cbe_cpufreq.c

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/*
 * cpufreq driver for the cell processor
 *
 * (C) Copyright IBM Deutschland Entwicklung GmbH 2005-2007
 *
 * Author: Christian Krafft <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/cpufreq.h>
#include <linux/module.h>
#include <linux/of_platform.h>

#include <asm/machdep.h>
#include <asm/prom.h>
#include <asm/cell-regs.h>
#include "cbe_cpufreq.h"

static DEFINE_MUTEX(cbe_switch_mutex);


/* the CBE supports an 8 step frequency scaling */
static struct cpufreq_frequency_table cbe_freqs[] = {
    {1, 0},
    {2, 0},
    {3, 0},
    {4, 0},
    {5, 0},
    {6, 0},
    {8, 0},
    {10,    0},
    {0, CPUFREQ_TABLE_END},
};

/*
 * hardware specific functions
 */

static int set_pmode(unsigned int cpu, unsigned int slow_mode)
{
    int rc;

    if (cbe_cpufreq_has_pmi)
        rc = cbe_cpufreq_set_pmode_pmi(cpu, slow_mode);
    else
        rc = cbe_cpufreq_set_pmode(cpu, slow_mode);

    pr_debug("register contains slow mode %d\n", cbe_cpufreq_get_pmode(cpu));

    return rc;
}

/*
 * cpufreq functions
 */

static int cbe_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
    const u32 *max_freqp;
    u32 max_freq;
    int i, cur_pmode;
    struct device_node *cpu;

    cpu = of_get_cpu_node(policy->cpu, NULL);

    if (!cpu)
        return -ENODEV;

    pr_debug("init cpufreq on CPU %d\n", policy->cpu);

    /*
     * Let's check we can actually get to the CELL regs
     */
    if (!cbe_get_cpu_pmd_regs(policy->cpu) ||
        !cbe_get_cpu_mic_tm_regs(policy->cpu)) {
        pr_info("invalid CBE regs pointers for cpufreq\n");
        return -EINVAL;
    }

    max_freqp = of_get_property(cpu, "clock-frequency", NULL);

    of_node_put(cpu);

    if (!max_freqp)
        return -EINVAL;

    /* we need the freq in kHz */
    max_freq = *max_freqp / 1000;

    pr_debug("max clock-frequency is at %u kHz\n", max_freq);
    pr_debug("initializing frequency table\n");

    /* initialize frequency table */
    for (i=0; cbe_freqs[i].frequency!=CPUFREQ_TABLE_END; i++) {
        cbe_freqs[i].frequency = max_freq / cbe_freqs[i].index;
        pr_debug("%d: %d\n", i, cbe_freqs[i].frequency);
    }

    /* if DEBUG is enabled set_pmode() measures the latency
     * of a transition */
    policy->cpuinfo.transition_latency = 25000;

    cur_pmode = cbe_cpufreq_get_pmode(policy->cpu);
    pr_debug("current pmode is at %d\n",cur_pmode);

    policy->cur = cbe_freqs[cur_pmode].frequency;

#ifdef CONFIG_SMP
    cpumask_copy(policy->cpus, cpu_sibling_mask(policy->cpu));
#endif

    cpufreq_frequency_table_get_attr(cbe_freqs, policy->cpu);

    /* this ensures that policy->cpuinfo_min
     * and policy->cpuinfo_max are set correctly */
    return cpufreq_frequency_table_cpuinfo(policy, cbe_freqs);
}

static int cbe_cpufreq_cpu_exit(struct cpufreq_policy *policy)
{
    cpufreq_frequency_table_put_attr(policy->cpu);
    return 0;
}

static int cbe_cpufreq_verify(struct cpufreq_policy *policy)
{
    return cpufreq_frequency_table_verify(policy, cbe_freqs);
}

static int cbe_cpufreq_target(struct cpufreq_policy *policy,
                  unsigned int target_freq,
                  unsigned int relation)
{
    int rc;
    struct cpufreq_freqs freqs;
    unsigned int cbe_pmode_new;

    cpufreq_frequency_table_target(policy,
                       cbe_freqs,
                       target_freq,
                       relation,
                       &cbe_pmode_new);

    freqs.old = policy->cur;
    freqs.new = cbe_freqs[cbe_pmode_new].frequency;
    freqs.cpu = policy->cpu;

    mutex_lock(&cbe_switch_mutex);
    cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);

    pr_debug("setting frequency for cpu %d to %d kHz, " \
         "1/%d of max frequency\n",
         policy->cpu,
         cbe_freqs[cbe_pmode_new].frequency,
         cbe_freqs[cbe_pmode_new].index);

    rc = set_pmode(policy->cpu, cbe_pmode_new);

    cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
    mutex_unlock(&cbe_switch_mutex);

    return rc;
}

static struct cpufreq_driver cbe_cpufreq_driver = {
    .verify     = cbe_cpufreq_verify,
    .target     = cbe_cpufreq_target,
    .init       = cbe_cpufreq_cpu_init,
    .exit       = cbe_cpufreq_cpu_exit,
    .name       = "cbe-cpufreq",
    .owner      = THIS_MODULE,
    .flags      = CPUFREQ_CONST_LOOPS,
};

/*
 * module init and destoy
 */

static int __init cbe_cpufreq_init(void)
{
    if (!machine_is(cell))
        return -ENODEV;

    return cpufreq_register_driver(&cbe_cpufreq_driver);
}

static void __exit cbe_cpufreq_exit(void)
{
    cpufreq_unregister_driver(&cbe_cpufreq_driver);
}

module_init(cbe_cpufreq_init);
module_exit(cbe_cpufreq_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Christian Krafft <[email protected]>");