drivers/devfreq/governor_cpubw_hwmon.c

/*
 * 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) "cpubw-hwmon: " fmt

#include <linux/kernel.h>
#include <asm/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 <mach/msm-krait-l2-accessors.h>

#define L2PMRESR2		0x412
#define L2PMCR			0x400
#define L2PMCNTENCLR		0x402
#define L2PMCNTENSET		0x403
#define L2PMINTENCLR		0x404
#define L2PMINTENSET		0x405
#define L2PMOVSR		0x406
#define L2PMOVSSET		0x407
#define L2PMnEVCNTCR(n)		(0x420 + n * 0x10)
#define L2PMnEVCNTR(n)		(0x421 + n * 0x10)
#define L2PMnEVCNTSR(n)		(0x422 + n * 0x10)
#define L2PMnEVFILTER(n)	(0x423 + n * 0x10)
#define L2PMnEVTYPER(n)		(0x424 + n * 0x10)

#define show_attr(name) \
static ssize_t show_##name(struct device *dev,				\
			struct device_attribute *attr, char *buf)	\
{									\
	return sprintf(buf, "%u\n", 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)					\
{									\
	int ret;							\
	unsigned int val;						\
	ret = sscanf(buf, "%u", &val);					\
	if (ret != 1)							\
		return -EINVAL;						\
	val = max(val, _min);				\
	val = min(val, _max);				\
	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)


static int l2pm_irq;
static unsigned int bytes_per_beat;
static unsigned int tolerance_percent = 10;
static unsigned int guard_band_mbps = 100;
static unsigned int decay_rate = 90;
static unsigned int io_percent = 16;
static unsigned int bw_step = 190;

#define MIN_MS	10U
#define MAX_MS	500U
static unsigned int sample_ms = 50;
static u32 prev_r_start_val;
static u32 prev_w_start_val;
static unsigned long prev_ab;
static ktime_t prev_ts;

#define RD_MON	0
#define WR_MON	1
static void mon_init(void)
{
	/* Set up counters 0/1 to count write/read beats */
	set_l2_indirect_reg(L2PMRESR2, 0x8B0B0000);
	set_l2_indirect_reg(L2PMnEVCNTCR(RD_MON), 0x0);
	set_l2_indirect_reg(L2PMnEVCNTCR(WR_MON), 0x0);
	set_l2_indirect_reg(L2PMnEVCNTR(RD_MON), 0xFFFFFFFF);
	set_l2_indirect_reg(L2PMnEVCNTR(WR_MON), 0xFFFFFFFF);
	set_l2_indirect_reg(L2PMnEVFILTER(RD_MON), 0xF003F);
	set_l2_indirect_reg(L2PMnEVFILTER(WR_MON), 0xF003F);
	set_l2_indirect_reg(L2PMnEVTYPER(RD_MON), 0xA);
	set_l2_indirect_reg(L2PMnEVTYPER(WR_MON), 0xB);
}

static void global_mon_enable(bool en)
{
	u32 regval;

	/* Global counter enable */
	regval = get_l2_indirect_reg(L2PMCR);
	if (en)
		regval |= BIT(0);
	else
		regval &= ~BIT(0);
	set_l2_indirect_reg(L2PMCR, regval);
}

static void mon_enable(int n)
{
	/* Clear previous overflow state for event counter n */
	set_l2_indirect_reg(L2PMOVSR, BIT(n));

	/* Enable event counter n */
	set_l2_indirect_reg(L2PMCNTENSET, BIT(n));
}

static void mon_disable(int n)
{
	/* Disable event counter n */
	set_l2_indirect_reg(L2PMCNTENCLR, BIT(n));
}

static void mon_irq_enable(int n, bool en)
{
	if (en)
		set_l2_indirect_reg(L2PMINTENSET, BIT(n));
	else
		set_l2_indirect_reg(L2PMINTENCLR, BIT(n));
}

/* Returns start counter value to be used with mon_get_mbps() */
static u32 mon_set_limit_mbyte(int n, unsigned int mbytes)
{
	u32 regval, beats;

	beats = mult_frac(mbytes, SZ_1M, bytes_per_beat);
	regval = 0xFFFFFFFF - beats;
	set_l2_indirect_reg(L2PMnEVCNTR(n), regval);
	pr_debug("EV%d MB: %d, start val: %x\n", n, mbytes, regval);

	return regval;
}

long mon_get_count(int n, u32 start_val)
{
	u32 overflow, count;

	count = get_l2_indirect_reg(L2PMnEVCNTR(n));
	overflow = get_l2_indirect_reg(L2PMOVSR);

	pr_debug("EV%d ov: %x, cnt: %x\n", n, overflow, count);

	if (overflow & BIT(n))
		return 0xFFFFFFFF - start_val + count;
	else
		return count - start_val;
}

/* