kernel/drivers/cpufreq/unicore2-cpufreq.c

   1 /*
   2  * clock scaling for the UniCore-II
   3  *
   4  * Code specific to PKUnity SoC and UniCore ISA
   5  *
   6  *      Maintained by GUAN Xue-tao <gxt@mprc.pku.edu.cn>
   7  *      Copyright (C) 2001-2010 Guan Xuetao
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13
  14 #include <linux/err.h>
  15 #include <linux/kernel.h>
  16 #include <linux/types.h>
  17 #include <linux/init.h>
  18 #include <linux/clk.h>
  19 #include <linux/cpufreq.h>
  20
  21 #include <mach/hardware.h>
  22
  23 static struct cpufreq_driver ucv2_driver;
  24
  25 /* make sure that only the "userspace" governor is run
  26  * -- anything else wouldn't make sense on this platform, anyway.
  27  */
  28 static int ucv2_verify_speed(struct cpufreq_policy *policy)
  29 {
  30         if (policy->cpu)
  31                 return -EINVAL;
  32
  33         cpufreq_verify_within_cpu_limits(policy);
  34         return 0;
  35 }
  36
  37 static int ucv2_target(struct cpufreq_policy *policy,
  38                          unsigned int target_freq,
  39                          unsigned int relation)
  40 {
  41         struct cpufreq_freqs freqs;
  42         int ret;
  43
  44         freqs.old = policy->cur;
  45         freqs.new = target_freq;
  46
  47         cpufreq_freq_transition_begin(policy, &freqs);
  48         ret = clk_set_rate(policy->clk, target_freq * 1000);
  49         cpufreq_freq_transition_end(policy, &freqs, ret);
  50
  51         return ret;
  52 }
  53
  54 static int __init ucv2_cpu_init(struct cpufreq_policy *policy)
  55 {
  56         if (policy->cpu != 0)
  57                 return -EINVAL;
  58
  59         policy->min = policy->cpuinfo.min_freq = 250000;
  60         policy->max = policy->cpuinfo.max_freq = 1000000;
  61         policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
  62         policy->clk = clk_get(NULL, "MAIN_CLK");
  63         return PTR_ERR_OR_ZERO(policy->clk);
  64 }
  65
  66 static struct cpufreq_driver ucv2_driver = {
  67         .flags          = CPUFREQ_STICKY,
  68         .verify         = ucv2_verify_speed,
  69         .target         = ucv2_target,
  70         .get            = cpufreq_generic_get,
  71         .init           = ucv2_cpu_init,
  72         .name           = "UniCore-II",
  73 };
  74
  75 static int __init ucv2_cpufreq_init(void)
  76 {
  77         return cpufreq_register_driver(&ucv2_driver);
  78 }
  79
  80 arch_initcall(ucv2_cpufreq_init);