tegra30-devfreq.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * A devfreq driver for NVIDIA Tegra SoCs
 *
 * Copyright (c) 2014 NVIDIA CORPORATION. All rights reserved.
 * Copyright (C) 2014 Google, Inc
 */

#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/devfreq.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
#include <linux/reset.h>
#include <linux/workqueue.h>

#include "governor.h"

#define ACTMON_GLB_STATUS					0x0
#define ACTMON_GLB_PERIOD_CTRL					0x4

#define ACTMON_DEV_CTRL						0x0
#define ACTMON_DEV_CTRL_K_VAL_SHIFT				10
#define ACTMON_DEV_CTRL_ENB_PERIODIC				BIT(18)
#define ACTMON_DEV_CTRL_AVG_BELOW_WMARK_EN			BIT(20)
#define ACTMON_DEV_CTRL_AVG_ABOVE_WMARK_EN			BIT(21)
#define ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_NUM_SHIFT	23
#define ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_NUM_SHIFT	26
#define ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN		BIT(29)
#define ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN		BIT(30)
#define ACTMON_DEV_CTRL_ENB					BIT(31)

#define ACTMON_DEV_CTRL_STOP					0x00000000

#define ACTMON_DEV_UPPER_WMARK					0x4
#define ACTMON_DEV_LOWER_WMARK					0x8
#define ACTMON_DEV_INIT_AVG					0xc
#define ACTMON_DEV_AVG_UPPER_WMARK				0x10
#define ACTMON_DEV_AVG_LOWER_WMARK				0x14
#define ACTMON_DEV_COUNT_WEIGHT					0x18
#define ACTMON_DEV_AVG_COUNT					0x20
#define ACTMON_DEV_INTR_STATUS					0x24

#define ACTMON_INTR_STATUS_CLEAR				0xffffffff

#define ACTMON_DEV_INTR_CONSECUTIVE_UPPER			BIT(31)
#define ACTMON_DEV_INTR_CONSECUTIVE_LOWER			BIT(30)

#define ACTMON_ABOVE_WMARK_WINDOW				1
#define ACTMON_BELOW_WMARK_WINDOW				3
#define ACTMON_BOOST_FREQ_STEP					16000

/*
 * Activity counter is incremented every 256 memory transactions, and each
 * transaction takes 4 EMC clocks for Tegra124; So the COUNT_WEIGHT is
 * 4 * 256 = 1024.
 */
#define ACTMON_COUNT_WEIGHT					0x400

/*
 * ACTMON_AVERAGE_WINDOW_LOG2: default value for @DEV_CTRL_K_VAL, which
 * translates to 2 ^ (K_VAL + 1). ex: 2 ^ (6 + 1) = 128
 */
#define ACTMON_AVERAGE_WINDOW_LOG2			6
#define ACTMON_SAMPLING_PERIOD				12 /* ms */
#define ACTMON_DEFAULT_AVG_BAND				6  /* 1/10 of % */

#define KHZ							1000

#define KHZ_MAX						(ULONG_MAX / KHZ)

/* Assume that the bus is saturated if the utilization is 25% */
#define BUS_SATURATION_RATIO					25

/**
 * struct tegra_devfreq_device_config - configuration specific to an ACTMON
 * device
 *
 * Coefficients and thresholds are percentages unless otherwise noted
 */
struct tegra_devfreq_device_config {
	u32		offset;
	u32		irq_mask;

	/* Factors applied to boost_freq every consecutive watermark breach */
	unsigned int	boost_up_coeff;
	unsigned int	boost_down_coeff;

	/* Define the watermark bounds when applied to the current avg */
	unsigned int	boost_up_threshold;
	unsigned int	boost_down_threshold;

