PM / devfreq: tegra: add devfreq driver for Tegra Activity Monitor

The ACTMON block can monitor several counters, providing averaging and firing
interrupts based on watermarking configuration. This implementation monitors
the MCALL and MCCPU counters to choose an appropriate frequency for the
external memory clock.

This patch is based on work by Alex Frid <afrid@nvidia.com> and Mikko
Perttunen <mikko.perttunen@kapsi.fi>.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

1 files changed, 718 insertions, 0 deletions

diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
new file mode 100644
index 000000000000..34790961af5a
--- /dev/null
+++ b/drivers/devfreq/tegra-devfreq.c
@@ -0,0 +1,718 @@
+/*
+ * A devfreq driver for NVIDIA Tegra SoCs
+ *
+ * Copyright (c) 2014 NVIDIA CORPORATION. All rights reserved.
+ * Copyright (C) 2014 Google, Inc
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/cpufreq.h>
+#include <linux/devfreq.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+#include <linux/reset.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_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
+
+/* 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 in %
+ */
+struct tegra_devfreq_device_config {
+        u32             offset;
+        u32             irq_mask;
+
+        unsigned int    boost_up_coeff;
+        unsigned int    boost_down_coeff;
+        unsigned int    boost_up_threshold;
+        unsigned int    boost_down_threshold;
+        u32             avg_dependency_threshold;
+};
+
+enum tegra_actmon_device {
+        MCALL = 0,
+        MCCPU,
+};
+
+static struct tegra_devfreq_device_config actmon_device_configs[] = {
+        {
+                /* MCALL */
+                .offset = 0x1c0,
+                .irq_mask = 1 << 26,
+                .boost_up_coeff = 200,
+                .boost_down_coeff = 50,
+                .boost_up_threshold = 60,
+                .boost_down_threshold = 40,
+        },
+        {
+                /* MCCPU */
+                .offset = 0x200,
+                .irq_mask = 1 << 25,
+                .boost_up_coeff = 800,
+                .boost_down_coeff = 90,
+                .boost_up_threshold = 27,
+                .boost_down_threshold = 10,
+                .avg_dependency_threshold = 50000,
+        },
+};
+
+/**
+ * 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;
+        u32             avg_band_freq;
+        u32             avg_count;
+
+        unsigned long   target_freq;
+        unsigned long   boost_freq;
+};
+
+struct tegra_devfreq {
+        struct devfreq          *devfreq;
+
+        struct platform_device  *pdev;
+        struct reset_control    *reset;
+        struct clk              *clock;
+        void __iomem            *regs;
+
+        spinlock_t              lock;
+
+        struct clk              *emc_clock;
+        unsigned long           max_freq;
+        unsigned long           cur_freq;
+        struct notifier_block   rate_change_nb;
+
+        struct tegra_devfreq_device devices[ARRAY_SIZE(actmon_device_configs)];
+};
+
+struct tegra_actmon_emc_ratio {
+        unsigned long cpu_freq;
+        unsigned long emc_freq;
+};
+
+static struct tegra_actmon_emc_ratio actmon_emc_ratios[] = {
+        { 1400000, ULONG_MAX },
+        { 1200000,    750000 },
+        { 1100000,    600000 },
+        { 1000000,    500000 },
+        {  800000,    375000 },
+        {  500000,    200000 },
+        {  250000,    100000 },
+};
+
+static unsigned long do_percent(unsigned long val, unsigned int pct)
+{
+        return val * pct / 100;
+}
+
+static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq_device *dev)
+{
+        u32 avg = dev->avg_count;
+        u32 band = dev->avg_band_freq * ACTMON_SAMPLING_PERIOD;
+
+        writel(avg + band, dev->regs + ACTMON_DEV_AVG_UPPER_WMARK);
