PM / devfreq: exynos: Add generic exynos bus frequency driver

This patch adds the generic exynos bus frequency driver for AMBA AXI bus
of sub-blocks in exynos SoC with DEVFREQ framework. The Samsung Exynos SoC
have the common architecture for bus between DRAM and sub-blocks in SoC.
This driver can support the generic bus frequency driver for Exynos SoCs.

In devicetree, Each bus block has a bus clock, regulator, operation-point
and devfreq-event devices which measure the utilization of each bus block.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
[m.reichl and linux.amoon: Tested it on exynos4412-odroidu3 board]
Tested-by: Markus Reichl <m.reichl@fivetechno.de>
Tested-by: Anand Moon <linux.amoon@gmail.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>

3 files changed, 459 insertions, 0 deletions

diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
index 4de78c552251..cedda8f1e5eb 100644
--- a/drivers/devfreq/Kconfig
+++ b/drivers/devfreq/Kconfig
@@ -66,6 +66,21 @@ config DEVFREQ_GOV_USERSPACE
 
 comment "DEVFREQ Drivers"
 
+config ARM_EXYNOS_BUS_DEVFREQ
+        bool "ARM EXYNOS Generic Memory Bus DEVFREQ Driver"
+        depends on ARCH_EXYNOS
+        select DEVFREQ_GOV_SIMPLE_ONDEMAND
+        select DEVFREQ_EVENT_EXYNOS_PPMU
+        select PM_DEVFREQ_EVENT
+        select PM_OPP
+        help
+          This adds the common DEVFREQ driver for Exynos Memory bus. Exynos
+          Memory bus has one more group of memory bus (e.g, MIF and INT block).
+          Each memory bus group could contain many memoby bus block. It reads
+          PPMU counters of memory controllers by using DEVFREQ-event device
+          and adjusts the operating frequencies and voltages with OPP support.
+          This does not yet operate with optimal voltages.
+
 config ARM_EXYNOS4_BUS_DEVFREQ
         bool "ARM Exynos4210/4212/4412 Memory Bus DEVFREQ Driver"
         depends on (CPU_EXYNOS4210 || SOC_EXYNOS4212 || SOC_EXYNOS4412) && !ARCH_MULTIPLATFORM
diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
index 5134f9ee983d..8af8aaf922a8 100644
--- a/drivers/devfreq/Makefile
+++ b/drivers/devfreq/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
 obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)     += governor_userspace.o
 