	/*
	 * Threshold of activity (cycles translated to kHz) below which the
	 * CPU frequency isn't to be taken into account. This is to avoid
	 * increasing the EMC frequency when the CPU is very busy but not
	 * accessing the bus often.
	 */
	u32		avg_dependency_threshold;
};

enum tegra_actmon_device {
	MCALL = 0,
	MCCPU,
};

static const struct tegra_devfreq_device_config actmon_device_configs[] = {
	{
		/* MCALL: All memory accesses (including from the CPUs) */
		.offset = 0x1c0,
		.irq_mask = 1 << 26,
		.boost_up_coeff = 200,
		.boost_down_coeff = 50,
		.boost_up_threshold = 60,
		.boost_down_threshold = 40,
	},
	{
		/* MCCPU: memory accesses from the CPUs */
		.offset = 0x200,
		.irq_mask = 1 << 25,
		.boost_up_coeff = 800,
		.boost_down_coeff = 40,
		.boost_up_threshold = 27,
		.boost_down_threshold = 10,
		.avg_dependency_threshold = 16000, /* 16MHz in kHz units */
	},
};

/**
 * struct tegra_devfreq_device - state specific to an ACTMON device
 *
 * Frequencies are in kHz.
 */
struct tegra_devfreq_device {
	const struct tegra_devfreq_device_config *config;
	void __iomem *regs;

	/* Average event count sampled in the last interrupt */
	u32 avg_count;

	/*
	 * Extra frequency to increase the target by due to consecutive
	 * watermark breaches.
	 */
	unsigned long boost_freq;

	/* Optimal frequency calculated from the stats for this device */
	unsigned long target_freq;
};

struct tegra_devfreq {
	struct devfreq		*devfreq;

	struct reset_control	*reset;
	struct clk		*clock;
	void __iomem		*regs;

	struct clk		*emc_clock;
	unsigned long		max_freq;
	unsigned long		cur_freq;
	struct notifier_block	clk_rate_change_nb;

	struct delayed_work	cpufreq_update_work;
	struct notifier_block	cpu_rate_change_nb;

	struct tegra_devfreq_device devices[ARRAY_SIZE(actmon_device_configs)];

	unsigned int		irq;

	bool			started;
};

struct tegra_actmon_emc_ratio {
	unsigned long cpu_freq;
	unsigned long emc_freq;
};

static const struct tegra_actmon_emc_ratio actmon_emc_ratios[] = {
	{ 1400000,    KHZ_MAX },
	{ 1200000,    750000 },
	{ 1100000,    600000 },
	{ 1000000,    500000 },
	{  800000,    375000 },
	{  500000,    200000 },
	{  250000,    100000 },
};

static u32 actmon_readl(struct tegra_devfreq *tegra, u32 offset)
{
	return readl_relaxed(tegra->regs + offset);
}

static void actmon_writel(struct tegra_devfreq *tegra, u32 val, u32 offset)
{
	writel_relaxed(val, tegra->regs + offset);
}

static u32 device_readl(struct tegra_devfreq_device *dev, u32 offset)
{
	return readl_relaxed(dev->regs + offset);
}

static void device_writel(struct tegra_devfreq_device *dev, u32 val,
			  u32 offset)
{
	writel_relaxed(val, dev->regs + offset);
}

static unsigned long do_percent(unsigned long long val, unsigned int pct)
{
	val = val * pct;
	do_div(val, 100);

	/*
	 * High freq + high boosting percent + large polling interval are
	 * resulting in integer overflow when watermarks are calculated.
	 */
	return min_t(u64, val, U32_MAX);
}

static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra,
					   struct tegra_devfreq_device *dev)
{
	u32 avg_band_freq = tegra->max_freq * ACTMON_DEFAULT_AVG_BAND / KHZ;
	u32 band = avg_band_freq * tegra->devfreq->profile->polling_ms;
	u32 avg;

	avg = min(dev->avg_count, U32_MAX - band);
	device_writel(dev, avg + band, ACTMON_DEV_AVG_UPPER_WMARK);

