PM / devfreq: Generic bandwidth hw monitor

This is a snapshot of the Generic bandwidth hw monitor driver as of
msm-3.10 commit:

acdce027751d5a7488b283f0ce3111f873a5816d (Merge "defconfig: arm64:
Enable ONESHOT_SYNC for msm8994")

Signed-off-by: Kumar Gala <galak@codeaurora.org>

drivers/devfreq/Kconfig

@@ -80,6 +80,18 @@ config DEVFREQ_GOV_CPUFREQ
 	  CPU frequency to device frequency mapping table(s). This governor
 	  can be useful for controlling devices such as DDR, cache, CCI, etc.
 
+config DEVFREQ_GOV_MSM_BW_HWMON
+	tristate "HW monitor based governor for device BW"
+	depends on ARCH_MSM_KRAIT || ARCH_MSM_BIMC_BWMON
+	help
+	  HW monitor based governor for device to DDR bandwidth voting.
+
+	  When this governor is used for Krait CPUs, it sets the Krait CPU BW
+	  vote by using L2 PM counters to monitor the Krait's use of DDR.
+	  Since this uses some of the Krait PM counters it can conflict with
+	  existing profiling tools.  This governor is unlikely to be useful
+	  for non-MSM devices.
+
 config DEVFREQ_GOV_MSM_CACHE_HWMON
 	tristate "HW monitor based governor for cache frequency"
 	help

drivers/devfreq/Makefile

@@ -7,6 +7,7 @@ obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
 obj-$(CONFIG_DEVFREQ_GOV_QCOM_ADRENO_TZ) += governor_msm_adreno_tz.o
 obj-$(CONFIG_DEVFREQ_GOV_CPUFREQ)	+= governor_cpufreq.o
 obj-$(CONFIG_ARCH_MSM_KRAIT)		+= krait-l2pm.o
+obj-$(CONFIG_DEVFREQ_GOV_MSM_BW_HWMON)	+= governor_bw_hwmon.o
 obj-$(CONFIG_DEVFREQ_GOV_MSM_CACHE_HWMON)	+= governor_cache_hwmon.o
 
