1/*
  2 *  CPU frequency scaling for OMAP using OPP information
  3 *
  4 *  Copyright (C) 2005 Nokia Corporation
  5 *  Written by Tony Lindgren <tony@atomide.com>
  6 *
  7 *  Based on cpu-sa1110.c, Copyright (C) 2001 Russell King
  8 *
  9 * Copyright (C) 2007-2011 Texas Instruments, Inc.
 10 * - OMAP3/4 support by Rajendra Nayak, Santosh Shilimkar
 11 *
 12 * This program is free software; you can redistribute it and/or modify
 13 * it under the terms of the GNU General Public License version 2 as
 14 * published by the Free Software Foundation.
 15 */
 16
 17#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 18
 19#include <linux/types.h>
 20#include <linux/kernel.h>
 21#include <linux/sched.h>
 22#include <linux/cpufreq.h>
 23#include <linux/delay.h>
 24#include <linux/init.h>
 25#include <linux/err.h>
 26#include <linux/clk.h>
 27#include <linux/io.h>
 28#include <linux/pm_opp.h>
 29#include <linux/cpu.h>
 30#include <linux/module.h>
 31#include <linux/platform_device.h>
 32#include <linux/regulator/consumer.h>
 33
 34#include <asm/smp_plat.h>
 35#include <asm/cpu.h>
 36
 37/* OPP tolerance in percentage */
 38#define	OPP_TOLERANCE	4
 39
 40static struct cpufreq_frequency_table *freq_table;
 41static atomic_t freq_table_users = ATOMIC_INIT(0);
 42static struct device *mpu_dev;
 43static struct regulator *mpu_reg;
 44
 45static int omap_target(struct cpufreq_policy *policy, unsigned int index)
 46{
 47	int r, ret;
 48	struct dev_pm_opp *opp;
 49	unsigned long freq, volt = 0, volt_old = 0, tol = 0;
 50	unsigned int old_freq, new_freq;
 51
 52	old_freq = policy->cur;
 53	new_freq = freq_table[index].frequency;
 54
 55	freq = new_freq * 1000;
 56	ret = clk_round_rate(policy->clk, freq);
 57	if (ret < 0) {
 58		dev_warn(mpu_dev,
 59			 "CPUfreq: Cannot find matching frequency for %lu\n",
 60			 freq);
 61		return ret;
 62	}
 63	freq = ret;
 64
 65	if (mpu_reg) {
 66		rcu_read_lock();
 67		opp = dev_pm_opp_find_freq_ceil(mpu_dev, &freq);
 68		if (IS_ERR(opp)) {
 69			rcu_read_unlock();
 70			dev_err(mpu_dev, "%s: unable to find MPU OPP for %d\n",
 71				__func__, new_freq);
 72			return -EINVAL;
 73		}
 74		volt = dev_pm_opp_get_voltage(opp);
 75		rcu_read_unlock();
 76		tol = volt * OPP_TOLERANCE / 100;
 77		volt_old = regulator_get_voltage(mpu_reg);
 78	}
 79
 80	dev_dbg(mpu_dev, "cpufreq-omap: %u MHz, %ld mV --> %u MHz, %ld mV\n", 
 81		old_freq / 1000, volt_old ? volt_old / 1000 : -1,
 82		new_freq / 1000, volt ? volt / 1000 : -1);
 83
 84	/* scaling up?  scale voltage before frequency */
 85	if (mpu_reg && (new_freq > old_freq)) {
 86		r = regulator_set_voltage(mpu_reg, volt - tol, volt + tol);
 87		if (r < 0) {
 88			dev_warn(mpu_dev, "%s: unable to scale voltage up.\n",
 89				 __func__);
 90			return r;
 91		}
 92	}
 93
 94	ret = clk_set_rate(policy->clk, new_freq * 1000);
 95
 96	/* scaling down?  scale voltage after frequency */
 97	if (mpu_reg && (new_freq < old_freq)) {
 98		r = regulator_set_voltage(mpu_reg, volt - tol, volt + tol);
 99		if (r < 0) {
100			dev_warn(mpu_dev, "%s: unable to scale voltage down.\n",
101				 __func__);
102			clk_set_rate(policy->clk, old_freq * 1000);
103			return r;
104		}
105	}
106
107	return ret;
108}
109
110static inline void freq_table_free(void)
111{
112	if (atomic_dec_and_test(&freq_table_users))
113		dev_pm_opp_free_cpufreq_table(mpu_dev, &freq_table);
114}
115
116static int omap_cpu_init(struct cpufreq_policy *policy)
117{
118	int result;
119
120	policy->clk = clk_get(NULL, "cpufreq_ck");
121	if (IS_ERR(policy->clk))
122		return PTR_ERR(policy->clk);
123
124	if (!freq_table) {
125		result = dev_pm_opp_init_cpufreq_table(mpu_dev, &freq_table);
126		if (result) {
127			dev_err(mpu_dev,
128				"%s: cpu%d: failed creating freq table[%d]\n",
129				__func__, policy->cpu, result);
130			goto fail;
131		}
132	}
133
134	atomic_inc_return(&freq_table_users);
135
136	/* FIXME: what's the actual transition time? */
137	result = cpufreq_generic_init(policy, freq_table, 300 * 1000);
138	if (!result)
139		return 0;
140
141	freq_table_free();
142fail:
143	clk_put(policy->clk);
144	return result;
145}
146
147static int omap_cpu_exit(struct cpufreq_policy *policy)
148{
149	freq_table_free();
150	clk_put(policy->clk);
151	return 0;
152}
153
154static struct cpufreq_driver omap_driver = {
155	.flags		= CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK,
156	.verify		= cpufreq_generic_frequency_table_verify,
157	.target_index	= omap_target,
158	.get		= cpufreq_generic_get,
159	.init		= omap_cpu_init,
160	.exit		= omap_cpu_exit,
161	.name		= "omap",
162	.attr		= cpufreq_generic_attr,
163};
164
165static int omap_cpufreq_probe(struct platform_device *pdev)
166{
167	mpu_dev = get_cpu_device(0);
168	if (!mpu_dev) {
169		pr_warn("%s: unable to get the MPU device\n", __func__);
170		return -EINVAL;
171	}
172
173	mpu_reg = regulator_get(mpu_dev, "vcc");
174	if (IS_ERR(mpu_reg)) {
175		pr_warn("%s: unable to get MPU regulator\n", __func__);
176		mpu_reg = NULL;
177	} else {
178		/* 
179		 * Ensure physical regulator is present.
180		 * (e.g. could be dummy regulator.)
181		 */
182		if (regulator_get_voltage(mpu_reg) < 0) {
183			pr_warn("%s: physical regulator not present for MPU\n",
184				__func__);
185			regulator_put(mpu_reg);
186			mpu_reg = NULL;
187		}
188	}
189
190	return cpufreq_register_driver(&omap_driver);
191}
192
193static int omap_cpufreq_remove(struct platform_device *pdev)
194{
195	return cpufreq_unregister_driver(&omap_driver);
196}
197
198static struct platform_driver omap_cpufreq_platdrv = {
199	.driver = {
200		.name	= "omap-cpufreq",
201	},
202	.probe		= omap_cpufreq_probe,
203	.remove		= omap_cpufreq_remove,
204};
205module_platform_driver(omap_cpufreq_platdrv);
206
207MODULE_DESCRIPTION("cpufreq driver for OMAP SoCs");
208MODULE_LICENSE("GPL");