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cpufreq.c

/*
 * File:     arch/blackfin/mach-common/cpufreq.c
 * Based on:
 * Author:
 *
 * Created:
 * Description:    Blackfin core clock scaling
 *
 * Modified:
 *           Copyright 2004-2008 Analog Devices Inc.
 *
 * Bugs:     Enter bugs at http://blackfin.uclinux.org/
 *
 * 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 of the License, 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, see the file COPYING, or write
 * to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA      02110-1301  USA
 */

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/fs.h>
#include <asm/blackfin.h>
#include <asm/time.h>


/* this is the table of CCLK frequencies, in Hz */
/* .index is the entry in the auxillary dpm_state_table[] */
static struct cpufreq_frequency_table bfin_freq_table[] = {
      {
            .frequency = CPUFREQ_TABLE_END,
            .index = 0,
      },
      {
            .frequency = CPUFREQ_TABLE_END,
            .index = 1,
      },
      {
            .frequency = CPUFREQ_TABLE_END,
            .index = 2,
      },
      {
            .frequency = CPUFREQ_TABLE_END,
            .index = 0,
      },
};

static struct bfin_dpm_state {
      unsigned int csel; /* system clock divider */
      unsigned int tscale; /* change the divider on the core timer interrupt */
} dpm_state_table[3];

/*
   normalized to maximum frequncy offset for CYCLES,
   used in time-ts cycles clock source, but could be used
   somewhere also.
 */
unsigned long long __bfin_cycles_off;
unsigned int __bfin_cycles_mod;

/**************************************************************************/

static unsigned int bfin_getfreq(unsigned int cpu)
{
      /* The driver only support single cpu */
      if (cpu != 0)
            return -1;

      return get_cclk();
}


static int bfin_target(struct cpufreq_policy *policy,
                  unsigned int target_freq, unsigned int relation)
{
      unsigned int index, plldiv, tscale;
      unsigned long flags, cclk_hz;
      struct cpufreq_freqs freqs;
      cycles_t cycles;

      if (cpufreq_frequency_table_target(policy, bfin_freq_table,
             target_freq, relation, &index))
            return -EINVAL;

      cclk_hz = bfin_freq_table[index].frequency;

      freqs.old = bfin_getfreq(0);
      freqs.new = cclk_hz;
      freqs.cpu = 0;

      pr_debug("cpufreq: changing cclk to %lu; target = %u, oldfreq = %u\n",
             cclk_hz, target_freq, freqs.old);

      cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
      local_irq_save(flags);
            plldiv = (bfin_read_PLL_DIV() & SSEL) | dpm_state_table[index].csel;
            tscale = dpm_state_table[index].tscale;
            bfin_write_PLL_DIV(plldiv);
            /* we have to adjust the core timer, because it is using cclk */
            bfin_write_TSCALE(tscale);
            cycles = get_cycles();
            SSYNC();
      cycles += 10; /* ~10 cycles we loose after get_cycles() */
      __bfin_cycles_off += (cycles << __bfin_cycles_mod) - (cycles << index);
      __bfin_cycles_mod = index;
      local_irq_restore(flags);
      /* TODO: just test case for cycles clock source, remove later */
      pr_debug("cpufreq: done\n");
      cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

      return 0;
}

static int bfin_verify_speed(struct cpufreq_policy *policy)
{
      return cpufreq_frequency_table_verify(policy, bfin_freq_table);
}

static int __init __bfin_cpu_init(struct cpufreq_policy *policy)
{

      unsigned long cclk, sclk, csel, min_cclk;
      int index;

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

      cclk = get_cclk();
      sclk = get_sclk();

#if ANOMALY_05000273 || (!defined(CONFIG_BF54x) && defined(CONFIG_BFIN_DCACHE))
      min_cclk = sclk * 2;
#else
      min_cclk = sclk;
#endif
      csel = ((bfin_read_PLL_DIV() & CSEL) >> 4);

      for (index = 0;  (cclk >> index) >= min_cclk && csel <= 3; index++, csel++) {
            bfin_freq_table[index].frequency = cclk >> index;
            dpm_state_table[index].csel = csel << 4; /* Shift now into PLL_DIV bitpos */
            dpm_state_table[index].tscale =  (TIME_SCALE / (1 << csel)) - 1;

            pr_debug("cpufreq: freq:%d csel:%d tscale:%d\n",
                                     bfin_freq_table[index].frequency,
                                     dpm_state_table[index].csel,
                                     dpm_state_table[index].tscale);
      }

      policy->governor = CPUFREQ_DEFAULT_GOVERNOR;

      policy->cpuinfo.transition_latency = (bfin_read_PLL_LOCKCNT() / (sclk / 1000000)) * 1000;
      /*Now ,only support one cpu */
      policy->cur = cclk;
      cpufreq_frequency_table_get_attr(bfin_freq_table, policy->cpu);
      return cpufreq_frequency_table_cpuinfo(policy, bfin_freq_table);
}

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

static struct cpufreq_driver bfin_driver = {
      .verify = bfin_verify_speed,
      .target = bfin_target,
      .get = bfin_getfreq,
      .init = __bfin_cpu_init,
      .name = "bfin cpufreq",
      .owner = THIS_MODULE,
      .attr = bfin_freq_attr,
};

static int __init bfin_cpu_init(void)
{
      return cpufreq_register_driver(&bfin_driver);
}

static void __exit bfin_cpu_exit(void)
{
      cpufreq_unregister_driver(&bfin_driver);
}

MODULE_AUTHOR("Michael Hennerich <hennerich@blackfin.uclinux.org>");
MODULE_DESCRIPTION("cpufreq driver for Blackfin");
MODULE_LICENSE("GPL");

module_init(bfin_cpu_init);
module_exit(bfin_cpu_exit);

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