	avg = max(dev->avg_count, band);
	device_writel(dev, avg - band, ACTMON_DEV_AVG_LOWER_WMARK);
}

static void tegra_devfreq_update_wmark(struct tegra_devfreq *tegra,
				       struct tegra_devfreq_device *dev)
{
	u32 val = tegra->cur_freq * tegra->devfreq->profile->polling_ms;

	device_writel(dev, do_percent(val, dev->config->boost_up_threshold),
		      ACTMON_DEV_UPPER_WMARK);

	device_writel(dev, do_percent(val, dev->config->boost_down_threshold),
		      ACTMON_DEV_LOWER_WMARK);
}

static void actmon_isr_device(struct tegra_devfreq *tegra,
			      struct tegra_devfreq_device *dev)
{
	u32 intr_status, dev_ctrl;

	dev->avg_count = device_readl(dev, ACTMON_DEV_AVG_COUNT);
	tegra_devfreq_update_avg_wmark(tegra, dev);

	intr_status = device_readl(dev, ACTMON_DEV_INTR_STATUS);
	dev_ctrl = device_readl(dev, ACTMON_DEV_CTRL);

	if (intr_status & ACTMON_DEV_INTR_CONSECUTIVE_UPPER) {
		/*
		 * new_boost = min(old_boost * up_coef + step, max_freq)
		 */
		dev->boost_freq = do_percent(dev->boost_freq,
					     dev->config->boost_up_coeff);
		dev->boost_freq += ACTMON_BOOST_FREQ_STEP;

		dev_ctrl |= ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;

		if (dev->boost_freq >= tegra->max_freq) {
			dev_ctrl &= ~ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
			dev->boost_freq = tegra->max_freq;
		}
	} else if (intr_status & ACTMON_DEV_INTR_CONSECUTIVE_LOWER) {
		/*
		 * new_boost = old_boost * down_coef
		 * or 0 if (old_boost * down_coef < step / 2)
		 */
		dev->boost_freq = do_percent(dev->boost_freq,
					     dev->config->boost_down_coeff);

		dev_ctrl |= ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;

		if (dev->boost_freq < (ACTMON_BOOST_FREQ_STEP >> 1)) {
			dev_ctrl &= ~ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
			dev->boost_freq = 0;
		}
	}

	device_writel(dev, dev_ctrl, ACTMON_DEV_CTRL);

	device_writel(dev, ACTMON_INTR_STATUS_CLEAR, ACTMON_DEV_INTR_STATUS);
}

static unsigned long actmon_cpu_to_emc_rate(struct tegra_devfreq *tegra,
					    unsigned long cpu_freq)
{
	unsigned int i;
	const struct tegra_actmon_emc_ratio *ratio = actmon_emc_ratios;

	for (i = 0; i < ARRAY_SIZE(actmon_emc_ratios); i++, ratio++) {
		if (cpu_freq >= ratio->cpu_freq) {
			if (ratio->emc_freq >= tegra->max_freq)
				return tegra->max_freq;
			else
				return ratio->emc_freq;
		}
	}

	return 0;
}

static unsigned long actmon_device_target_freq(struct tegra_devfreq *tegra,
					       struct tegra_devfreq_device *dev)
{
	unsigned int avg_sustain_coef;
	unsigned long target_freq;

	target_freq = dev->avg_count / tegra->devfreq->profile->polling_ms;
	avg_sustain_coef = 100 * 100 / dev->config->boost_up_threshold;
	target_freq = do_percent(target_freq, avg_sustain_coef);

	return target_freq;
}

static void actmon_update_target(struct tegra_devfreq *tegra,
				 struct tegra_devfreq_device *dev)
{
	unsigned long cpu_freq = 0;
	unsigned long static_cpu_emc_freq = 0;

	dev->target_freq = actmon_device_target_freq(tegra, dev);

