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
17static struct platform_device *cpufreq_dt;
18
19static 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(cpu: 0);
28 if (!cpu_dev) {
29 pr_err("Cannot get CPU for cpufreq driver\n");
30 return -ENODEV;
31 }
32
33 clk = clk_get(dev: cpu_dev, NULL);
34 if (IS_ERR(ptr: clk)) {
35 dev_err(cpu_dev, "Cannot get clock for CPU0\n");
36 return PTR_ERR(ptr: 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(dev: cpu_dev, freq: rate, u_volt: 0);
49 if (ret)
50 goto remove_opp;
51 }
52
53 cpufreq_dt = platform_device_register_simple(name: "cpufreq-dt", id: -1, NULL, num: 0);
54 ret = PTR_ERR_OR_ZERO(ptr: 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
62remove_opp:
63 dev_pm_opp_remove_all_dynamic(dev: cpu_dev);
64
65 return ret;
66}
67
68static void raspberrypi_cpufreq_remove(struct platform_device *pdev)
69{
70 struct device *cpu_dev;
71
72 cpu_dev = get_cpu_device(cpu: 0);
73 if (cpu_dev)
74 dev_pm_opp_remove_all_dynamic(dev: 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 */
83static 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};
90module_platform_driver(raspberrypi_cpufreq_driver);
91
92MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de");
93MODULE_DESCRIPTION("Raspberry Pi cpufreq driver");
94MODULE_LICENSE("GPL");
95MODULE_ALIAS("platform:raspberrypi-cpufreq");
96

source code of linux/drivers/cpufreq/raspberrypi-cpufreq.c