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	u64 rate = policy->freq_table[index].frequency * 1000;
 51	struct scpi_data *priv = policy->driver_data;
 52	int ret;
 53
 54	ret = clk_set_rate(priv->clk, rate);
 55
 56	if (ret)
 57		return ret;
 58
 59	if (clk_get_rate(priv->clk) != rate)
 60		return -EIO;
 61
 62	return 0;
 63}
 64
 65static int
 66scpi_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
 67{
 68	int cpu, domain, tdomain;
 69	struct device *tcpu_dev;
 70
 71	domain = scpi_ops->device_domain_id(cpu_dev);
 72	if (domain < 0)
 73		return domain;
 74
 75	for_each_possible_cpu(cpu) {
 76		if (cpu == cpu_dev->id)
 77			continue;
 78
 79		tcpu_dev = get_cpu_device(cpu);
 80		if (!tcpu_dev)
 81			continue;
 82
 83		tdomain = scpi_ops->device_domain_id(tcpu_dev);
 84		if (tdomain == domain)
 85			cpumask_set_cpu(cpu, cpumask);
 86	}
 87
 88	return 0;
 89}
 90
 91static int scpi_cpufreq_init(struct cpufreq_policy *policy)
 92{
 93	int ret;
 94	unsigned int latency;
 95	struct device *cpu_dev;
 96	struct scpi_data *priv;
 97	struct cpufreq_frequency_table *freq_table;
 98
 99	cpu_dev = get_cpu_device(policy->cpu);
100	if (!cpu_dev) {
101		pr_err("failed to get cpu%d device\n", policy->cpu);
102		return -ENODEV;
103	}
104
105	ret = scpi_ops->add_opps_to_device(cpu_dev);
106	if (ret) {
107		dev_warn(cpu_dev, "failed to add opps to the device\n");
108		return ret;
109	}
110
111	ret = scpi_get_sharing_cpus(cpu_dev, policy->cpus);
112	if (ret) {
113		dev_warn(cpu_dev, "failed to get sharing cpumask\n");
114		return ret;
115	}
116
117	ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
118	if (ret) {
119		dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
120			__func__, ret);
121		return ret;
122	}
123
124	ret = dev_pm_opp_get_opp_count(cpu_dev);
125	if (ret <= 0) {
126		dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
127		ret = -EPROBE_DEFER;
128		goto out_free_opp;
129	}
130
131	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
132	if (!priv) {
133		ret = -ENOMEM;
134		goto out_free_opp;
135	}
136
137	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
138	if (ret) {
139		dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
140		goto out_free_priv;
141	}
142
143	priv->cpu_dev = cpu_dev;
144	priv->clk = clk_get(cpu_dev, NULL);
145	if (IS_ERR(priv->clk)) {
146		dev_err(cpu_dev, "%s: Failed to get clk for cpu: %d\n",
147			__func__, cpu_dev->id);
148		ret = PTR_ERR(priv->clk);
149		goto out_free_cpufreq_table;
150	}
151
152	policy->driver_data = priv;
153	policy->freq_table = freq_table;
154
155	/* scpi allows DVFS request for any domain from any CPU */
156	policy->dvfs_possible_from_any_cpu = true;
157
158	latency = scpi_ops->get_transition_latency(cpu_dev);
159	if (!latency)
160		latency = CPUFREQ_ETERNAL;
161
162	policy->cpuinfo.transition_latency = latency;
163
164	policy->fast_switch_possible = false;
165
166	dev_pm_opp_of_register_em(cpu_dev, policy->cpus);
167
168	return 0;
169
170out_free_cpufreq_table:
171	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
172out_free_priv:
173	kfree(priv);
174out_free_opp:
175	dev_pm_opp_remove_all_dynamic(cpu_dev);
176
177	return ret;
178}
179
180static int scpi_cpufreq_exit(struct cpufreq_policy *policy)
181{
182	struct scpi_data *priv = policy->driver_data;
183
184	clk_put(priv->clk);
185	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
186	dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
187	kfree(priv);
188
189	return 0;
190}
191
192static struct cpufreq_driver scpi_cpufreq_driver = {
193	.name	= "scpi-cpufreq",
194	.flags	= CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
195		  CPUFREQ_NEED_INITIAL_FREQ_CHECK |
196		  CPUFREQ_IS_COOLING_DEV,
197	.verify	= cpufreq_generic_frequency_table_verify,
198	.attr	= cpufreq_generic_attr,
199	.get	= scpi_cpufreq_get_rate,
200	.init	= scpi_cpufreq_init,
201	.exit	= scpi_cpufreq_exit,
202	.target_index	= scpi_cpufreq_set_target,
203};
204
205static int scpi_cpufreq_probe(struct platform_device *pdev)
206{
207	int ret;
208
209	scpi_ops = get_scpi_ops();
210	if (!scpi_ops)
211		return -EIO;
212
213	ret = cpufreq_register_driver(&scpi_cpufreq_driver);
214	if (ret)
215		dev_err(&pdev->dev, "%s: registering cpufreq failed, err: %d\n",
216			__func__, ret);
217	return ret;
218}
219
220static int scpi_cpufreq_remove(struct platform_device *pdev)
221{
222	cpufreq_unregister_driver(&scpi_cpufreq_driver);
223	scpi_ops = NULL;
224	return 0;
225}
226
227static struct platform_driver scpi_cpufreq_platdrv = {
228	.driver = {
229		.name	= "scpi-cpufreq",
230	},
231	.probe		= scpi_cpufreq_probe,
232	.remove		= scpi_cpufreq_remove,
233};
234module_platform_driver(scpi_cpufreq_platdrv);
235
236MODULE_ALIAS("platform:scpi-cpufreq");
237MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
238MODULE_DESCRIPTION("ARM SCPI CPUFreq interface driver");
239MODULE_LICENSE("GPL v2");