+        avg = max(avg, band);
+        writel(avg - band, dev->regs + 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 * ACTMON_SAMPLING_PERIOD;
+
+        writel(do_percent(val, dev->config->boost_up_threshold),
+               dev->regs + ACTMON_DEV_UPPER_WMARK);
+
+        writel(do_percent(val, dev->config->boost_down_threshold),
+               dev->regs + ACTMON_DEV_LOWER_WMARK);
+}
+
+static void actmon_write_barrier(struct tegra_devfreq *tegra)
+{
+        /* ensure the update has reached the ACTMON */
+        wmb();
+        readl(tegra->regs + ACTMON_GLB_STATUS);
+}
+
+static irqreturn_t actmon_isr(int irq, void *data)
+{
+        struct tegra_devfreq *tegra = data;
+        struct tegra_devfreq_device *dev = NULL;
+        unsigned long flags;
+        u32 val;
+        unsigned int i;
+
+        val = readl(tegra->regs + ACTMON_GLB_STATUS);
+
+        for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
+                if (val & tegra->devices[i].config->irq_mask) {
+                        dev = tegra->devices + i;
+                        break;
+                }
+        }
+
+        if (!dev)
+                return IRQ_NONE;
+
+        spin_lock_irqsave(&tegra->lock, flags);
+
+        dev->avg_count = readl(dev->regs + ACTMON_DEV_AVG_COUNT);
+        tegra_devfreq_update_avg_wmark(dev);
+
+        val = readl(dev->regs + ACTMON_DEV_INTR_STATUS);
+        if (val & ACTMON_DEV_INTR_CONSECUTIVE_UPPER) {
+                val = readl(dev->regs + ACTMON_DEV_CTRL) |
+                        ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN |
+                        ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
+
+                /*
+                 * 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;
+                if (dev->boost_freq >= tegra->max_freq) {
+                        dev->boost_freq = tegra->max_freq;
+                        val &= ~ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
+                }
+                writel(val, dev->regs + ACTMON_DEV_CTRL);
+        } else if (val & ACTMON_DEV_INTR_CONSECUTIVE_LOWER) {
+                val = readl(dev->regs + ACTMON_DEV_CTRL) |
+                        ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN |
+                        ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
+
+                /*
+                 * 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);
+                if (dev->boost_freq < (ACTMON_BOOST_FREQ_STEP >> 1)) {
+                        dev->boost_freq = 0;
+                        val &= ~ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
+                }
+                writel(val, dev->regs + ACTMON_DEV_CTRL);
+        }
+
+        if (dev->config->avg_dependency_threshold) {
+                val = readl(dev->regs + ACTMON_DEV_CTRL);
+                if (dev->avg_count >= dev->config->avg_dependency_threshold)
+                        val |= ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
+                else if (dev->boost_freq == 0)
+                        val &= ~ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
+                writel(val, dev->regs + ACTMON_DEV_CTRL);
+        }
+
+        writel(ACTMON_INTR_STATUS_CLEAR, dev->regs + ACTMON_DEV_INTR_STATUS);
+
+        actmon_write_barrier(tegra);
+
+        spin_unlock_irqrestore(&tegra->lock, flags);
+
+        return IRQ_WAKE_THREAD;
+}
+
+static unsigned long actmon_cpu_to_emc_rate(struct tegra_devfreq *tegra,
+                                            unsigned long cpu_freq)
+{
+        unsigned int i;
+        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 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;
+        unsigned int avg_sustain_coef;
+        unsigned long flags;
+
