drivers/cpufreq/raspberrypi-cpufreq.c

   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 int 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         return 0;
  79 }
  80
  81 /*
  82  * Since the driver depends on clk-raspberrypi, which may return EPROBE_DEFER,
  83  * all the activity is performed in the probe, which may be defered as well.
  84  */
  85 static struct platform_driver raspberrypi_cpufreq_driver = {
  86         .driver = {
  87                 .name = "raspberrypi-cpufreq",
  88         },
  89         .probe          = raspberrypi_cpufreq_probe,
  90         .remove         = raspberrypi_cpufreq_remove,
  91 };
  92 module_platform_driver(raspberrypi_cpufreq_driver);
  93
  94 MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de");
  95 MODULE_DESCRIPTION("Raspberry Pi cpufreq driver");
  96 MODULE_LICENSE("GPL");
  97 MODULE_ALIAS("platform:raspberrypi-cpufreq");