	if (dev->config->avg_dependency_threshold &&
	    dev->config->avg_dependency_threshold <= dev->target_freq) {
		cpu_freq = cpufreq_quick_get(0);
		static_cpu_emc_freq = actmon_cpu_to_emc_rate(tegra, cpu_freq);

		dev->target_freq += dev->boost_freq;
		dev->target_freq = max(dev->target_freq, static_cpu_emc_freq);
	} else {
		dev->target_freq += dev->boost_freq;
	}
}

static irqreturn_t actmon_thread_isr(int irq, void *data)
{
	struct tegra_devfreq *tegra = data;
	bool handled = false;
	unsigned int i;
	u32 val;

	mutex_lock(&tegra->devfreq->lock);

	val = actmon_readl(tegra, ACTMON_GLB_STATUS);
	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
		if (val & tegra->devices[i].config->irq_mask) {
			actmon_isr_device(tegra, tegra->devices + i);
			handled = true;
		}
	}

	if (handled)
		update_devfreq(tegra->devfreq);

	mutex_unlock(&tegra->devfreq->lock);

	return handled ? IRQ_HANDLED : IRQ_NONE;
}

static int tegra_actmon_clk_notify_cb(struct notifier_block *nb,
				      unsigned long action, void *ptr)
{
	struct clk_notifier_data *data = ptr;
	struct tegra_devfreq *tegra;
	struct tegra_devfreq_device *dev;
	unsigned int i;

	if (action != POST_RATE_CHANGE)
		return NOTIFY_OK;

	tegra = container_of(nb, struct tegra_devfreq, clk_rate_change_nb);

	tegra->cur_freq = data->new_rate / KHZ;

	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
		dev = &tegra->devices[i];

		tegra_devfreq_update_wmark(tegra, dev);
	}

	return NOTIFY_OK;
}

static void tegra_actmon_delayed_update(struct work_struct *work)
{
	struct tegra_devfreq *tegra = container_of(work, struct tegra_devfreq,
						   cpufreq_update_work.work);

	mutex_lock(&tegra->devfreq->lock);
	update_devfreq(tegra->devfreq);
	mutex_unlock(&tegra->devfreq->lock);
}

static unsigned long
tegra_actmon_cpufreq_contribution(struct tegra_devfreq *tegra,
				  unsigned int cpu_freq)
{
	struct tegra_devfreq_device *actmon_dev = &tegra->devices[MCCPU];
	unsigned long static_cpu_emc_freq, dev_freq;

	dev_freq = actmon_device_target_freq(tegra, actmon_dev);

	/* check whether CPU's freq is taken into account at all */
	if (dev_freq < actmon_dev->config->avg_dependency_threshold)
		return 0;

	static_cpu_emc_freq = actmon_cpu_to_emc_rate(tegra, cpu_freq);

	if (dev_freq >= static_cpu_emc_freq)
		return 0;

	return static_cpu_emc_freq;
}

static int tegra_actmon_cpu_notify_cb(struct notifier_block *nb,
				      unsigned long action, void *ptr)
{
	struct cpufreq_freqs *freqs = ptr;
	struct tegra_devfreq *tegra;
	unsigned long old, new, delay;

	if (action != CPUFREQ_POSTCHANGE)
		return NOTIFY_OK;

	tegra = container_of(nb, struct tegra_devfreq, cpu_rate_change_nb);

	/*
	 * Quickly check whether CPU frequency should be taken into account
	 * at all, without blocking CPUFreq's core.
	 */
	if (mutex_trylock(&tegra->devfreq->lock)) {
		old = tegra_actmon_cpufreq_contribution(tegra, freqs->old);
		new = tegra_actmon_cpufreq_contribution(tegra, freqs->new);
		mutex_unlock(&tegra->devfreq->lock);

		/*
		 * If CPU's frequency shouldn't be taken into account at
		 * the moment, then there is no need to update the devfreq's
		 * state because ISR will re-check CPU's frequency on the
		 * next interrupt.
		 */
		if (old == new)
			return NOTIFY_OK;
	}

