1/*
  2 * System Control and Power Interface (SCPI) based CPUFreq Interface driver
  3 *
  4 * Copyright (C) 2015 ARM Ltd.
  5 * Sudeep Holla <sudeep.holla@arm.com>
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License version 2 as
  9 * published by the Free Software Foundation.
 10 *
 11 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 12 * kind, whether express or implied; without even the implied warranty
 13 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 14 * GNU General Public License for more details.
 15 */
 16
 17#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 18
 19#include <linux/clk.h>
 20#include <linux/cpu.h>
 21#include <linux/cpufreq.h>
 22#include <linux/cpumask.h>
 23#include <linux/export.h>
 24#include <linux/module.h>
 25#include <linux/of_platform.h>
 26#include <linux/pm_opp.h>
 27#include <linux/scpi_protocol.h>
 28#include <linux/slab.h>
 29#include <linux/types.h>
 30
 31struct scpi_data {
 32	struct clk *clk;
 33	struct device *cpu_dev;
 34};
 35
 36static struct scpi_ops *scpi_ops;
 37
 38static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
 39{
 40	struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
 41	struct scpi_data *priv = policy->driver_data;
 42	unsigned long rate = clk_get_rate(priv->clk);
 43
 44	return rate / 1000;
 45}
 46
 47static int
 48scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
 49{
 50	unsigned long freq = policy->freq_table[index].frequency;
 51	struct scpi_data *priv = policy->driver_data;
 52	u64 rate = freq * 1000;
 53	int ret;
 54
 55	ret = clk_set_rate(priv->clk, rate);
 56
 57	if (ret)
 58		return ret;
 59
 60	if (clk_get_rate(priv->clk) != rate)
 61		return -EIO;
 62
 63	arch_set_freq_scale(policy->related_cpus, freq,
 64			    policy->cpuinfo.max_freq);
 65
 66	return 0;
 67}
 68
 69static int
 70scpi_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
 71{
 72	int cpu, domain, tdomain;
 73	struct device *tcpu_dev;
 74
 75	domain = scpi_ops->device_domain_id(cpu_dev);
 76	if (domain < 0)
 77		return domain;
 78
 79	for_each_possible_cpu(cpu) {
 80		if (cpu == cpu_dev->id)
 81			continue;
 82
 83		tcpu_dev = get_cpu_device(cpu);
 84		if (!tcpu_dev)
 85			continue;
 86
 87		tdomain = scpi_ops->device_domain_id(tcpu_dev);
 88		if (tdomain == domain)
 89			cpumask_set_cpu(cpu, cpumask);
 90	}
 91
 92	return 0;
 93}
 94
 95static int scpi_cpufreq_init(struct cpufreq_policy *policy)
 96{
 97	int ret;
 98	unsigned int latency;
 99	struct device *cpu_dev;
100	struct scpi_data *priv;
101	struct cpufreq_frequency_table *freq_table;
102
103	cpu_dev = get_cpu_device(policy->cpu);
104	if (!cpu_dev) {
105		pr_err("failed to get cpu%d device\n", policy->cpu);
106		return -ENODEV;
107	}
108
109	ret = scpi_ops->add_opps_to_device(cpu_dev);
110	if (ret) {
111		dev_warn(cpu_dev, "failed to add opps to the device\n");
112		return ret;
113	}
114
115	ret = scpi_get_sharing_cpus(cpu_dev, policy->cpus);
116	if (ret) {
117		dev_warn(cpu_dev, "failed to get sharing cpumask\n");
118		return ret;
119	}
120
121	ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
122	if (ret) {
123		dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
124			__func__, ret);
125		return ret;
126	}
127
128	ret = dev_pm_opp_get_opp_count(cpu_dev);
129	if (ret <= 0) {
130		dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
131		ret = -EPROBE_DEFER;
132		goto out_free_opp;
133	}
134
135	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
136	if (!priv) {
137		ret = -ENOMEM;
138		goto out_free_opp;
139	}
140
141	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
142	if (ret) {
143		dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
144		goto out_free_priv;
145	}
146
147	priv->cpu_dev = cpu_dev;
148	priv->clk = clk_get(cpu_dev, NULL);
149	if (IS_ERR(priv->clk)) {
150		dev_err(cpu_dev, "%s: Failed to get clk for cpu: %d\n",
151			__func__, cpu_dev->id);
152		ret = PTR_ERR(priv->clk);
153		goto out_free_cpufreq_table;
154	}
155
156	policy->driver_data = priv;
157	policy->freq_table = freq_table;
158
159	/* scpi allows DVFS request for any domain from any CPU */
160	policy->dvfs_possible_from_any_cpu = true;
161
162	latency = scpi_ops->get_transition_latency(cpu_dev);
163	if (!latency)
164		latency = CPUFREQ_ETERNAL;
165
166	policy->cpuinfo.transition_latency = latency;
167
168	policy->fast_switch_possible = false;
169
170	dev_pm_opp_of_register_em(cpu_dev, policy->cpus);
171
172	return 0;
173
174out_free_cpufreq_table:
175	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
176out_free_priv:
177	kfree(priv);
178out_free_opp:
179	dev_pm_opp_remove_all_dynamic(cpu_dev);
180
181	return ret;
182}
183
184static int scpi_cpufreq_exit(struct cpufreq_policy *policy)
185{
186	struct scpi_data *priv = policy->driver_data;
187
188	clk_put(priv->clk);
189	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
190	dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
191	kfree(priv);
192
193	return 0;
194}
195
196static struct cpufreq_driver scpi_cpufreq_driver = {
197	.name	= "scpi-cpufreq",
198	.flags	= CPUFREQ_STICKY | CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
199		  CPUFREQ_NEED_INITIAL_FREQ_CHECK |
200		  CPUFREQ_IS_COOLING_DEV,
201	.verify	= cpufreq_generic_frequency_table_verify,
202	.attr	= cpufreq_generic_attr,
203	.get	= scpi_cpufreq_get_rate,
204	.init	= scpi_cpufreq_init,
205	.exit	= scpi_cpufreq_exit,
206	.target_index	= scpi_cpufreq_set_target,
207};
208
209static int scpi_cpufreq_probe(struct platform_device *pdev)
210{
211	int ret;
212
213	scpi_ops = get_scpi_ops();
214	if (!scpi_ops)
215		return -EIO;
216
217	ret = cpufreq_register_driver(&scpi_cpufreq_driver);
218	if (ret)
219		dev_err(&pdev->dev, "%s: registering cpufreq failed, err: %d\n",
220			__func__, ret);
221	return ret;
222}
223
224static int scpi_cpufreq_remove(struct platform_device *pdev)
225{
226	cpufreq_unregister_driver(&scpi_cpufreq_driver);
227	scpi_ops = NULL;
228	return 0;
229}
230
231static struct platform_driver scpi_cpufreq_platdrv = {
232	.driver = {
233		.name	= "scpi-cpufreq",
234	},
235	.probe		= scpi_cpufreq_probe,
236	.remove		= scpi_cpufreq_remove,
237};
238module_platform_driver(scpi_cpufreq_platdrv);
239
240MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
241MODULE_DESCRIPTION("ARM SCPI CPUFreq interface driver");
242MODULE_LICENSE("GPL v2");