LXR linux/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
  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(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
  62remove_opp:
  63        dev_pm_opp_remove_all_dynamic(cpu_dev);
  64
  65        return ret;
  66}
  67
  68static 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 */
  85static struct platform_driver raspberrypi_cpufreq_driver = {
  86        .driver = {
  87                .name = "raspberrypi-cpufreq",
  88        },
  89        .probe          = raspberrypi_cpufreq_probe,
  90        .remove         = raspberrypi_cpufreq_remove,
  91};
  92module_platform_driver(raspberrypi_cpufreq_driver);
  93
  94MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de");
  95MODULE_DESCRIPTION("Raspberry Pi cpufreq driver");
  96MODULE_LICENSE("GPL");
  97MODULE_ALIAS("platform:raspberrypi-cpufreq");
  98