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cbe_cpufreq.c

/*
 * cpufreq driver for the cell processor
 *
 * (C) Copyright IBM Deutschland Entwicklung GmbH 2005-2007
 *
 * Author: Christian Krafft <krafft@de.ibm.com>
 *
 * 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 <asm/machdep.h>
#include <asm/of_platform.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
      policy->cpus = per_cpu(cpu_sibling_map, 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 <krafft@de.ibm.com>");

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