clk);
    clk_put(emc_clk);
    clk_put(cpu_clk);
    return 0;
}

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

static struct cpufreq_driver tegra_cpufreq_driver = {
    .verify     = tegra_verify_speed,
    .target     = tegra_target,
    .get        = tegra_getspeed,
    .init       = tegra_cpu_init,
    .exit       = tegra_cpu_exit,
    .name       = "tegra",
    .attr       = tegra_cpufreq_attr,
};

static int __init tegra_cpufreq_init(void)
{
    return cpufreq_register_driver(&tegra_cpufreq_driver);
}

static void __exit tegra_cpufreq_exit(void)
{
        cpufreq_unregister_driver(&tegra_cpufreq_driver);
}


MODULE_AUTHOR("Colin Cross <[email protected]>");
MODULE_DESCRIPTION("cpufreq driver for Nvidia Tegra2");
MODULE_LICENSE("GPL");
module_init(tegra_cpufreq_init);
module_exit(tegra_cpufreq_exit);