 # DEVFREQ Drivers

drivers/devfreq/governor_bw_hwmon.c

@@ -0,0 +1,433 @@
+/*
+ * Copyright (c) 2013-2014, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that 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.
+ */
+
+#define pr_fmt(fmt) "bw-hwmon: " fmt
+
+#include <linux/kernel.h>
+#include <linux/sizes.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/delay.h>
+#include <linux/ktime.h>
+#include <linux/time.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/mutex.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/devfreq.h>
+#include "governor.h"
+#include "governor_bw_hwmon.h"
+
+struct hwmon_node {
+	unsigned int tolerance_percent;
+	unsigned int guard_band_mbps;
+	unsigned int decay_rate;
+	unsigned int io_percent;
+	unsigned int bw_step;
+	unsigned long prev_ab;
+	unsigned long *dev_ab;
+	ktime_t prev_ts;
+	bool mon_started;
+	struct list_head list;
+	void *orig_data;
+	struct bw_hwmon *hw;
+	struct devfreq_governor *gov;
+	struct attribute_group *attr_grp;
+};
+
+static LIST_HEAD(hwmon_list);
+static DEFINE_MUTEX(list_lock);
+
+static int use_cnt;
+static DEFINE_MUTEX(state_lock);
+
+#define show_attr(name) \
+static ssize_t show_##name(struct device *dev,				\
+			struct device_attribute *attr, char *buf)	\
+{									\
+	struct devfreq *df = to_devfreq(dev);				\
+	struct hwmon_node *hw = df->data;				\
+	return snprintf(buf, PAGE_SIZE, "%u\n", hw->name);		\
+}
+
+#define store_attr(name, _min, _max) \
+static ssize_t store_##name(struct device *dev,				\
+			struct device_attribute *attr, const char *buf,	\
+			size_t count)					\
+{									\
+	struct devfreq *df = to_devfreq(dev);				\
+	struct hwmon_node *hw = df->data;				\
+	int ret;							\
+	unsigned int val;						\
+	ret = sscanf(buf, "%u", &val);					\
+	if (ret != 1)							\
+		return -EINVAL;						\
+	val = max(val, _min);						\
+	val = min(val, _max);						\
+	hw->name = val;							\
+	return count;							\
+}
+
+#define gov_attr(__attr, min, max)	\
+show_attr(__attr)			\
+store_attr(__attr, min, max)		\
+static DEVICE_ATTR(__attr, 0644, show_##__attr, store_##__attr)
+
+#define MIN_MS	10U
+#define MAX_MS	500U
+
+static unsigned long measure_bw_and_set_irq(struct hwmon_node *node)
+{
+	ktime_t ts;
+	unsigned int us;
+	unsigned long mbps;
+	struct bw_hwmon *hw = node->hw;
+
+	/*
+	 * Since we are stopping the counters, we don't want this short work
+	 * to be interrupted by other tasks and cause the measurements to be
+	 * wrong. Not blocking interrupts to avoid affecting interrupt
+	 * latency and since they should be short anyway because they run in
+	 * atomic context.
+	 */
+	preempt_disable();
+
+	ts = ktime_get();
+	us = ktime_to_us(ktime_sub(ts, node->prev_ts));
+	if (!us)
+		us = 1;
+
+	mbps = hw->meas_bw_and_set_irq(hw, node->tolerance_percent, us);
+	node->prev_ts = ts;
+
+	preempt_enable();
+
+	dev_dbg(hw->df->dev.parent, "BW MBps = %6lu, period = %u\n", mbps, us);
+
+	return mbps;
+}
+
+static void compute_bw(struct hwmon_node *node, int mbps,
+			unsigned long *freq, unsigned long *ab)
+{
+	int new_bw;
+
+	mbps += node->guard_band_mbps;
+
+	if (mbps > node->prev_ab) {
+		new_bw = mbps;
+	} else {
+		new_bw = mbps * node->decay_rate
+			+ node->prev_ab * (100 - node->decay_rate);
+		new_bw /= 100;
+	}
+
+	node->prev_ab = new_bw;
+	if (ab)
+		*ab = roundup(new_bw, node->bw_step);
+	*freq = (new_bw * 100) / node->io_percent;
+}
+
+static struct hwmon_node *find_hwmon_node(struct devfreq *df)
+{
+	struct hwmon_node *node, *found = NULL;
+
+	mutex_lock(&list_lock);
+	list_for_each_entry(node, &hwmon_list, list)
+		if (node->hw->dev == df->dev.parent ||
+		    node->hw->of_node == df->dev.parent->of_node ||
+		    (!node->hw->dev && !node->hw->of_node &&
+		     node->gov == df->governor)) {
+			found = node;
+			break;
+		}
+	mutex_unlock(&list_lock);
+
+	return found;
+}
+
+#define TOO_SOON_US	(1 * USEC_PER_MSEC)
+int update_bw_hwmon(struct bw_hwmon *hwmon)
+{
+	struct devfreq *df;
+	struct hwmon_node *node;
+	ktime_t ts;
+	unsigned int us;
+	int ret;
+
+	if (!hwmon)
+		return -EINVAL;
+	df = hwmon->df;
+	if (!df)
+		return -ENODEV;
+	node = find_hwmon_node(df);
+	if (!node)
+		return -ENODEV;
+
+	if (!node->mon_started)
+		return -EBUSY;
+
+	dev_dbg(df->dev.parent, "Got update request\n");
+	devfreq_monitor_stop(df);
+
+	/*
+	 * Don't recalc bandwidth if the interrupt comes right after a
+	 * previous bandwidth calculation.  This is done for two reasons:
+	 *
+	 * 1. Sampling the BW during a very short duration can result in a
+	 *    very inaccurate measurement due to very short bursts.
+	 * 2. This can only happen if the limit was hit very close to the end
+	 *    of the previous sample period. Which means the current BW
+	 *    estimate is not very off and doesn't need to be readjusted.
+	 */
+	ts = ktime_get();
+	us = ktime_to_us(ktime_sub(ts, node->prev_ts));
+	if (us > TOO_SOON_US) {
+		mutex_lock(&df->lock);
+		ret = update_devfreq(df);
+		if (ret)
+			dev_err(df->dev.parent,
+				"Unable to update freq on request!\n");
+		mutex_unlock(&df->lock);
+	}
+
+	devfreq_monitor_start(df);
+
+	return 0;
+}
+
+static int start_monitoring(struct devfreq *df)
+{
+	int ret = 0;
+	unsigned long mbps;