 # DEVFREQ Drivers
+obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)    += exynos-bus.o
 obj-$(CONFIG_ARM_EXYNOS4_BUS_DEVFREQ)   += exynos/
 obj-$(CONFIG_ARM_EXYNOS5_BUS_DEVFREQ)   += exynos/
 obj-$(CONFIG_ARM_TEGRA_DEVFREQ)         += tegra-devfreq.o
diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
new file mode 100644
index 000000000000..137de6196af3
--- /dev/null
+++ b/drivers/devfreq/exynos-bus.c
@@ -0,0 +1,443 @@
+/*
+ * Generic Exynos Bus frequency driver with DEVFREQ Framework
+ *
+ * Copyright (c) 2015 Samsung Electronics Co., Ltd.
+ * Author : Chanwoo Choi <cw00.choi@samsung.com>
+ *
+ * This driver support Exynos Bus frequency feature by using
+ * DEVFREQ framework and is based on drivers/devfreq/exynos/exynos4_bus.c.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/devfreq.h>
+#include <linux/devfreq-event.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/pm_opp.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#define DEFAULT_SATURATION_RATIO        40
+#define DEFAULT_VOLTAGE_TOLERANCE       2
+
+struct exynos_bus {
+        struct device *dev;
+
+        struct devfreq *devfreq;
+        struct devfreq_event_dev **edev;
+        unsigned int edev_count;
+        struct mutex lock;
+
+        struct dev_pm_opp *curr_opp;
+
+        struct regulator *regulator;
+        struct clk *clk;
+        unsigned int voltage_tolerance;
+        unsigned int ratio;
+};
+
+/*
+ * Control the devfreq-event device to get the current state of bus
+ */
+#define exynos_bus_ops_edev(ops)                                \
+static int exynos_bus_##ops(struct exynos_bus *bus)             \
+{                                                               \
+        int i, ret;                                             \
+                                                                \
+        for (i = 0; i < bus->edev_count; i++) {                 \
+                if (!bus->edev[i])                              \
+                        continue;                               \
+                ret = devfreq_event_##ops(bus->edev[i]);        \
+                if (ret < 0)                                    \
+                        return ret;                             \
+        }                                                       \
+                                                                \
+        return 0;                                               \
+}
+exynos_bus_ops_edev(enable_edev);
+exynos_bus_ops_edev(disable_edev);
+exynos_bus_ops_edev(set_event);
+
+static int exynos_bus_get_event(struct exynos_bus *bus,
+                                struct devfreq_event_data *edata)
+{
+        struct devfreq_event_data event_data;
+        unsigned long load_count = 0, total_count = 0;
+        int i, ret = 0;
+
+        for (i = 0; i < bus->edev_count; i++) {
+                if (!bus->edev[i])
+                        continue;
+
+                ret = devfreq_event_get_event(bus->edev[i], &event_data);
+                if (ret < 0)
+                        return ret;
+
+                if (i == 0 || event_data.load_count > load_count) {
+                        load_count = event_data.load_count;
+                        total_count = event_data.total_count;
+                }
+        }
+
+        edata->load_count = load_count;
+        edata->total_count = total_count;
+
+        return ret;
+}
+
+/*
+ * Must necessary function for devfreq governor
+ */
+static int exynos_bus_target(struct device *dev, unsigned long *freq, u32 flags)
+{
+        struct exynos_bus *bus = dev_get_drvdata(dev);
+        struct dev_pm_opp *new_opp;
+        unsigned long old_freq, new_freq, old_volt, new_volt, tol;
+        int ret = 0;
+
+        /* Get new opp-bus instance according to new bus clock */
+        rcu_read_lock();
+        new_opp = devfreq_recommended_opp(dev, freq, flags);
+        if (IS_ERR(new_opp)) {
+                dev_err(dev, "failed to get recommended opp instance\n");
+                rcu_read_unlock();
+                return PTR_ERR(new_opp);
+        }
+
+        new_freq = dev_pm_opp_get_freq(new_opp);
+        new_volt = dev_pm_opp_get_voltage(new_opp);
+        old_freq = dev_pm_opp_get_freq(bus->curr_opp);
+        old_volt = dev_pm_opp_get_voltage(bus->curr_opp);
+        rcu_read_unlock();
+
+        if (old_freq == new_freq)
+                return 0;
+        tol = new_volt * bus->voltage_tolerance / 100;
+
+        /* Change voltage and frequency according to new OPP level */
+        mutex_lock(&bus->lock);
+
+        if (old_freq < new_freq) {
+                ret = regulator_set_voltage_tol(bus->regulator, new_volt, tol);
+                if (ret < 0) {
+                        dev_err(bus->dev, "failed to set voltage\n");
+                        goto out;
+                }
+        }
+
+        ret = clk_set_rate(bus->clk, new_freq);
+        if (ret < 0) {
+                dev_err(dev, "failed to change clock of bus\n");
+                clk_set_rate(bus->clk, old_freq);
