spear-cpufreq.c

/*
 * drivers/cpufreq/spear-cpufreq.c
 *
 * CPU Frequency Scaling for SPEAr platform
 *
 * Copyright (C) 2012 ST Microelectronics
 * Deepak Sikri <deepak.sikri@st.com>
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/slab.h>
#include <linux/types.h>

/* SPEAr CPUFreq driver data structure */
static struct {
	struct clk *clk;
	unsigned int transition_latency;
	struct cpufreq_frequency_table *freq_tbl;
	u32 cnt;
} spear_cpufreq;

static unsigned int spear_cpufreq_get(unsigned int cpu)
{
	return clk_get_rate(spear_cpufreq.clk) / 1000;
}

static struct clk *spear1340_cpu_get_possible_parent(unsigned long newfreq)
{
	struct clk *sys_pclk;
	int pclk;
	/*
	 * In SPEAr1340, cpu clk's parent sys clk can take input from
	 * following sources
	 */
	const char *sys_clk_src[] = {
		"sys_syn_clk",
		"pll1_clk",
		"pll2_clk",
		"pll3_clk",
	};

	/*
	 * As sys clk can have multiple source with their own range
	 * limitation so we choose possible sources accordingly
	 */
	if (newfreq <= 300000000)
		pclk = 0; /* src is sys_syn_clk */
	else if (newfreq > 300000000 && newfreq <= 500000000)
		pclk = 3; /* src is pll3_clk */
	else if (newfreq == 600000000)
		pclk = 1; /* src is pll1_clk */
	else
		return ERR_PTR(-EINVAL);

	/* Get parent to sys clock */
	sys_pclk = clk_get(NULL, sys_clk_src[pclk]);
	if (IS_ERR(sys_pclk))
		pr_err("Failed to get %s clock\n", sys_clk_src[pclk]);

	return sys_pclk;
}

/*
 * In SPEAr1340, we cannot use newfreq directly because we need to actually
 * access a source clock (clk) which might not be ancestor of cpu at present.
 * Hence in SPEAr1340 we would operate on source clock directly before switching
 * cpu clock to it.
 */
static int spear1340_set_cpu_rate(struct clk *sys_pclk, unsigned long newfreq)
{
	struct clk *sys_clk;
	int ret = 0;

	sys_clk = clk_get_parent(spear_cpufreq.clk);
	if (IS_ERR(sys_clk)) {
		pr_err("failed to get cpu's parent (sys) clock\n");
		return PTR_ERR(sys_clk);
	}

	/* Set the rate of the source clock before changing the parent */
	ret = clk_set_rate(sys_pclk, newfreq);
	if (ret) {
		pr_err("Failed to set sys clk rate to %lu\n", newfreq);
		return ret;
	}

	ret = clk_set_parent(sys_clk, sys_pclk);
	if (ret) {
		pr_err("Failed to set sys clk parent\n");
		return ret;
	}

	return 0;
}

static int spear_cpufreq_target(struct cpufreq_policy *policy,
		unsigned int index)
{
	struct cpufreq_freqs freqs;
	long newfreq;
	struct clk *srcclk;
	int ret, mult = 1;

	freqs.old = spear_cpufreq_get(0);
	newfreq = spear_cpufreq.freq_tbl[index].frequency * 1000;

	if (of_machine_is_compatible("st,spear1340")) {
		/*
		 * SPEAr1340 is special in the sense that due to the possibility
		 * of multiple clock sources for cpu clk's parent we can have
		 * different clock source for different frequency of cpu clk.
		 * Hence we need to choose one from amongst these possible clock
		 * sources.
		 */
		srcclk = spear1340_cpu_get_possible_parent(newfreq);
		if (IS_ERR(srcclk)) {
			pr_err("Failed to get src clk\n");
			return PTR_ERR(srcclk);
		}

		/* SPEAr1340: src clk is always 2 * intended cpu clk */
		mult = 2;
	} else {
		/*
		 * src clock to be altered is ancestor of cpu clock. Hence we
		 * can directly work on cpu clk
		 */
		srcclk = spear_cpufreq.clk;
	}

	newfreq = clk_round_rate(srcclk, newfreq * mult);
	if (newfreq < 0) {
		pr_err("clk_round_rate failed for cpu src clock\n");
		return newfreq;
	}

	freqs.new = newfreq / 1000;
	freqs.new /= mult;

	cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);

	if (mult == 2)
		ret = spear1340_set_cpu_rate(srcclk, newfreq);
	else
		ret = clk_set_rate(spear_cpufreq.clk, newfreq);

	/* Get current rate after clk_set_rate, in case of failure */
	if (ret) {
		pr_err("CPU Freq: cpu clk_set_rate failed: %d\n", ret);
		freqs.new = clk_get_rate(spear_cpufreq.clk) / 1000;
	}

	cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
	return ret;
}

static int spear_cpufreq_init(struct cpufreq_policy *policy)
{
	return cpufreq_generic_init(policy, spear_cpufreq.freq_tbl,
			spear_cpufreq.transition_latency);
}

static struct cpufreq_driver spear_cpufreq_driver = {
	.name		= "cpufreq-spear",
	.flags		= CPUFREQ_STICKY,
	.verify		= cpufreq_generic_frequency_table_verify,
	.target_index	= spear_cpufreq_target,
	.get		= spear_cpufreq_get,
	.init		= spear_cpufreq_init,
	.exit		= cpufreq_generic_exit,
	.attr		= cpufreq_generic_attr,
};

static int spear_cpufreq_driver_init(void)
{
	struct device_node *np;
	const struct property *prop;
	struct cpufreq_frequency_table *freq_tbl;
	const __be32 *val;
	int cnt, i, ret;

	np = of_cpu_device_node_get(0);
	if (!np) {
		pr_err("No cpu node found");
		return -ENODEV;
	}

	if (of_property_read_u32(np, "clock-latency",
				&spear_cpufreq.transition_latency))
		spear_cpufreq.transition_latency = CPUFREQ_ETERNAL;

	prop = of_find_property(np, "cpufreq_tbl", NULL);
	if (!prop || !prop->value) {
		pr_err("Invalid cpufreq_tbl");
		ret = -ENODEV;
		goto out_put_node;
	}

	cnt = prop->length / sizeof(u32);
	val = prop->value;

	freq_tbl = kmalloc(sizeof(*freq_tbl) * (cnt + 1), GFP_KERNEL);
	if (!freq_tbl) {
		ret = -ENOMEM;
		goto out_put_node;
	}

	for (i = 0; i < cnt; i++) {
		freq_tbl[i].driver_data = i;
		freq_tbl[i].frequency = be32_to_cpup(val++);
	}

	freq_tbl[i].driver_data = i;
	freq_tbl[i].frequency = CPUFREQ_TABLE_END;

	spear_cpufreq.freq_tbl = freq_tbl;

	of_node_put(np);

	spear_cpufreq.clk = clk_get(NULL, "cpu_clk");
	if (IS_ERR(spear_cpufreq.clk)) {
		pr_err("Unable to get CPU clock\n");
		ret = PTR_ERR(spear_cpufreq.clk);
		goto out_put_mem;
	}

	ret = cpufreq_register_driver(&spear_cpufreq_driver);
	if (!ret)
		return 0;

	pr_err("failed register driver: %d\n", ret);
	clk_put(spear_cpufreq.clk);

out_put_mem:
	kfree(freq_tbl);
	return ret;

out_put_node:
	of_node_put(np);
	return ret;
}
late_initcall(spear_cpufreq_driver_init);

MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
MODULE_DESCRIPTION("SPEAr CPUFreq driver");
MODULE_LICENSE("GPL");