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Raspberry Pi's firmware offers and interface though which update it's performance requirements. It allows us to request for specific runtime frequencies, which the firmware might or might not respect, depending on the firmware configuration and thermals. As the maximum and minimum frequencies are configurable in the firmware there is no way to know in advance their values. So the Raspberry Pi cpufreq driver queries them, builds an opp frequency table to then launch cpufreq-dt. Also, as the firmware interface might be configured as a module, making the cpu clock unavailable during init, this implements a full fledged driver, as opposed to most drivers registering cpufreq-dt, which only make use of an init routine. Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> Acked-by: Eric Anholt <eric@anholt.net> Reviewed-by: Stephen Boyd <sboyd@kernel.org> Acked-by: Stefan Wahren <stefan.wahren@i2se.com> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
98 lines
2.3 KiB
C
98 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Raspberry Pi cpufreq driver
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*
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* Copyright (C) 2019, Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
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*/
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#include <linux/clk.h>
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#include <linux/cpu.h>
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#include <linux/cpufreq.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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#include <linux/pm_opp.h>
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#define RASPBERRYPI_FREQ_INTERVAL 100000000
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static struct platform_device *cpufreq_dt;
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static int raspberrypi_cpufreq_probe(struct platform_device *pdev)
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{
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struct device *cpu_dev;
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unsigned long min, max;
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unsigned long rate;
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struct clk *clk;
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int ret;
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cpu_dev = get_cpu_device(0);
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if (!cpu_dev) {
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pr_err("Cannot get CPU for cpufreq driver\n");
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return -ENODEV;
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}
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clk = clk_get(cpu_dev, NULL);
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if (IS_ERR(clk)) {
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dev_err(cpu_dev, "Cannot get clock for CPU0\n");
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return PTR_ERR(clk);
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}
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/*
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* The max and min frequencies are configurable in the Raspberry Pi
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* firmware, so we query them at runtime.
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*/
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min = roundup(clk_round_rate(clk, 0), RASPBERRYPI_FREQ_INTERVAL);
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max = roundup(clk_round_rate(clk, ULONG_MAX), RASPBERRYPI_FREQ_INTERVAL);
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clk_put(clk);
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for (rate = min; rate <= max; rate += RASPBERRYPI_FREQ_INTERVAL) {
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ret = dev_pm_opp_add(cpu_dev, rate, 0);
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if (ret)
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goto remove_opp;
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}
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cpufreq_dt = platform_device_register_simple("cpufreq-dt", -1, NULL, 0);
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ret = PTR_ERR_OR_ZERO(cpufreq_dt);
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if (ret) {
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dev_err(cpu_dev, "Failed to create platform device, %d\n", ret);
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goto remove_opp;
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}
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return 0;
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remove_opp:
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dev_pm_opp_remove_all_dynamic(cpu_dev);
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return ret;
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}
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static int raspberrypi_cpufreq_remove(struct platform_device *pdev)
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{
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struct device *cpu_dev;
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cpu_dev = get_cpu_device(0);
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if (cpu_dev)
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dev_pm_opp_remove_all_dynamic(cpu_dev);
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platform_device_unregister(cpufreq_dt);
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return 0;
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}
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/*
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* Since the driver depends on clk-raspberrypi, which may return EPROBE_DEFER,
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* all the activity is performed in the probe, which may be defered as well.
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*/
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static struct platform_driver raspberrypi_cpufreq_driver = {
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.driver = {
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.name = "raspberrypi-cpufreq",
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},
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.probe = raspberrypi_cpufreq_probe,
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.remove = raspberrypi_cpufreq_remove,
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};
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module_platform_driver(raspberrypi_cpufreq_driver);
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MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de");
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MODULE_DESCRIPTION("Raspberry Pi cpufreq driver");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("platform:raspberrypi-cpufreq");
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