+                goto out;
+        }
+
+        if (old_freq > new_freq) {
+                ret = regulator_set_voltage_tol(bus->regulator, new_volt, tol);
+                if (ret < 0) {
+                        dev_err(bus->dev, "failed to set voltage\n");
+                        goto out;
+                }
+        }
+        bus->curr_opp = new_opp;
+
+        dev_dbg(dev, "Set the frequency of bus (%lukHz -> %lukHz)\n",
+                        old_freq/1000, new_freq/1000);
+out:
+        mutex_unlock(&bus->lock);
+
+        return ret;
+}
+
+static int exynos_bus_get_dev_status(struct device *dev,
+                                     struct devfreq_dev_status *stat)
+{
+        struct exynos_bus *bus = dev_get_drvdata(dev);
+        struct devfreq_event_data edata;
+        int ret;
+
+        rcu_read_lock();
+        stat->current_frequency = dev_pm_opp_get_freq(bus->curr_opp);
+        rcu_read_unlock();
+
+        ret = exynos_bus_get_event(bus, &edata);
+        if (ret < 0) {
+                stat->total_time = stat->busy_time = 0;
+                goto err;
+        }
+
+        stat->busy_time = (edata.load_count * 100) / bus->ratio;
+        stat->total_time = edata.total_count;
+
+        dev_dbg(dev, "Usage of devfreq-event : %lu/%lu\n", stat->busy_time,
+                                                        stat->total_time);
+
+err:
+        ret = exynos_bus_set_event(bus);
+        if (ret < 0) {
+                dev_err(dev, "failed to set event to devfreq-event devices\n");
+                return ret;
+        }
+
+        return ret;
+}
+
+static void exynos_bus_exit(struct device *dev)
+{
+        struct exynos_bus *bus = dev_get_drvdata(dev);
+        int ret;
+
+        ret = exynos_bus_disable_edev(bus);
+        if (ret < 0)
+                dev_warn(dev, "failed to disable the devfreq-event devices\n");
+
+        if (bus->regulator)
+                regulator_disable(bus->regulator);
+
+        dev_pm_opp_of_remove_table(dev);
+}
+
+static int exynos_bus_parse_of(struct device_node *np,
+                              struct exynos_bus *bus)
+{
+        struct device *dev = bus->dev;
+        unsigned long rate;
+        int i, ret, count, size;
+
+        /* Get the clock to provide each bus with source clock */
+        bus->clk = devm_clk_get(dev, "bus");
+        if (IS_ERR(bus->clk)) {
+                dev_err(dev, "failed to get bus clock\n");
+                return PTR_ERR(bus->clk);
+        }
+
+        ret = clk_prepare_enable(bus->clk);
+        if (ret < 0) {
+                dev_err(dev, "failed to get enable clock\n");
+                return ret;
+        }
+
+        /* Get the freq/voltage OPP table to scale the bus frequency */
+        rcu_read_lock();
+        ret = dev_pm_opp_of_add_table(dev);
+        if (ret < 0) {
+                dev_err(dev, "failed to get OPP table\n");
+                rcu_read_unlock();
+                goto err_clk;
+        }
+
+        rate = clk_get_rate(bus->clk);
+        bus->curr_opp = dev_pm_opp_find_freq_ceil(dev, &rate);
+        if (IS_ERR(bus->curr_opp)) {
+                dev_err(dev, "failed to find dev_pm_opp\n");
+                rcu_read_unlock();
+                ret = PTR_ERR(bus->curr_opp);
+                goto err_opp;
+        }
+        rcu_read_unlock();
+
+        /* Get the regulator to provide each bus with the power */
+        bus->regulator = devm_regulator_get(dev, "vdd");
+        if (IS_ERR(bus->regulator)) {
+                dev_err(dev, "failed to get VDD regulator\n");
+                ret = PTR_ERR(bus->regulator);
+                goto err_opp;
+        }
+
+        ret = regulator_enable(bus->regulator);
+        if (ret < 0) {
+                dev_err(dev, "failed to enable VDD regulator\n");
+                goto err_opp;
+        }
+
+        /*
+         * Get the devfreq-event devices to get the current utilization of
+         * buses. This raw data will be used in devfreq ondemand governor.
+         */
+        count = devfreq_event_get_edev_count(dev);
+        if (count < 0) {
+                dev_err(dev, "failed to get the count of devfreq-event dev\n");
+                ret = count;
+                goto err_regulator;
+        }
+        bus->edev_count = count;
+
+        size = sizeof(*bus->edev) * count;
+        bus->edev = devm_kzalloc(dev, size, GFP_KERNEL);
+        if (!bus->edev) {
+                ret = -ENOMEM;
+                goto err_regulator;
+        }
+
+        for (i = 0; i < count; i++) {
+                bus->edev[i] = devfreq_event_get_edev_by_phandle(dev, i);
+                if (IS_ERR(bus->edev[i])) {
+                        ret = -EPROBE_DEFER;
+                        goto err_regulator;
+                }
+        }
+
+        /*
+         * Optionally, Get the saturation ratio according to Exynos SoC
+         * When measuring the utilization of each AXI bus with devfreq-event
+         * devices, the measured real cycle might be much lower than the
+         * total cycle of bus during sampling rate. In result, the devfreq