	/*
	 * CPUFreq driver should support CPUFREQ_ASYNC_NOTIFICATION in order
	 * to allow asynchronous notifications. This means we can't block
	 * here for too long, otherwise CPUFreq's core will complain with a
	 * warning splat.
	 */
	delay = msecs_to_jiffies(ACTMON_SAMPLING_PERIOD);
	schedule_delayed_work(&tegra->cpufreq_update_work, delay);

	return NOTIFY_OK;
}

static void tegra_actmon_configure_device(struct tegra_devfreq *tegra,
					  struct tegra_devfreq_device *dev)
{
	u32 val = 0;

	/* reset boosting on governor's restart */
	dev->boost_freq = 0;

	dev->target_freq = tegra->cur_freq;

	dev->avg_count = tegra->cur_freq * tegra->devfreq->profile->polling_ms;
	device_writel(dev, dev->avg_count, ACTMON_DEV_INIT_AVG);

	tegra_devfreq_update_avg_wmark(tegra, dev);
	tegra_devfreq_update_wmark(tegra, dev);

	device_writel(dev, ACTMON_COUNT_WEIGHT, ACTMON_DEV_COUNT_WEIGHT);
	device_writel(dev, ACTMON_INTR_STATUS_CLEAR, ACTMON_DEV_INTR_STATUS);

	val |= ACTMON_DEV_CTRL_ENB_PERIODIC;
	val |= (ACTMON_AVERAGE_WINDOW_LOG2 - 1)
		<< ACTMON_DEV_CTRL_K_VAL_SHIFT;
	val |= (ACTMON_BELOW_WMARK_WINDOW - 1)
		<< ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_NUM_SHIFT;
	val |= (ACTMON_ABOVE_WMARK_WINDOW - 1)
		<< ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_NUM_SHIFT;
	val |= ACTMON_DEV_CTRL_AVG_ABOVE_WMARK_EN;
	val |= ACTMON_DEV_CTRL_AVG_BELOW_WMARK_EN;
	val |= ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
	val |= ACTMON_DEV_CTRL_ENB;

	device_writel(dev, val, ACTMON_DEV_CTRL);
}

static void tegra_actmon_stop_devices(struct tegra_devfreq *tegra)
{
	struct tegra_devfreq_device *dev = tegra->devices;
	unsigned int i;

	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++, dev++) {
		device_writel(dev, ACTMON_DEV_CTRL_STOP, ACTMON_DEV_CTRL);
		device_writel(dev, ACTMON_INTR_STATUS_CLEAR,
			      ACTMON_DEV_INTR_STATUS);
	}
}

static int tegra_actmon_resume(struct tegra_devfreq *tegra)
{
	unsigned int i;
	int err;

	if (!tegra->devfreq->profile->polling_ms || !tegra->started)
		return 0;

	actmon_writel(tegra, tegra->devfreq->profile->polling_ms - 1,
		      ACTMON_GLB_PERIOD_CTRL);

	/*
	 * CLK notifications are needed in order to reconfigure the upper
	 * consecutive watermark in accordance to the actual clock rate
	 * to avoid unnecessary upper interrupts.
	 */
	err = clk_notifier_register(tegra->emc_clock,
				    &tegra->clk_rate_change_nb);
	if (err) {
		dev_err(tegra->devfreq->dev.parent,
			"Failed to register rate change notifier\n");
		return err;
	}

	tegra->cur_freq = clk_get_rate(tegra->emc_clock) / KHZ;

	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
		tegra_actmon_configure_device(tegra, &tegra->devices[i]);

