1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Raspberry Pi cpufreq driver
4  *
5  * Copyright (C) 2019, Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
6  */
7 
8 #include <linux/clk.h>
9 #include <linux/cpu.h>
10 #include <linux/cpufreq.h>
11 #include <linux/module.h>
12 #include <linux/platform_device.h>
13 #include <linux/pm_opp.h>
14 
15 #define RASPBERRYPI_FREQ_INTERVAL	100000000
16 
17 static struct platform_device *cpufreq_dt;
18 
19 static int raspberrypi_cpufreq_probe(struct platform_device *pdev)
20 {
21 	struct device *cpu_dev;
22 	unsigned long min, max;
23 	unsigned long rate;
24 	struct clk *clk;
25 	int ret;
26 
27 	cpu_dev = get_cpu_device(0);
28 	if (!cpu_dev) {
29 		pr_err("Cannot get CPU for cpufreq driver\n");
30 		return -ENODEV;
31 	}
32 
33 	clk = clk_get(cpu_dev, NULL);
34 	if (IS_ERR(clk)) {
35 		dev_err(cpu_dev, "Cannot get clock for CPU0\n");
36 		return PTR_ERR(clk);
37 	}
38 
39 	/*
40 	 * The max and min frequencies are configurable in the Raspberry Pi
41 	 * firmware, so we query them at runtime.
42 	 */
43 	min = roundup(clk_round_rate(clk, 0), RASPBERRYPI_FREQ_INTERVAL);
44 	max = roundup(clk_round_rate(clk, ULONG_MAX), RASPBERRYPI_FREQ_INTERVAL);
45 	clk_put(clk);
46 
47 	for (rate = min; rate <= max; rate += RASPBERRYPI_FREQ_INTERVAL) {
48 		ret = dev_pm_opp_add(cpu_dev, rate, 0);
49 		if (ret)
50 			goto remove_opp;
51 	}
52 
53 	cpufreq_dt = platform_device_register_simple("cpufreq-dt", -1, NULL, 0);
54 	ret = PTR_ERR_OR_ZERO(cpufreq_dt);
55 	if (ret) {
56 		dev_err(cpu_dev, "Failed to create platform device, %d\n", ret);
57 		goto remove_opp;
58 	}
59 
60 	return 0;
61 
62 remove_opp:
63 	dev_pm_opp_remove_all_dynamic(cpu_dev);
64 
65 	return ret;
66 }
67 
68 static void raspberrypi_cpufreq_remove(struct platform_device *pdev)
69 {
70 	struct device *cpu_dev;
71 
72 	cpu_dev = get_cpu_device(0);
73 	if (cpu_dev)
74 		dev_pm_opp_remove_all_dynamic(cpu_dev);
75 
76 	platform_device_unregister(cpufreq_dt);
77 }
78 
79 /*
80  * Since the driver depends on clk-raspberrypi, which may return EPROBE_DEFER,
81  * all the activity is performed in the probe, which may be defered as well.
82  */
83 static struct platform_driver raspberrypi_cpufreq_driver = {
84 	.driver = {
85 		.name = "raspberrypi-cpufreq",
86 	},
87 	.probe          = raspberrypi_cpufreq_probe,
88 	.remove_new	= raspberrypi_cpufreq_remove,
89 };
90 module_platform_driver(raspberrypi_cpufreq_driver);
91 
92 MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de");
93 MODULE_DESCRIPTION("Raspberry Pi cpufreq driver");
94 MODULE_LICENSE("GPL");
95 MODULE_ALIAS("platform:raspberrypi-cpufreq");
96