arch/unicore32/kernel/cpu-ucv2.c

   1 /*
   2  * linux/arch/unicore32/kernel/cpu-ucv2.c: 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/kernel.h>
  15 #include <linux/types.h>
  16 #include <linux/init.h>
  17 #include <linux/clk.h>
  18 #include <linux/cpufreq.h>
  19
  20 #include <mach/hardware.h>
  21
  22 static struct cpufreq_driver ucv2_driver;
  23
  24 /* make sure that only the "userspace" governor is run
  25  * -- anything else wouldn't make sense on this platform, anyway.
  26  */
  27 int ucv2_verify_speed(struct cpufreq_policy *policy)
  28 {
  29         if (policy->cpu)
  30                 return -EINVAL;
  31
  32         cpufreq_verify_within_limits(policy,
  33                         policy->cpuinfo.min_freq, policy->cpuinfo.max_freq);
  34
  35         return 0;
  36 }
  37
  38 static unsigned int ucv2_getspeed(unsigned int cpu)
  39 {
  40         struct clk *mclk = clk_get(NULL, "MAIN_CLK");
  41
  42         if (cpu)
  43                 return 0;
  44         return clk_get_rate(mclk)/1000;
  45 }
  46
  47 static int ucv2_target(struct cpufreq_policy *policy,
  48                          unsigned int target_freq,
  49                          unsigned int relation)
  50 {
  51         unsigned int cur = ucv2_getspeed(0);
  52         struct cpufreq_freqs freqs;
  53         struct clk *mclk = clk_get(NULL, "MAIN_CLK");
  54
  55         cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
  56
  57         if (!clk_set_rate(mclk, target_freq * 1000)) {
  58                 freqs.old = cur;
  59                 freqs.new = target_freq;
  60                 freqs.cpu = 0;
  61         }
  62
  63         cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
  64
  65         return 0;
  66 }
  67
  68 static int __init ucv2_cpu_init(struct cpufreq_policy *policy)
  69 {
  70         if (policy->cpu != 0)
  71                 return -EINVAL;
  72         policy->cur = ucv2_getspeed(0);
  73         policy->min = policy->cpuinfo.min_freq = 250000;
  74         policy->max = policy->cpuinfo.max_freq = 1000000;
  75         policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
  76         return 0;
  77 }
  78
  79 static struct cpufreq_driver ucv2_driver = {
  80         .flags          = CPUFREQ_STICKY,
  81         .verify         = ucv2_verify_speed,
  82         .target         = ucv2_target,
  83         .get            = ucv2_getspeed,
  84         .init           = ucv2_cpu_init,
  85         .name           = "UniCore-II",
  86 };
  87
  88 static int __init ucv2_cpufreq_init(void)
  89 {
  90         return cpufreq_register_driver(&ucv2_driver);
  91 }
  92
  93 arch_initcall(ucv2_cpufreq_init);