1/*
  2 * System Control and Power Interface (SCPI) based CPUFreq Interface driver
  3 *
  4 * It provides necessary ops to arm_big_little cpufreq driver.
  5 *
  6 * Copyright (C) 2015 ARM Ltd.
  7 * Sudeep Holla <sudeep.holla@arm.com>
  8 *
  9 * This program is free software; you can redistribute it and/or modify
 10 * it under the terms of the GNU General Public License version 2 as
 11 * published by the Free Software Foundation.
 12 *
 13 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 14 * kind, whether express or implied; without even the implied warranty
 15 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 16 * GNU General Public License for more details.
 17 */
 18
 19#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 20
 21#include <linux/clk.h>
 22#include <linux/cpu.h>
 23#include <linux/cpufreq.h>
 24#include <linux/cpumask.h>
 25#include <linux/export.h>
 26#include <linux/module.h>
 27#include <linux/of_platform.h>
 28#include <linux/pm_opp.h>
 29#include <linux/scpi_protocol.h>
 30#include <linux/slab.h>
 31#include <linux/types.h>
 32
 33struct scpi_data {
 34	struct clk *clk;
 35	struct device *cpu_dev;
 36};
 37
 38static struct scpi_ops *scpi_ops;
 39
 40static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
 41{
 42	struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
 43	struct scpi_data *priv = policy->driver_data;
 44	unsigned long rate = clk_get_rate(priv->clk);
 45
 46	return rate / 1000;
 47}
 48
 49static int
 50scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
 51{
 52	unsigned long freq = policy->freq_table[index].frequency;
 53	struct scpi_data *priv = policy->driver_data;
 54	u64 rate = freq * 1000;
 55	int ret;
 56
 57	ret = clk_set_rate(priv->clk, rate);
 58
 59	if (ret)
 60		return ret;
 61
 62	if (clk_get_rate(priv->clk) != rate)
 63		return -EIO;
 64
 65	arch_set_freq_scale(policy->related_cpus, freq,
 66			    policy->cpuinfo.max_freq);
 67
 68	return 0;
 69}
 70
 71static int
 72scpi_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
 73{
 74	int cpu, domain, tdomain;
 75	struct device *tcpu_dev;
 76
 77	domain = scpi_ops->device_domain_id(cpu_dev);
 78	if (domain < 0)
 79		return domain;
 80
 81	for_each_possible_cpu(cpu) {
 82		if (cpu == cpu_dev->id)
 83			continue;
 84
 85		tcpu_dev = get_cpu_device(cpu);
 86		if (!tcpu_dev)
 87			continue;
 88
 89		tdomain = scpi_ops->device_domain_id(tcpu_dev);
 90		if (tdomain == domain)
 91			cpumask_set_cpu(cpu, cpumask);
 92	}
 93
 94	return 0;
 95}
 96
 97static int scpi_cpufreq_init(struct cpufreq_policy *policy)
 98{
 99	int ret;
100	unsigned int latency;
101	struct device *cpu_dev;
102	struct scpi_data *priv;
103	struct cpufreq_frequency_table *freq_table;
104
105	cpu_dev = get_cpu_device(policy->cpu);
106	if (!cpu_dev) {
107		pr_err("failed to get cpu%d device\n", policy->cpu);
108		return -ENODEV;
109	}
110
111	ret = scpi_ops->add_opps_to_device(cpu_dev);
112	if (ret) {
113		dev_warn(cpu_dev, "failed to add opps to the device\n");
114		return ret;
115	}
116
117	ret = scpi_get_sharing_cpus(cpu_dev, policy->cpus);
118	if (ret) {
119		dev_warn(cpu_dev, "failed to get sharing cpumask\n");
120		return ret;
121	}
122
123	ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
124	if (ret) {
125		dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
126			__func__, ret);
127		return ret;
128	}
129
130	ret = dev_pm_opp_get_opp_count(cpu_dev);
131	if (ret <= 0) {
132		dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
133		ret = -EPROBE_DEFER;
134		goto out_free_opp;
135	}
136
137	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
138	if (!priv) {
139		ret = -ENOMEM;
140		goto out_free_opp;
141	}
142
143	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
144	if (ret) {
145		dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
146		goto out_free_priv;
147	}
148
149	priv->cpu_dev = cpu_dev;
150	priv->clk = clk_get(cpu_dev, NULL);
151	if (IS_ERR(priv->clk)) {
152		dev_err(cpu_dev, "%s: Failed to get clk for cpu: %d\n",
153			__func__, cpu_dev->id);
154		ret = PTR_ERR(priv->clk);
155		goto out_free_cpufreq_table;
156	}
157
158	policy->driver_data = priv;
159	policy->freq_table = freq_table;
160
161	/* scpi allows DVFS request for any domain from any CPU */
162	policy->dvfs_possible_from_any_cpu = true;
163
164	latency = scpi_ops->get_transition_latency(cpu_dev);
165	if (!latency)
166		latency = CPUFREQ_ETERNAL;
167
168	policy->cpuinfo.transition_latency = latency;
169
170	policy->fast_switch_possible = false;
171
172	dev_pm_opp_of_register_em(policy->cpus);
173
174	return 0;
175
176out_free_cpufreq_table:
177	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
178out_free_priv:
179	kfree(priv);
180out_free_opp:
181	dev_pm_opp_remove_all_dynamic(cpu_dev);
182
183	return ret;
184}
185
186static int scpi_cpufreq_exit(struct cpufreq_policy *policy)
187{
188	struct scpi_data *priv = policy->driver_data;
189
190	clk_put(priv->clk);
191	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
192	dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
193	kfree(priv);
194
195	return 0;
196}
197
198static struct cpufreq_driver scpi_cpufreq_driver = {
199	.name	= "scpi-cpufreq",
200	.flags	= CPUFREQ_STICKY | CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
201		  CPUFREQ_NEED_INITIAL_FREQ_CHECK |
202		  CPUFREQ_IS_COOLING_DEV,
203	.verify	= cpufreq_generic_frequency_table_verify,
204	.attr	= cpufreq_generic_attr,
205	.get	= scpi_cpufreq_get_rate,
206	.init	= scpi_cpufreq_init,
207	.exit	= scpi_cpufreq_exit,
208	.target_index	= scpi_cpufreq_set_target,
209};
210
211static int scpi_cpufreq_probe(struct platform_device *pdev)
212{
213	int ret;
214
215	scpi_ops = get_scpi_ops();
216	if (!scpi_ops)
217		return -EIO;
218
219	ret = cpufreq_register_driver(&scpi_cpufreq_driver);
220	if (ret)
221		dev_err(&pdev->dev, "%s: registering cpufreq failed, err: %d\n",
222			__func__, ret);
223	return ret;
224}
225
226static int scpi_cpufreq_remove(struct platform_device *pdev)
227{
228	cpufreq_unregister_driver(&scpi_cpufreq_driver);
229	scpi_ops = NULL;
230	return 0;
231}
232
233static struct platform_driver scpi_cpufreq_platdrv = {
234	.driver = {
235		.name	= "scpi-cpufreq",
236	},
237	.probe		= scpi_cpufreq_probe,
238	.remove		= scpi_cpufreq_remove,
239};
240module_platform_driver(scpi_cpufreq_platdrv);
241
242MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
243MODULE_DESCRIPTION("ARM SCPI CPUFreq interface driver");
244MODULE_LICENSE("GPL v2");