	/*
	 * We are estimating CPU's memory bandwidth requirement based on
	 * amount of memory accesses and system's load, judging by CPU's
	 * frequency. We also don't want to receive events about CPU's
	 * frequency transaction when governor is stopped, hence notifier
	 * is registered dynamically.
	 */
	err = cpufreq_register_notifier(&tegra->cpu_rate_change_nb,
					CPUFREQ_TRANSITION_NOTIFIER);
	if (err) {
		dev_err(tegra->devfreq->dev.parent,
			"Failed to register rate change notifier: %d\n", err);
		goto err_stop;
	}

	enable_irq(tegra->irq);

	return 0;

err_stop:
	tegra_actmon_stop_devices(tegra);

	clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);

	return err;
}

static int tegra_actmon_start(struct tegra_devfreq *tegra)
{
	int ret = 0;

	if (!tegra->started) {
		tegra->started = true;

		ret = tegra_actmon_resume(tegra);
		if (ret)
			tegra->started = false;
	}

	return ret;
}

static void tegra_actmon_pause(struct tegra_devfreq *tegra)
{
	if (!tegra->devfreq->profile->polling_ms || !tegra->started)
		return;

	disable_irq(tegra->irq);

	cpufreq_unregister_notifier(&tegra->cpu_rate_change_nb,
				    CPUFREQ_TRANSITION_NOTIFIER);

	cancel_delayed_work_sync(&tegra->cpufreq_update_work);

	tegra_actmon_stop_devices(tegra);

	clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
}

static void tegra_actmon_stop(struct tegra_devfreq *tegra)
{
	tegra_actmon_pause(tegra);
	tegra->started = false;
}

static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
				u32 flags)
{
	struct tegra_devfreq *tegra = dev_get_drvdata(dev);
	struct devfreq *devfreq = tegra->devfreq;
	struct dev_pm_opp *opp;
	unsigned long rate;
	int err;

	opp = devfreq_recommended_opp(dev, freq, flags);
	if (IS_ERR(opp)) {
		dev_err(dev, "Failed to find opp for %lu Hz\n", *freq);
		return PTR_ERR(opp);
	}
	rate = dev_pm_opp_get_freq(opp);
	dev_pm_opp_put(opp);

	err = clk_set_min_rate(tegra->emc_clock, rate * KHZ);
	if (err)
		return err;

	err = clk_set_rate(tegra->emc_clock, 0);
	if (err)
		goto restore_min_rate;

	return 0;

restore_min_rate:
	clk_set_min_rate(tegra->emc_clock, devfreq->previous_freq);

	return err;
}

static int tegra_devfreq_get_dev_status(struct device *dev,
					struct devfreq_dev_status *stat)
{
	struct tegra_devfreq *tegra = dev_get_drvdata(dev);
	struct tegra_devfreq_device *actmon_dev;
	unsigned long cur_freq;

	cur_freq = READ_ONCE(tegra->cur_freq);

	/* To be used by the tegra governor */
	stat->private_data = tegra;

	/* The below are to be used by the other governors */
	stat->current_frequency = cur_freq;

	actmon_dev = &tegra->devices[MCALL];

	/* Number of cycles spent on memory access */
	stat->busy_time = device_readl(actmon_dev, ACTMON_DEV_AVG_COUNT);

	/* The bus can be considered to be saturated way before 100% */
	stat->busy_time *= 100 / BUS_SATURATION_RATIO;

	/* Number of cycles in a sampling period */
	stat->total_time = tegra->devfreq->profile->polling_ms * cur_freq;

	stat->busy_time = min(stat->busy_time, stat->total_time);

	return 0;
}

static struct devfreq_dev_profile tegra_devfreq_profile = {
	.polling_ms	= ACTMON_SAMPLING_PERIOD,
	.target		= tegra_devfreq_target,
	.get_dev_status	= tegra_devfreq_get_dev_status,
};

static int tegra_governor_get_target(struct devfreq *devfreq,
				     unsigned long *freq)
{
	struct devfreq_dev_status *stat;
	struct tegra_devfreq *tegra;
	struct tegra_devfreq_device *dev;
	unsigned long target_freq = 0;
	unsigned int i;
	int err;

	err = devfreq_update_stats(devfreq);
	if (err)
		return err;

	stat = &devfreq->last_status;

	tegra = stat->private_data;

