drivers/macintosh/windfarm_cpufreq_clamp.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/types.h>
   3 #include <linux/errno.h>
   4 #include <linux/kernel.h>
   5 #include <linux/delay.h>
   6 #include <linux/slab.h>
   7 #include <linux/init.h>
   8 #include <linux/wait.h>
   9 #include <linux/cpufreq.h>
  10
  11 #include <asm/prom.h>
  12
  13 #include "windfarm.h"
  14
  15 #define VERSION "0.3"
  16
  17 static int clamped;
  18 static struct wf_control *clamp_control;
  19
  20 static int clamp_notifier_call(struct notifier_block *self,
  21                                unsigned long event, void *data)
  22 {
  23         struct cpufreq_policy *p = data;
  24         unsigned long max_freq;
  25
  26         if (event != CPUFREQ_ADJUST)
  27                 return 0;
  28
  29         max_freq = clamped ? (p->cpuinfo.min_freq) : (p->cpuinfo.max_freq);
  30         cpufreq_verify_within_limits(p, 0, max_freq);
  31
  32         return 0;
  33 }
  34
  35 static struct notifier_block clamp_notifier = {
  36         .notifier_call = clamp_notifier_call,
  37 };
  38
  39 static int clamp_set(struct wf_control *ct, s32 value)
  40 {
  41         if (value)
  42                 printk(KERN_INFO "windfarm: Clamping CPU frequency to "
  43                        "minimum !\n");
  44         else
  45                 printk(KERN_INFO "windfarm: CPU frequency unclamped !\n");
  46         clamped = value;
  47         cpufreq_update_policy(0);
  48         return 0;
  49 }
  50
  51 static int clamp_get(struct wf_control *ct, s32 *value)
  52 {
  53         *value = clamped;
  54         return 0;
  55 }
  56
  57 static s32 clamp_min(struct wf_control *ct)
  58 {
  59         return 0;
  60 }
  61
  62 static s32 clamp_max(struct wf_control *ct)
  63 {
  64         return 1;
  65 }
  66
  67 static const struct wf_control_ops clamp_ops = {
  68         .set_value      = clamp_set,
  69         .get_value      = clamp_get,
  70         .get_min        = clamp_min,
  71         .get_max        = clamp_max,
  72         .owner          = THIS_MODULE,
  73 };
  74
  75 static int __init wf_cpufreq_clamp_init(void)
  76 {
  77         struct wf_control *clamp;
  78
  79         clamp = kmalloc(sizeof(struct wf_control), GFP_KERNEL);
  80         if (clamp == NULL)
  81                 return -ENOMEM;
  82         cpufreq_register_notifier(&clamp_notifier, CPUFREQ_POLICY_NOTIFIER);
  83         clamp->ops = &clamp_ops;
  84         clamp->name = "cpufreq-clamp";
  85         if (wf_register_control(clamp))
  86                 goto fail;
  87         clamp_control = clamp;
  88         return 0;
  89  fail:
  90         kfree(clamp);
  91         return -ENODEV;
  92 }
  93
  94 static void __exit wf_cpufreq_clamp_exit(void)
  95 {
  96         if (clamp_control)
  97                 wf_unregister_control(clamp_control);
  98 }
  99
 100
 101 module_init(wf_cpufreq_clamp_init);
 102 module_exit(wf_cpufreq_clamp_exit);
 103
 104 MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
 105 MODULE_DESCRIPTION("CPU frequency clamp for PowerMacs thermal control");
 106 MODULE_LICENSE("GPL");
 107