+	struct device *dev = df->dev.parent;
+	struct hwmon_node *node;
+	struct bw_hwmon *hw;
+	struct devfreq_dev_status stat;
+
+	node = find_hwmon_node(df);
+	if (!node) {
+		dev_err(dev, "Unable to find HW monitor!\n");
+		return -ENODEV;
+	}
+	hw = node->hw;
+
+	stat.private_data = NULL;
+	if (df->profile->get_dev_status)
+		ret = df->profile->get_dev_status(df->dev.parent, &stat);
+	if (ret || !stat.private_data)
+		dev_warn(dev, "Device doesn't take AB votes!\n");
+	else
+		node->dev_ab = stat.private_data;
+
+	hw->df = df;
+	node->orig_data = df->data;
+	df->data = node;
+
+	node->prev_ts = ktime_get();
+	node->prev_ab = 0;
+	mbps = (df->previous_freq * node->io_percent) / 100;
+	ret = hw->start_hwmon(hw, mbps);
+	if (ret) {
+		dev_err(dev, "Unable to start HW monitor!\n");
+		goto err_start;
+	}
+
+	devfreq_monitor_start(df);
+	node->mon_started = true;
+
+	ret = sysfs_create_group(&df->dev.kobj, node->attr_grp);
+	if (ret)
+		goto err_sysfs;
+
+	return 0;
+
+err_sysfs:
+	node->mon_started = false;
+	devfreq_monitor_stop(df);
+	hw->stop_hwmon(hw);
+err_start:
+	df->data = node->orig_data;
+	node->orig_data = NULL;
+	hw->df = NULL;
+	node->dev_ab = NULL;
+	return ret;
+}
+
+static void stop_monitoring(struct devfreq *df)
+{
+	struct hwmon_node *node = df->data;
+	struct bw_hwmon *hw = node->hw;
+
+	sysfs_remove_group(&df->dev.kobj, node->attr_grp);
+	node->mon_started = false;
+	devfreq_monitor_stop(df);
+	hw->stop_hwmon(hw);
+	df->data = node->orig_data;
+	node->orig_data = NULL;
+	hw->df = NULL;
+	/*
+	 * Not all governors know about this additional extended device
+	 * configuration. To avoid leaving the extended configuration at a
+	 * stale state, set it to 0 and let the next governor take it from
+	 * there.
+	 */
+	if (node->dev_ab)
+		*node->dev_ab = 0;
+	node->dev_ab = NULL;
+}
+
+static int devfreq_bw_hwmon_get_freq(struct devfreq *df,
+					unsigned long *freq,
+					u32 *flag)
+{
+	unsigned long mbps;
+	struct hwmon_node *node = df->data;
+
+	mbps = measure_bw_and_set_irq(node);
+	compute_bw(node, mbps, freq, node->dev_ab);
+
+	return 0;
+}
+
+gov_attr(tolerance_percent, 0U, 30U);
+gov_attr(guard_band_mbps, 0U, 2000U);
+gov_attr(decay_rate, 0U, 100U);
+gov_attr(io_percent, 1U, 100U);
+gov_attr(bw_step, 50U, 1000U);
+
+static struct attribute *dev_attr[] = {
+	&dev_attr_tolerance_percent.attr,
+	&dev_attr_guard_band_mbps.attr,
+	&dev_attr_decay_rate.attr,
+	&dev_attr_io_percent.attr,
+	&dev_attr_bw_step.attr,
+	NULL,
+};
+
+static struct attribute_group dev_attr_group = {
+	.name = "bw_hwmon",
+	.attrs = dev_attr,
+};
+
+static int devfreq_bw_hwmon_ev_handler(struct devfreq *df,
+					unsigned int event, void *data)
+{
+	int ret;
+	unsigned int sample_ms;
+
+	switch (event) {
+	case DEVFREQ_GOV_START:
+		sample_ms = df->profile->polling_ms;
+		sample_ms = max(MIN_MS, sample_ms);
+		sample_ms = min(MAX_MS, sample_ms);
+		df->profile->polling_ms = sample_ms;
+
+		ret = start_monitoring(df);
+		if (ret)
+			return ret;
+
+		dev_dbg(df->dev.parent,
+			"Enabled dev BW HW monitor governor\n");
+		break;
+
+	case DEVFREQ_GOV_STOP:
+		stop_monitoring(df);
+		dev_dbg(df->dev.parent,
+			"Disabled dev BW HW monitor governor\n");
+		break;
+
+	case DEVFREQ_GOV_INTERVAL:
+		sample_ms = *(unsigned int *)data;
+		sample_ms = max(MIN_MS, sample_ms);
+		sample_ms = min(MAX_MS, sample_ms);
+		devfreq_interval_update(df, &sample_ms);
+		break;
+	}
+
+	return 0;
+}
+
+static struct devfreq_governor devfreq_gov_bw_hwmon = {
+	.name = "bw_hwmon",
+	.get_target_freq = devfreq_bw_hwmon_get_freq,
+	.event_handler = devfreq_bw_hwmon_ev_handler,
+};
+
+int register_bw_hwmon(struct device *dev, struct bw_hwmon *hwmon)
+{
+	int ret = 0;
+	struct hwmon_node *node;
+	struct attribute_group *attr_grp;
+
+	if (!hwmon->gov && !hwmon->dev && !hwmon->of_node)
+		return -EINVAL;
+
+	node = devm_kzalloc(dev, sizeof(*node), GFP_KERNEL);
+	if (!node) {
+		dev_err(dev, "Unable to register gov. Out of memory!\n");
+		return -ENOMEM;
+	}
+
+	if (hwmon->gov) {
+		attr_grp = devm_kzalloc(dev, sizeof(*attr_grp), GFP_KERNEL);
+		if (!attr_grp)
+			return -ENOMEM;
+
+		hwmon->gov->get_target_freq = devfreq_bw_hwmon_get_freq;
+		hwmon->gov->event_handler = devfreq_bw_hwmon_ev_handler;
+		attr_grp->name = hwmon->gov->name;
+		attr_grp->attrs = dev_attr;
+
+		node->gov = hwmon->gov;
+		node->attr_grp = attr_grp;
+	} else {
+		node->gov = &devfreq_gov_bw_hwmon;
+		node->attr_grp = &dev_attr_group;
+	}
+
+	node->tolerance_percent = 10;
+	node->guard_band_mbps = 100;
+	node->decay_rate = 90;
+	node->io_percent = 16;
+	node->bw_step = 190;
+	node->hw = hwmon;
+
+	mutex_lock(&list_lock);
+	list_add_tail(&node->list, &hwmon_list);
+	mutex_unlock(&list_lock);
+
+	if (hwmon->gov) {
+		ret = devfreq_add_governor(hwmon->gov);
+	} else {
+		mutex_lock(&state_lock);
+		if (!use_cnt)
+			ret = devfreq_add_governor(&devfreq_gov_bw_hwmon);
+		if (!ret)
+			use_cnt++;
+		mutex_unlock(&state_lock);
+	}
+
+	if (!ret)
+		dev_info(dev, "BW HWmon governor registered.\n");
+	else
+		dev_err(dev, "BW HWmon governor registration failed!\n");
+
+	return ret;
+}
+
+MODULE_DESCRIPTION("HW monitor based dev DDR bandwidth voting driver");
+MODULE_LICENSE("GPL v2");