+         * simple-ondemand governor might not decide to change the current
+         * frequency due to too utilization (= real cycle/total cycle).
+         * So, this property is used to adjust the utilization when calculating
+         * the busy_time in exynos_bus_get_dev_status().
+         */
+        if (of_property_read_u32(np, "exynos,saturation-ratio", &bus->ratio))
+                bus->ratio = DEFAULT_SATURATION_RATIO;
+
+        if (of_property_read_u32(np, "exynos,voltage-tolerance",
+                                        &bus->voltage_tolerance))
+                bus->voltage_tolerance = DEFAULT_VOLTAGE_TOLERANCE;
+
+        return 0;
+
+err_regulator:
+        regulator_disable(bus->regulator);
+err_opp:
+        dev_pm_opp_of_remove_table(dev);
+err_clk:
+        clk_disable_unprepare(bus->clk);
+
+        return ret;
+}
+
+static int exynos_bus_probe(struct platform_device *pdev)
+{
+        struct device *dev = &pdev->dev;
+        struct device_node *np = dev->of_node;
+        struct devfreq_dev_profile *profile;
+        struct devfreq_simple_ondemand_data *ondemand_data;
+        struct exynos_bus *bus;
+        int ret;
+
+        if (!np) {
+                dev_err(dev, "failed to find devicetree node\n");
+                return -EINVAL;
+        }
+
+        bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
+        if (!bus)
+                return -ENOMEM;
+        mutex_init(&bus->lock);
+        bus->dev = &pdev->dev;
+        platform_set_drvdata(pdev, bus);
+
+        /* Parse the device-tree to get the resource information */
+        ret = exynos_bus_parse_of(np, bus);
+        if (ret < 0)
+                return ret;
+
+        /* Initalize the struct profile and governor data */
+        profile = devm_kzalloc(dev, sizeof(*profile), GFP_KERNEL);
+        if (!profile)
+                return -ENOMEM;
+        profile->polling_ms = 50;
+        profile->target = exynos_bus_target;
+        profile->get_dev_status = exynos_bus_get_dev_status;
+        profile->exit = exynos_bus_exit;
+
+        ondemand_data = devm_kzalloc(dev, sizeof(*ondemand_data), GFP_KERNEL);
+        if (!ondemand_data)
+                return -ENOMEM;
+        ondemand_data->upthreshold = 40;
+        ondemand_data->downdifferential = 5;
+
+        /* Add devfreq device to monitor and handle the exynos bus */
+        bus->devfreq = devm_devfreq_add_device(dev, profile, "simple_ondemand",
+                                                ondemand_data);
+        if (IS_ERR(bus->devfreq)) {
+                dev_err(dev, "failed to add devfreq device\n");
+                return  PTR_ERR(bus->devfreq);
+        }
+
+        /* Register opp_notifier to catch the change of OPP  */
+        ret = devm_devfreq_register_opp_notifier(dev, bus->devfreq);
+        if (ret < 0) {
+                dev_err(dev, "failed to register opp notifier\n");
+                return ret;
+        }
+
+        /*
+         * Enable devfreq-event to get raw data which is used to determine
+         * current bus load.
+         */
+        ret = exynos_bus_enable_edev(bus);
+        if (ret < 0) {
+                dev_err(dev, "failed to enable devfreq-event devices\n");
+                return ret;
+        }
+
+        ret = exynos_bus_set_event(bus);
+        if (ret < 0) {
+                dev_err(dev, "failed to set event to devfreq-event devices\n");
+                return ret;
+        }
+
+        return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int exynos_bus_resume(struct device *dev)
+{
+        struct exynos_bus *bus = dev_get_drvdata(dev);
+        int ret;
+
+        ret = exynos_bus_enable_edev(bus);
+        if (ret < 0) {
+                dev_err(dev, "failed to enable the devfreq-event devices\n");
+                return ret;
+        }
+
+        return 0;
+}
+
+static int exynos_bus_suspend(struct device *dev)
+{
+        struct exynos_bus *bus = dev_get_drvdata(dev);
+        int ret;
+
+        ret = exynos_bus_disable_edev(bus);
+        if (ret < 0) {
+                dev_err(dev, "failed to disable the devfreq-event devices\n");
+                return ret;
+        }
+
+        return 0;
+}
+#endif
+
+static const struct dev_pm_ops exynos_bus_pm = {
+        SET_SYSTEM_SLEEP_PM_OPS(exynos_bus_suspend, exynos_bus_resume)
+};
+
+static const struct of_device_id exynos_bus_of_match[] = {
+        { .compatible = "samsung,exynos-bus", },
+        { /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, exynos_bus_of_match);
+
+static struct platform_driver exynos_bus_platdrv = {
+        .probe          = exynos_bus_probe,
+        .driver = {
+                .name   = "exynos-bus",
+                .pm     = &exynos_bus_pm,
+                .of_match_table = of_match_ptr(exynos_bus_of_match),
+        },
+};
+module_platform_driver(exynos_bus_platdrv);
+
+MODULE_DESCRIPTION("Generic Exynos Bus frequency driver");
+MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
+MODULE_LICENSE("GPL v2");