cpufreq.c

/*
 * Copyright (C) 2010 Freescale Semiconductor, Inc. All Rights Reserved.
 */

/*
 * The code contained herein is licensed under the GNU General Public
 * License. You may obtain a copy of the GNU General Public License
 * Version 2 or later at the following locations:
 *
 * http://www.opensource.org/licenses/gpl-license.html
 * http://www.gnu.org/copyleft/gpl.html
 */

/*
 * A driver for the Freescale Semiconductor i.MXC CPUfreq module.
 * The CPUFREQ driver is for controling CPU frequency. It allows you to change
 * the CPU clock speed on the fly.
 */

#include <linux/cpufreq.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <mach/hardware.h>
#include <mach/clock.h>

#define CLK32_FREQ	32768
#define NANOSECOND	(1000 * 1000 * 1000)

struct cpu_op *(*get_cpu_op)(int *op);

static int cpu_freq_khz_min;
static int cpu_freq_khz_max;

static struct clk *cpu_clk;
static struct cpufreq_frequency_table *imx_freq_table;

static int cpu_op_nr;
static struct cpu_op *cpu_op_tbl;

static int set_cpu_freq(int freq)
{
	int ret = 0;
	int org_cpu_rate;

	org_cpu_rate = clk_get_rate(cpu_clk);
	if (org_cpu_rate == freq)
		return ret;

	ret = clk_set_rate(cpu_clk, freq);
	if (ret != 0) {
		printk(KERN_DEBUG "cannot set CPU clock rate\n");
		return ret;
	}

	return ret;
}

static int mxc_verify_speed(struct cpufreq_policy *policy)
{
	if (policy->cpu != 0)
		return -EINVAL;

	return cpufreq_frequency_table_verify(policy, imx_freq_table);
}

static unsigned int mxc_get_speed(unsigned int cpu)
{
	if (cpu)
		return 0;

	return clk_get_rate(cpu_clk) / 1000;
}

static int mxc_set_target(struct cpufreq_policy *policy,
			  unsigned int target_freq, unsigned int relation)
{
	struct cpufreq_freqs freqs;
	int freq_Hz;
	int ret = 0;
	unsigned int index;

	cpufreq_frequency_table_target(policy, imx_freq_table,
			target_freq, relation, &index);
	freq_Hz = imx_freq_table[index].frequency * 1000;

	freqs.old = clk_get_rate(cpu_clk) / 1000;
	freqs.new = freq_Hz / 1000;
	freqs.cpu = 0;
	freqs.flags = 0;
	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);

	ret = set_cpu_freq(freq_Hz);

	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

	return ret;
}

static int __init mxc_cpufreq_init(struct cpufreq_policy *policy)
{
	int ret;
	int i;

	printk(KERN_INFO "i.MXC CPU frequency driver\n");

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

	if (!get_cpu_op)
		return -EINVAL;

	cpu_clk = clk_get(NULL, "cpu_clk");
	if (IS_ERR(cpu_clk)) {
		printk(KERN_ERR "%s: failed to get cpu clock\n", __func__);
		return PTR_ERR(cpu_clk);
	}

	cpu_op_tbl = get_cpu_op(&cpu_op_nr);

	cpu_freq_khz_min = cpu_op_tbl[0].cpu_rate / 1000;
	cpu_freq_khz_max = cpu_op_tbl[0].cpu_rate / 1000;

	imx_freq_table = kmalloc(
		sizeof(struct cpufreq_frequency_table) * (cpu_op_nr + 1),
			GFP_KERNEL);
	if (!imx_freq_table) {
		ret = -ENOMEM;
		goto err1;
	}

	for (i = 0; i < cpu_op_nr; i++) {
		imx_freq_table[i].index = i;
		imx_freq_table[i].frequency = cpu_op_tbl[i].cpu_rate / 1000;

		if ((cpu_op_tbl[i].cpu_rate / 1000) < cpu_freq_khz_min)
			cpu_freq_khz_min = cpu_op_tbl[i].cpu_rate / 1000;

		if ((cpu_op_tbl[i].cpu_rate / 1000) > cpu_freq_khz_max)
			cpu_freq_khz_max = cpu_op_tbl[i].cpu_rate / 1000;
	}

	imx_freq_table[i].index = i;
	imx_freq_table[i].frequency = CPUFREQ_TABLE_END;

	policy->cur = clk_get_rate(cpu_clk) / 1000;
	policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
	policy->min = policy->cpuinfo.min_freq = cpu_freq_khz_min;
	policy->max = policy->cpuinfo.max_freq = cpu_freq_khz_max;

	/* Manual states, that PLL stabilizes in two CLK32 periods */
	policy->cpuinfo.transition_latency = 2 * NANOSECOND / CLK32_FREQ;

	ret = cpufreq_frequency_table_cpuinfo(policy, imx_freq_table);

	if (ret < 0) {
		printk(KERN_ERR "%s: failed to register i.MXC CPUfreq \
				with error code %d\n", __func__, ret);
		goto err;
	}

	cpufreq_frequency_table_get_attr(imx_freq_table, policy->cpu);
	return 0;
err:
	kfree(imx_freq_table);
err1:
	clk_put(cpu_clk);
	return ret;
}

static int mxc_cpufreq_exit(struct cpufreq_policy *policy)
{
	cpufreq_frequency_table_put_attr(policy->cpu);

	set_cpu_freq(cpu_freq_khz_max * 1000);
	clk_put(cpu_clk);
	kfree(imx_freq_table);
	return 0;
}

static struct cpufreq_driver mxc_driver = {
	.flags = CPUFREQ_STICKY,
	.verify = mxc_verify_speed,
	.target = mxc_set_target,
	.get = mxc_get_speed,
	.init = mxc_cpufreq_init,
	.exit = mxc_cpufreq_exit,
	.name = "imx",
};

static int __devinit mxc_cpufreq_driver_init(void)
{
	return cpufreq_register_driver(&mxc_driver);
}

static void mxc_cpufreq_driver_exit(void)
{
	cpufreq_unregister_driver(&mxc_driver);
}

module_init(mxc_cpufreq_driver_init);
module_exit(mxc_cpufreq_driver_exit);

MODULE_AUTHOR("Freescale Semiconductor Inc. Yong Shen <yong.shen@linaro.org>");
MODULE_DESCRIPTION("CPUfreq driver for i.MX");
MODULE_LICENSE("GPL");