drivers/devfreq/governor_bw_hwmon.h

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that 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.
+ */
+
+#ifndef _GOVERNOR_BW_HWMON_H
+#define _GOVERNOR_BW_HWMON_H
+
+#include <linux/kernel.h>
+#include <linux/devfreq.h>
+
+/**
+ * struct bw_hwmon - dev BW HW monitor info
+ * @start_hwmon:		Start the HW monitoring of the dev BW
+ * @stop_hwmon:			Stop the HW monitoring of dev BW
+ * @is_valid_irq:		Check whether the IRQ was triggered by the
+ *				counters used to monitor dev BW.
+ * @meas_bw_and_set_irq:	Return the measured bandwidth and set up the
+ *				IRQ to fire if the usage exceeds current
+ *				measurement by @tol percent.
+ * @irq:			IRQ number that corresponds to this HW
+ *				monitor.
+ * @dev:			Pointer to device that this HW monitor can
+ *				monitor.
+ * @of_node:			OF node of device that this HW monitor can
+ *				monitor.
+ * @gov:			devfreq_governor struct that should be used
+ *				when registering this HW monitor with devfreq.
+ *				Only the name field is expected to be
+ *				initialized.
+ * @df:				Devfreq node that this HW monitor is being
+ *				used for. NULL when not actively in use and
+ *				non-NULL when in use.
+ *
+ * One of dev, of_node or governor_name needs to be specified for a
+ * successful registration.
+ *
+ */
+struct bw_hwmon {
+	int (*start_hwmon)(struct bw_hwmon *hw, unsigned long mbps);
+	void (*stop_hwmon)(struct bw_hwmon *hw);
+	unsigned long (*meas_bw_and_set_irq)(struct bw_hwmon *hw,
+					unsigned int tol, unsigned int us);
+	struct device *dev;
+	struct device_node *of_node;
+	struct devfreq_governor *gov;
+
+	struct devfreq *df;
+};
+
+#ifdef CONFIG_DEVFREQ_GOV_MSM_BW_HWMON
+int register_bw_hwmon(struct device *dev, struct bw_hwmon *hwmon);
+int update_bw_hwmon(struct bw_hwmon *hwmon);
+#else
+static inline int register_bw_hwmon(struct device *dev,
+					struct bw_hwmon *hwmon)
+{
+	return 0;
+}
+int update_bw_hwmon(struct bw_hwmon *hwmon)
+{
+	return 0;
+}
+#endif
+
+#endif /* _GOVERNOR_BW_HWMON_H */