+        if (dev->config->avg_dependency_threshold) {
+                cpu_freq = cpufreq_get(0);
+                static_cpu_emc_freq = actmon_cpu_to_emc_rate(tegra, cpu_freq);
+        }
+
+        spin_lock_irqsave(&tegra->lock, flags);
+
+        dev->target_freq = dev->avg_count / ACTMON_SAMPLING_PERIOD;
+        avg_sustain_coef = 100 * 100 / dev->config->boost_up_threshold;
+        dev->target_freq = do_percent(dev->target_freq, avg_sustain_coef);
+        dev->target_freq += dev->boost_freq;
+
+        if (dev->avg_count >= dev->config->avg_dependency_threshold)
+                dev->target_freq = max(dev->target_freq, static_cpu_emc_freq);
+
+        spin_unlock_irqrestore(&tegra->lock, flags);
+}
+
+static irqreturn_t actmon_thread_isr(int irq, void *data)
+{
+        struct tegra_devfreq *tegra = data;
+
+        mutex_lock(&tegra->devfreq->lock);
+        update_devfreq(tegra->devfreq);
+        mutex_unlock(&tegra->devfreq->lock);
+
+        return IRQ_HANDLED;
+}
+
+static int tegra_actmon_rate_notify_cb(struct notifier_block *nb,
+                                       unsigned long action, void *ptr)
+{
+        struct clk_notifier_data *data = ptr;
+        struct tegra_devfreq *tegra = container_of(nb, struct tegra_devfreq,
+                                                   rate_change_nb);
+        unsigned int i;
+        unsigned long flags;
+
+        spin_lock_irqsave(&tegra->lock, flags);
+
+        switch (action) {
+        case POST_RATE_CHANGE:
+                tegra->cur_freq = data->new_rate / KHZ;
+
+                for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
+                        tegra_devfreq_update_wmark(tegra, tegra->devices + i);
+
+                actmon_write_barrier(tegra);
+                break;
+        case PRE_RATE_CHANGE:
+                /* fall through */
+        case ABORT_RATE_CHANGE:
+                break;
+        };
+
+        spin_unlock_irqrestore(&tegra->lock, flags);
+
+        return NOTIFY_OK;
+}
+
+static void tegra_actmon_configure_device(struct tegra_devfreq *tegra,
+                                          struct tegra_devfreq_device *dev)
+{
+        u32 val;
+
+        dev->avg_band_freq = tegra->max_freq * ACTMON_DEFAULT_AVG_BAND / KHZ;
+        dev->target_freq = tegra->cur_freq;
+
+        dev->avg_count = tegra->cur_freq * ACTMON_SAMPLING_PERIOD;
+        writel(dev->avg_count, dev->regs + ACTMON_DEV_INIT_AVG);
+
+        tegra_devfreq_update_avg_wmark(dev);
+        tegra_devfreq_update_wmark(tegra, dev);
+
+        writel(ACTMON_COUNT_WEIGHT, dev->regs + ACTMON_DEV_COUNT_WEIGHT);
+        writel(ACTMON_INTR_STATUS_CLEAR, dev->regs + ACTMON_DEV_INTR_STATUS);
+
+        val = 0;
+        val |= ACTMON_DEV_CTRL_ENB_PERIODIC |
+               ACTMON_DEV_CTRL_AVG_ABOVE_WMARK_EN |
+               ACTMON_DEV_CTRL_AVG_BELOW_WMARK_EN;
+        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_CONSECUTIVE_BELOW_WMARK_EN |
+               ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
+
+        writel(val, dev->regs + ACTMON_DEV_CTRL);
+
+        actmon_write_barrier(tegra);
+
+        val = readl(dev->regs + ACTMON_DEV_CTRL);
+        val |= ACTMON_DEV_CTRL_ENB;
+        writel(val, dev->regs + ACTMON_DEV_CTRL);
+
+        actmon_write_barrier(tegra);
+}
+
+static int tegra_devfreq_suspend(struct device *dev)
+{
+        struct platform_device *pdev;
+        struct tegra_devfreq *tegra;
+        struct tegra_devfreq_device *actmon_dev;
+        unsigned int i;
+        u32 val;
+
+        pdev = container_of(dev, struct platform_device, dev);
+        tegra = platform_get_drvdata(pdev);
+
+        for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
+                actmon_dev = &tegra->devices[i];
+
+                val = readl(actmon_dev->regs + ACTMON_DEV_CTRL);