	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
		dev = &tegra->devices[i];

		actmon_update_target(tegra, dev);

		target_freq = max(target_freq, dev->target_freq);
	}

	*freq = target_freq;

	return 0;
}

static int tegra_governor_event_handler(struct devfreq *devfreq,
					unsigned int event, void *data)
{
	struct tegra_devfreq *tegra = dev_get_drvdata(devfreq->dev.parent);
	unsigned int *new_delay = data;
	int ret = 0;

	/*
	 * Couple devfreq-device with the governor early because it is
	 * needed at the moment of governor's start (used by ISR).
	 */
	tegra->devfreq = devfreq;

	switch (event) {
	case DEVFREQ_GOV_START:
		devfreq_monitor_start(devfreq);
		ret = tegra_actmon_start(tegra);
		break;

	case DEVFREQ_GOV_STOP:
		tegra_actmon_stop(tegra);
		devfreq_monitor_stop(devfreq);
		break;

	case DEVFREQ_GOV_UPDATE_INTERVAL:
		/*
		 * ACTMON hardware supports up to 256 milliseconds for the
		 * sampling period.
		 */
		if (*new_delay > 256) {
			ret = -EINVAL;
			break;
		}

		tegra_actmon_pause(tegra);
		devfreq_update_interval(devfreq, new_delay);
		ret = tegra_actmon_resume(tegra);
		break;

	case DEVFREQ_GOV_SUSPEND:
		tegra_actmon_stop(tegra);
		devfreq_monitor_suspend(devfreq);
		break;

	case DEVFREQ_GOV_RESUME:
		devfreq_monitor_resume(devfreq);
		ret = tegra_actmon_start(tegra);
		break;
	}

	return ret;
}

static struct devfreq_governor tegra_devfreq_governor = {
	.name = "tegra_actmon",
	.get_target_freq = tegra_governor_get_target,
	.event_handler = tegra_governor_event_handler,
	.immutable = true,
	.interrupt_driven = true,
};

static int tegra_devfreq_probe(struct platform_device *pdev)
{
	struct tegra_devfreq_device *dev;
	struct tegra_devfreq *tegra;
	struct devfreq *devfreq;
	unsigned int i;
	long rate;
	int err;

	tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL);
	if (!tegra)
		return -ENOMEM;

	tegra->regs = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(tegra->regs))
		return PTR_ERR(tegra->regs);

	tegra->reset = devm_reset_control_get(&pdev->dev, "actmon");
	if (IS_ERR(tegra->reset)) {
		dev_err(&pdev->dev, "Failed to get reset\n");
		return PTR_ERR(tegra->reset);
	}

	tegra->clock = devm_clk_get(&pdev->dev, "actmon");
	if (IS_ERR(tegra->clock)) {
		dev_err(&pdev->dev, "Failed to get actmon clock\n");
		return PTR_ERR(tegra->clock);
	}

	tegra->emc_clock = devm_clk_get(&pdev->dev, "emc");
	if (IS_ERR(tegra->emc_clock)) {
		dev_err(&pdev->dev, "Failed to get emc clock\n");
		return PTR_ERR(tegra->emc_clock);
	}

	err = platform_get_irq(pdev, 0);
	if (err < 0) {
		dev_err(&pdev->dev, "Failed to get IRQ: %d\n", err);
		return err;
	}
	tegra->irq = err;

	irq_set_status_flags(tegra->irq, IRQ_NOAUTOEN);

	err = devm_request_threaded_irq(&pdev->dev, tegra->irq, NULL,
					actmon_thread_isr, IRQF_ONESHOT,
					"tegra-devfreq", tegra);
	if (err) {
		dev_err(&pdev->dev, "Interrupt request failed: %d\n", err);
		return err;
	}

