1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * System Control and Power Interface (SCPI) based CPUFreq Interface driver
4  *
5  * Copyright (C) 2015 ARM Ltd.
6  * Sudeep Holla <sudeep.holla@arm.com>
7  */
8 
9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10 
11 #include <linux/clk.h>
12 #include <linux/cpu.h>
13 #include <linux/cpufreq.h>
14 #include <linux/cpumask.h>
15 #include <linux/export.h>
16 #include <linux/module.h>
17 #include <linux/of_platform.h>
18 #include <linux/pm_opp.h>
19 #include <linux/scpi_protocol.h>
20 #include <linux/slab.h>
21 #include <linux/types.h>
22 
23 struct scpi_data {
24 	struct clk *clk;
25 	struct device *cpu_dev;
26 };
27 
28 static struct scpi_ops *scpi_ops;
29 
30 static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
31 {
32 	struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
33 	struct scpi_data *priv = policy->driver_data;
34 	unsigned long rate = clk_get_rate(priv->clk);
35 
36 	return rate / 1000;
37 }
38 
39 static int
40 scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
41 {
42 	u64 rate = policy->freq_table[index].frequency * 1000;
43 	struct scpi_data *priv = policy->driver_data;
44 	int ret;
45 
46 	ret = clk_set_rate(priv->clk, rate);
47 
48 	if (ret)
49 		return ret;
50 
51 	if (clk_get_rate(priv->clk) != rate)
52 		return -EIO;
53 
54 	return 0;
55 }
56 
57 static int
58 scpi_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
59 {
60 	int cpu, domain, tdomain;
61 	struct device *tcpu_dev;
62 
63 	domain = scpi_ops->device_domain_id(cpu_dev);
64 	if (domain < 0)
65 		return domain;
66 
67 	for_each_possible_cpu(cpu) {
68 		if (cpu == cpu_dev->id)
69 			continue;
70 
71 		tcpu_dev = get_cpu_device(cpu);
72 		if (!tcpu_dev)
73 			continue;
74 
75 		tdomain = scpi_ops->device_domain_id(tcpu_dev);
76 		if (tdomain == domain)
77 			cpumask_set_cpu(cpu, cpumask);
78 	}
79 
80 	return 0;
81 }
82 
83 static int scpi_cpufreq_init(struct cpufreq_policy *policy)
84 {
85 	int ret;
86 	unsigned int latency;
87 	struct device *cpu_dev;
88 	struct scpi_data *priv;
89 	struct cpufreq_frequency_table *freq_table;
90 
91 	cpu_dev = get_cpu_device(policy->cpu);
92 	if (!cpu_dev) {
93 		pr_err("failed to get cpu%d device\n", policy->cpu);
94 		return -ENODEV;
95 	}
96 
97 	ret = scpi_ops->add_opps_to_device(cpu_dev);
98 	if (ret) {
99 		dev_warn(cpu_dev, "failed to add opps to the device\n");
100 		return ret;
101 	}
102 
103 	ret = scpi_get_sharing_cpus(cpu_dev, policy->cpus);
104 	if (ret) {
105 		dev_warn(cpu_dev, "failed to get sharing cpumask\n");
106 		return ret;
107 	}
108 
109 	ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
110 	if (ret) {
111 		dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
112 			__func__, ret);
113 		return ret;
114 	}
115 
116 	ret = dev_pm_opp_get_opp_count(cpu_dev);
117 	if (ret <= 0) {
118 		dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
119 		ret = -EPROBE_DEFER;
120 		goto out_free_opp;
121 	}
122 
123 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
124 	if (!priv) {
125 		ret = -ENOMEM;
126 		goto out_free_opp;
127 	}
128 
129 	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
130 	if (ret) {
131 		dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
132 		goto out_free_priv;
133 	}
134 
135 	priv->cpu_dev = cpu_dev;
136 	priv->clk = clk_get(cpu_dev, NULL);
137 	if (IS_ERR(priv->clk)) {
138 		dev_err(cpu_dev, "%s: Failed to get clk for cpu: %d\n",
139 			__func__, cpu_dev->id);
140 		ret = PTR_ERR(priv->clk);
141 		goto out_free_cpufreq_table;
142 	}
143 
144 	policy->driver_data = priv;
145 	policy->freq_table = freq_table;
146 
147 	/* scpi allows DVFS request for any domain from any CPU */
148 	policy->dvfs_possible_from_any_cpu = true;
149 
150 	latency = scpi_ops->get_transition_latency(cpu_dev);
151 	if (!latency)
152 		latency = CPUFREQ_ETERNAL;
153 
154 	policy->cpuinfo.transition_latency = latency;
155 
156 	policy->fast_switch_possible = false;
157 
158 	return 0;
159 
160 out_free_cpufreq_table:
161 	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
162 out_free_priv:
163 	kfree(priv);
164 out_free_opp:
165 	dev_pm_opp_remove_all_dynamic(cpu_dev);
166 
167 	return ret;
168 }
169 
170 static int scpi_cpufreq_exit(struct cpufreq_policy *policy)
171 {
172 	struct scpi_data *priv = policy->driver_data;
173 
174 	clk_put(priv->clk);
175 	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
176 	dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
177 	kfree(priv);
178 
179 	return 0;
180 }
181 
182 static struct cpufreq_driver scpi_cpufreq_driver = {
183 	.name	= "scpi-cpufreq",
184 	.flags	= CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
185 		  CPUFREQ_NEED_INITIAL_FREQ_CHECK |
186 		  CPUFREQ_IS_COOLING_DEV,
187 	.verify	= cpufreq_generic_frequency_table_verify,
188 	.attr	= cpufreq_generic_attr,
189 	.get	= scpi_cpufreq_get_rate,
190 	.init	= scpi_cpufreq_init,
191 	.exit	= scpi_cpufreq_exit,
192 	.target_index	= scpi_cpufreq_set_target,
193 	.register_em	= cpufreq_register_em_with_opp,
194 };
195 
196 static int scpi_cpufreq_probe(struct platform_device *pdev)
197 {
198 	int ret;
199 
200 	scpi_ops = get_scpi_ops();
201 	if (!scpi_ops)
202 		return -EIO;
203 
204 	ret = cpufreq_register_driver(&scpi_cpufreq_driver);
205 	if (ret)
206 		dev_err(&pdev->dev, "%s: registering cpufreq failed, err: %d\n",
207 			__func__, ret);
208 	return ret;
209 }
210 
211 static int scpi_cpufreq_remove(struct platform_device *pdev)
212 {
213 	cpufreq_unregister_driver(&scpi_cpufreq_driver);
214 	scpi_ops = NULL;
215 	return 0;
216 }
217 
218 static struct platform_driver scpi_cpufreq_platdrv = {
219 	.driver = {
220 		.name	= "scpi-cpufreq",
221 	},
222 	.probe		= scpi_cpufreq_probe,
223 	.remove		= scpi_cpufreq_remove,
224 };
225 module_platform_driver(scpi_cpufreq_platdrv);
226 
227 MODULE_ALIAS("platform:scpi-cpufreq");
228 MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
229 MODULE_DESCRIPTION("ARM SCPI CPUFreq interface driver");
230 MODULE_LICENSE("GPL v2");
231