+                val &= ~ACTMON_DEV_CTRL_ENB;
+                writel(val, actmon_dev->regs + ACTMON_DEV_CTRL);
+
+                writel(ACTMON_INTR_STATUS_CLEAR,
+                       actmon_dev->regs + ACTMON_DEV_INTR_STATUS);
+
+                actmon_write_barrier(tegra);
+        }
+
+        return 0;
+}
+
+static int tegra_devfreq_resume(struct device *dev)
+{
+        struct platform_device *pdev;
+        struct tegra_devfreq *tegra;
+        struct tegra_devfreq_device *actmon_dev;
+        unsigned int i;
+
+        pdev = container_of(dev, struct platform_device, dev);
+        tegra = platform_get_drvdata(pdev);
+
+        for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
+                actmon_dev = &tegra->devices[i];
+
+                tegra_actmon_configure_device(tegra, actmon_dev);
+        }
+
+        return 0;
+}
+
+static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
+                                u32 flags)
+{
+        struct platform_device *pdev;
+        struct tegra_devfreq *tegra;
+        struct dev_pm_opp *opp;
+        unsigned long rate = *freq * KHZ;
+
+        pdev = container_of(dev, struct platform_device, dev);
+        tegra = platform_get_drvdata(pdev);
+
+        rcu_read_lock();
+        opp = devfreq_recommended_opp(dev, &rate, flags);
+        if (IS_ERR(opp)) {
+                rcu_read_unlock();
+                dev_err(dev, "Failed to find opp for %lu KHz\n", *freq);
+                return PTR_ERR(opp);
+        }
+        rate = dev_pm_opp_get_freq(opp);
+        rcu_read_unlock();
+
+        /* TODO: Once we have per-user clk constraints, set a floor */
+        clk_set_rate(tegra->emc_clock, rate);
+
+        /* TODO: Set voltage as well */
+
+        return 0;
+}
+
+static int tegra_devfreq_get_dev_status(struct device *dev,
+                                        struct devfreq_dev_status *stat)
+{
+        struct platform_device *pdev;
+        struct tegra_devfreq *tegra;
+        struct tegra_devfreq_device *actmon_dev;
+
+        pdev = container_of(dev, struct platform_device, dev);
+        tegra = platform_get_drvdata(pdev);
+
+        stat->current_frequency = tegra->cur_freq;
+
+        /* To be used by the tegra governor */
+        stat->private_data = tegra;
+
+        /* The below are to be used by the other governors */
+
+        actmon_dev = &tegra->devices[MCALL];
+
+        /* Number of cycles spent on memory access */
+        stat->busy_time = 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 = ACTMON_SAMPLING_PERIOD * tegra->cur_freq;
+
+        return 0;
+}
+
+static int tegra_devfreq_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->profile->get_dev_status(devfreq->dev.parent, &stat);
+        if (err)
+                return err;
+
+        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_devfreq_event_handler(struct devfreq *devfreq,
+                                       unsigned int event, void *data)
+{
+        return 0;
+}
+
+static struct devfreq_governor tegra_devfreq_governor = {
+        .name = "tegra",
+        .get_target_freq = tegra_devfreq_get_target,
+        .event_handler = tegra_devfreq_event_handler,
+};
+
+static struct devfreq_dev_profile tegra_devfreq_profile = {
+        .polling_ms     = 0,
+        .target         = tegra_devfreq_target,
+        .get_dev_status = tegra_devfreq_get_dev_status,
+};
+
+static int tegra_devfreq_probe(struct platform_device *pdev)
+{
+        struct tegra_devfreq *tegra;
+        struct tegra_devfreq_device *dev;
+        struct resource *res;
+        unsigned long max_freq;
+        unsigned int i;
+        int irq;
+        int err;
+
+        tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL);
+        if (!tegra)
+                return -ENOMEM;
+
+        spin_lock_init(&tegra->lock);
+