	reset_control_assert(tegra->reset);

	err = clk_prepare_enable(tegra->clock);
	if (err) {
		dev_err(&pdev->dev,
			"Failed to prepare and enable ACTMON clock\n");
		return err;
	}

	reset_control_deassert(tegra->reset);

	rate = clk_round_rate(tegra->emc_clock, ULONG_MAX);
	if (rate < 0) {
		dev_err(&pdev->dev, "Failed to round clock rate: %ld\n", rate);
		return rate;
	}

	tegra->max_freq = rate / KHZ;

	for (i = 0; i < ARRAY_SIZE(actmon_device_configs); i++) {
		dev = tegra->devices + i;
		dev->config = actmon_device_configs + i;
		dev->regs = tegra->regs + dev->config->offset;
	}

	for (rate = 0; rate <= tegra->max_freq * KHZ; rate++) {
		rate = clk_round_rate(tegra->emc_clock, rate);

		if (rate < 0) {
			dev_err(&pdev->dev,
				"Failed to round clock rate: %ld\n", rate);
			err = rate;
			goto remove_opps;
		}

		err = dev_pm_opp_add(&pdev->dev, rate / KHZ, 0);
		if (err) {
			dev_err(&pdev->dev, "Failed to add OPP: %d\n", err);
			goto remove_opps;
		}
	}

	platform_set_drvdata(pdev, tegra);

	tegra->clk_rate_change_nb.notifier_call = tegra_actmon_clk_notify_cb;
	tegra->cpu_rate_change_nb.notifier_call = tegra_actmon_cpu_notify_cb;

	INIT_DELAYED_WORK(&tegra->cpufreq_update_work,
			  tegra_actmon_delayed_update);

	err = devfreq_add_governor(&tegra_devfreq_governor);
	if (err) {
		dev_err(&pdev->dev, "Failed to add governor: %d\n", err);
		goto remove_opps;
	}

	tegra_devfreq_profile.initial_freq = clk_get_rate(tegra->emc_clock);
	tegra_devfreq_profile.initial_freq /= KHZ;

	devfreq = devfreq_add_device(&pdev->dev, &tegra_devfreq_profile,
				     "tegra_actmon", NULL);
	if (IS_ERR(devfreq)) {
		err = PTR_ERR(devfreq);
		goto remove_governor;
	}

	return 0;

remove_governor:
	devfreq_remove_governor(&tegra_devfreq_governor);

remove_opps:
	dev_pm_opp_remove_all_dynamic(&pdev->dev);

	reset_control_reset(tegra->reset);
	clk_disable_unprepare(tegra->clock);

	return err;
}

static int tegra_devfreq_remove(struct platform_device *pdev)
{
	struct tegra_devfreq *tegra = platform_get_drvdata(pdev);

	devfreq_remove_device(tegra->devfreq);
	devfreq_remove_governor(&tegra_devfreq_governor);

	dev_pm_opp_remove_all_dynamic(&pdev->dev);

	reset_control_reset(tegra->reset);
	clk_disable_unprepare(tegra->clock);

	return 0;
}

static const struct of_device_id tegra_devfreq_of_match[] = {
	{ .compatible = "nvidia,tegra30-actmon" },
	{ .compatible = "nvidia,tegra124-actmon" },
	{ },
};

MODULE_DEVICE_TABLE(of, tegra_devfreq_of_match);

static struct platform_driver tegra_devfreq_driver = {
	.probe	= tegra_devfreq_probe,
	.remove	= tegra_devfreq_remove,
	.driver = {
		.name = "tegra-devfreq",
		.of_match_table = tegra_devfreq_of_match,
	},
};
module_platform_driver(tegra_devfreq_driver);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Tegra devfreq driver");
MODULE_AUTHOR("Tomeu Vizoso <tomeu.vizoso@collabora.com>");