linux/drivers/macintosh/windfarm_cpufreq_clamp.c

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <linux/cpufreq.h>

#include <asm/prom.h>

#include "windfarm.h"

#define VERSION "0.3"

static int clamped;
static struct wf_control *clamp_control;

static int clamp_notifier_call(struct notifier_block *self,
			       unsigned long event, void *data)
{
	struct cpufreq_policy *p = data;
	unsigned long max_freq;

	if (event != CPUFREQ_ADJUST)
		return 0;

	max_freq = clamped ? (p->cpuinfo.min_freq) : (p->cpuinfo.max_freq);
	cpufreq_verify_within_limits(p, 0, max_freq);

	return 0;
}

static struct notifier_block clamp_notifier = {
	.notifier_call = clamp_notifier_call,
};

static int clamp_set(struct wf_control *ct, s32 value)
{
	if (value)
		printk(KERN_INFO "windfarm: Clamping CPU frequency to "
		       "minimum !\n");
	else
		printk(KERN_INFO "windfarm: CPU frequency unclamped !\n");
	clamped = value;
	cpufreq_update_policy(0);
	return 0;
}

static int clamp_get(struct wf_control *ct, s32 *value)
{
	*value = clamped;
	return 0;
}

static s32 clamp_min(struct wf_control *ct)
{
	return 0;
}

static s32 clamp_max(struct wf_control *ct)
{
	return 1;
}

static const struct wf_control_ops clamp_ops = {
	.set_value	= clamp_set,
	.get_value	= clamp_get,
	.get_min	= clamp_min,
	.get_max	= clamp_max,
	.owner		= THIS_MODULE,
};

static int __init wf_cpufreq_clamp_init(void)
{
	struct wf_control *clamp;

	clamp = kmalloc(sizeof(struct wf_control), GFP_KERNEL);
	if (clamp == NULL)
		return -ENOMEM;
	cpufreq_register_notifier(&clamp_notifier, CPUFREQ_POLICY_NOTIFIER);
	clamp->ops = &clamp_ops;
	clamp->name = "cpufreq-clamp";
	if (wf_register_control(clamp))
		goto fail;
	clamp_control = clamp;
	return 0;
 fail:
	kfree(clamp);
	return -ENODEV;
}

static void __exit wf_cpufreq_clamp_exit(void)
{
	if (clamp_control)
		wf_unregister_control(clamp_control);
}


module_init(wf_cpufreq_clamp_init);
module_exit(wf_cpufreq_clamp_exit);

MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
MODULE_DESCRIPTION("CPU frequency clamp for PowerMacs thermal control");
MODULE_LICENSE("GPL");