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Commit d3df18a9 authored by Nicolas Saenz Julienne's avatar Nicolas Saenz Julienne Committed by Viresh Kumar
Browse files

cpufreq: add driver for Raspberry Pi 



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: default avatarNicolas Saenz Julienne <nsaenzjulienne@suse.de>
Acked-by: default avatarEric Anholt <eric@anholt.net>
Reviewed-by: default avatarStephen Boyd <sboyd@kernel.org>
Acked-by: default avatarStefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
parent e6abacab

drivers/cpufreq/Kconfig.arm

+8 −0
Original line number Diff line number Diff line
@@ -141,6 +141,14 @@ config ARM_QCOM_CPUFREQ_HW 
	  The driver implements the cpufreq interface for this HW engine.

	  Say Y if you want to support CPUFreq HW.



config ARM_RASPBERRYPI_CPUFREQ

	tristate "Raspberry Pi cpufreq support"

	depends on CLK_RASPBERRYPI || COMPILE_TEST

	help

	  This adds the CPUFreq driver for Raspberry Pi



	  If in doubt, say N.



config ARM_S3C_CPUFREQ

	bool

	help

drivers/cpufreq/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -65,6 +65,7 @@ obj-$(CONFIG_ARM_PXA2xx_CPUFREQ) += pxa2xx-cpufreq.o 
obj-$(CONFIG_PXA3xx)			+= pxa3xx-cpufreq.o

obj-$(CONFIG_ARM_QCOM_CPUFREQ_HW)	+= qcom-cpufreq-hw.o

obj-$(CONFIG_ARM_QCOM_CPUFREQ_KRYO)	+= qcom-cpufreq-kryo.o

obj-$(CONFIG_ARM_RASPBERRYPI_CPUFREQ) 	+= raspberrypi-cpufreq.o

obj-$(CONFIG_ARM_S3C2410_CPUFREQ)	+= s3c2410-cpufreq.o

obj-$(CONFIG_ARM_S3C2412_CPUFREQ)	+= s3c2412-cpufreq.o

obj-$(CONFIG_ARM_S3C2416_CPUFREQ)	+= s3c2416-cpufreq.o

drivers/cpufreq/raspberrypi-cpufreq.c

0 → 100644
+97 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * Raspberry Pi cpufreq driver

 *

 * Copyright (C) 2019, Nicolas Saenz Julienne <nsaenzjulienne@suse.de>

 */



#include <linux/clk.h>

#include <linux/cpu.h>

#include <linux/cpufreq.h>

#include <linux/module.h>

#include <linux/platform_device.h>

#include <linux/pm_opp.h>



#define RASPBERRYPI_FREQ_INTERVAL	100000000



static struct platform_device *cpufreq_dt;



static int raspberrypi_cpufreq_probe(struct platform_device *pdev)

{

	struct device *cpu_dev;

	unsigned long min, max;

	unsigned long rate;

	struct clk *clk;

	int ret;



	cpu_dev = get_cpu_device(0);

	if (!cpu_dev) {

		pr_err("Cannot get CPU for cpufreq driver\n");

		return -ENODEV;

	}



	clk = clk_get(cpu_dev, NULL);

	if (IS_ERR(clk)) {

		dev_err(cpu_dev, "Cannot get clock for CPU0\n");

		return PTR_ERR(clk);

	}



	/*

	 * The max and min frequencies are configurable in the Raspberry Pi

	 * firmware, so we query them at runtime.

	 */

	min = roundup(clk_round_rate(clk, 0), RASPBERRYPI_FREQ_INTERVAL);

	max = roundup(clk_round_rate(clk, ULONG_MAX), RASPBERRYPI_FREQ_INTERVAL);

	clk_put(clk);



	for (rate = min; rate <= max; rate += RASPBERRYPI_FREQ_INTERVAL) {

		ret = dev_pm_opp_add(cpu_dev, rate, 0);

		if (ret)

			goto remove_opp;

	}



	cpufreq_dt = platform_device_register_simple("cpufreq-dt", -1, NULL, 0);

	ret = PTR_ERR_OR_ZERO(cpufreq_dt);

	if (ret) {

		dev_err(cpu_dev, "Failed to create platform device, %d\n", ret);

		goto remove_opp;

	}



	return 0;



remove_opp:

	dev_pm_opp_remove_all_dynamic(cpu_dev);



	return ret;

}



static int raspberrypi_cpufreq_remove(struct platform_device *pdev)

{

	struct device *cpu_dev;



	cpu_dev = get_cpu_device(0);

	if (cpu_dev)

		dev_pm_opp_remove_all_dynamic(cpu_dev);



	platform_device_unregister(cpufreq_dt);



	return 0;

}



/*

 * Since the driver depends on clk-raspberrypi, which may return EPROBE_DEFER,

 * all the activity is performed in the probe, which may be defered as well.

 */

static struct platform_driver raspberrypi_cpufreq_driver = {

	.driver = {

		.name = "raspberrypi-cpufreq",

	},

	.probe          = raspberrypi_cpufreq_probe,

	.remove		= raspberrypi_cpufreq_remove,

};

module_platform_driver(raspberrypi_cpufreq_driver);



MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de");

MODULE_DESCRIPTION("Raspberry Pi cpufreq driver");

MODULE_LICENSE("GPL");

MODULE_ALIAS("platform:raspberrypi-cpufreq");