bmips-cpufreq.c

/*
 * CPU frequency scaling for Broadcom BMIPS SoCs
 *
 * Copyright (c) 2017 Broadcom
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation version 2.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/cpufreq.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/slab.h>

/* for mips_hpt_frequency */
#include <asm/time.h>

#define BMIPS_CPUFREQ_PREFIX	"bmips"
#define BMIPS_CPUFREQ_NAME	BMIPS_CPUFREQ_PREFIX "-cpufreq"

#define TRANSITION_LATENCY	(25 * 1000)	/* 25 us */

#define BMIPS5_CLK_DIV_SET_SHIFT	0x7
#define BMIPS5_CLK_DIV_SHIFT		0x4
#define BMIPS5_CLK_DIV_MASK		0xf

enum bmips_type {
	BMIPS5000,
	BMIPS5200,
};

struct cpufreq_compat {
	const char *compatible;
	unsigned int bmips_type;
	unsigned int clk_mult;
	unsigned int max_freqs;
};

#define BMIPS(c, t, m, f) { \
	.compatible = c, \
	.bmips_type = (t), \
	.clk_mult = (m), \
	.max_freqs = (f), \
}

static struct cpufreq_compat bmips_cpufreq_compat[] = {
	BMIPS("brcm,bmips5000", BMIPS5000, 8, 4),
	BMIPS("brcm,bmips5200", BMIPS5200, 8, 4),
	{ }
};

static struct cpufreq_compat *priv;

static int htp_freq_to_cpu_freq(unsigned int clk_mult)
{
	return mips_hpt_frequency * clk_mult / 1000;
}

static struct cpufreq_frequency_table *
bmips_cpufreq_get_freq_table(const struct cpufreq_policy *policy)
{
	struct cpufreq_frequency_table *table;
	unsigned long cpu_freq;
	int i;

	cpu_freq = htp_freq_to_cpu_freq(priv->clk_mult);

	table = kmalloc_array(priv->max_freqs + 1, sizeof(*table), GFP_KERNEL);
	if (!table)
		return ERR_PTR(-ENOMEM);

	for (i = 0; i < priv->max_freqs; i++) {
		table[i].frequency = cpu_freq / (1 << i);
		table[i].driver_data = i;
	}
	table[i].frequency = CPUFREQ_TABLE_END;

	return table;
}

static unsigned int bmips_cpufreq_get(unsigned int cpu)
{
	unsigned int div;
	uint32_t mode;

	switch (priv->bmips_type) {
	case BMIPS5200:
	case BMIPS5000:
		mode = read_c0_brcm_mode();
		div = ((mode >> BMIPS5_CLK_DIV_SHIFT) & BMIPS5_CLK_DIV_MASK);
		break;
	default:
		div = 0;
	}

	return htp_freq_to_cpu_freq(priv->clk_mult) / (1 << div);
}

static int bmips_cpufreq_target_index(struct cpufreq_policy *policy,
				      unsigned int index)
{
	unsigned int div = policy->freq_table[index].driver_data;

	switch (priv->bmips_type) {
	case BMIPS5200:
	case BMIPS5000:
		change_c0_brcm_mode(BMIPS5_CLK_DIV_MASK << BMIPS5_CLK_DIV_SHIFT,
				    (1 << BMIPS5_CLK_DIV_SET_SHIFT) |
				    (div << BMIPS5_CLK_DIV_SHIFT));
		break;
	default:
		return -ENOTSUPP;
	}

	return 0;
}

static void bmips_cpufreq_exit(struct cpufreq_policy *policy)
{
	kfree(policy->freq_table);
}

static int bmips_cpufreq_init(struct cpufreq_policy *policy)
{
	struct cpufreq_frequency_table *freq_table;

	freq_table = bmips_cpufreq_get_freq_table(policy);
	if (IS_ERR(freq_table)) {
		pr_err("%s: couldn't determine frequency table (%ld).\n",
			BMIPS_CPUFREQ_NAME, PTR_ERR(freq_table));
		return PTR_ERR(freq_table);
	}

	cpufreq_generic_init(policy, freq_table, TRANSITION_LATENCY);
	pr_info("%s: registered\n", BMIPS_CPUFREQ_NAME);

	return 0;
}

static struct cpufreq_driver bmips_cpufreq_driver = {
	.flags		= CPUFREQ_NEED_INITIAL_FREQ_CHECK,
	.verify		= cpufreq_generic_frequency_table_verify,
	.target_index	= bmips_cpufreq_target_index,
	.get		= bmips_cpufreq_get,
	.init		= bmips_cpufreq_init,
	.exit		= bmips_cpufreq_exit,
	.name		= BMIPS_CPUFREQ_PREFIX,
};

static int __init bmips_cpufreq_driver_init(void)
{
	struct cpufreq_compat *cc;
	struct device_node *np;

	for (cc = bmips_cpufreq_compat; cc->compatible; cc++) {
		np = of_find_compatible_node(NULL, "cpu", cc->compatible);
		if (np) {
			of_node_put(np);
			priv = cc;
			break;
		}
	}

	/* We hit the guard element of the array. No compatible CPU found. */
	if (!cc->compatible)
		return -ENODEV;

	return cpufreq_register_driver(&bmips_cpufreq_driver);
}
module_init(bmips_cpufreq_driver_init);

static void __exit bmips_cpufreq_driver_exit(void)
{
	cpufreq_unregister_driver(&bmips_cpufreq_driver);
}
module_exit(bmips_cpufreq_driver_exit);

MODULE_AUTHOR("Markus Mayer <[email protected]>");
MODULE_DESCRIPTION("CPUfreq driver for Broadcom BMIPS SoCs");
MODULE_LICENSE("GPL");