+        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        if (!res) {
+                dev_err(&pdev->dev, "Failed to get regs resource\n");
+                return -ENODEV;
+        }
+
+        tegra->regs = devm_ioremap_resource(&pdev->dev, res);
+        if (IS_ERR(tegra->regs)) {
+                dev_err(&pdev->dev, "Failed to get IO memory\n");
+                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 = of_init_opp_table(&pdev->dev);
+        if (err) {
+                dev_err(&pdev->dev, "Failed to init operating point table\n");
+                return err;
+        }
+
+        tegra->rate_change_nb.notifier_call = tegra_actmon_rate_notify_cb;
+        err = clk_notifier_register(tegra->emc_clock, &tegra->rate_change_nb);
+        if (err) {
+                dev_err(&pdev->dev,
+                        "Failed to register rate change notifier\n");
+                return err;
+        }
+
+        reset_control_assert(tegra->reset);
+
+        err = clk_prepare_enable(tegra->clock);
+        if (err) {
+                reset_control_deassert(tegra->reset);
+                return err;
+        }
+
+        reset_control_deassert(tegra->reset);
+
+        max_freq = clk_round_rate(tegra->emc_clock, ULONG_MAX);
+        tegra->max_freq = max_freq / KHZ;
+
+        clk_set_rate(tegra->emc_clock, max_freq);
+
+        tegra->cur_freq = clk_get_rate(tegra->emc_clock) / KHZ;
+
+        writel(ACTMON_SAMPLING_PERIOD - 1,
+               tegra->regs + ACTMON_GLB_PERIOD_CTRL);
+
+        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;
+
+                tegra_actmon_configure_device(tegra, tegra->devices + i);
+        }
+
+        err = devfreq_add_governor(&tegra_devfreq_governor);
+        if (err) {
+                dev_err(&pdev->dev, "Failed to add governor\n");
+                return err;
+        }
+
+        tegra_devfreq_profile.initial_freq = clk_get_rate(tegra->emc_clock);
+        tegra->devfreq = devm_devfreq_add_device(&pdev->dev,
+                                                 &tegra_devfreq_profile,
+                                                 "tegra",
+                                                 NULL);
+
+        irq = platform_get_irq(pdev, 0);
+        err = devm_request_threaded_irq(&pdev->dev, irq, actmon_isr,
+                                        actmon_thread_isr, IRQF_SHARED,
+                                        "tegra-devfreq", tegra);
+        if (err) {
+                dev_err(&pdev->dev, "Interrupt request failed\n");
+                return err;
+        }
+
+        platform_set_drvdata(pdev, tegra);
+
+        return 0;
+}
+
+static int tegra_devfreq_remove(struct platform_device *pdev)
+{
+        struct tegra_devfreq *tegra = platform_get_drvdata(pdev);
+
+        clk_notifier_unregister(tegra->emc_clock, &tegra->rate_change_nb);
+
+        clk_disable_unprepare(tegra->clock);
+
+        return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(tegra_devfreq_pm_ops,
+                         tegra_devfreq_suspend,
+                         tegra_devfreq_resume);
+
+static struct of_device_id tegra_devfreq_of_match[] = {
+        { .compatible = "nvidia,tegra124-actmon" },
+        { },
+};
+
+static struct platform_driver tegra_devfreq_driver = {
+        .probe  = tegra_devfreq_probe,
+        .remove = tegra_devfreq_remove,
+        .driver = {
+                .name           = "tegra-devfreq",
+                .owner          = THIS_MODULE,
+                .of_match_table = tegra_devfreq_of_match,
+                .pm             = &tegra_devfreq_pm_ops,
+        },
+};
+module_platform_driver(tegra_devfreq_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Tegra devfreq driver");
+MODULE_AUTHOR("Tomeu Vizoso <tomeu.vizoso@collabora.com>");
+MODULE_DEVICE_TABLE(of, tegra_devfreq_of_match);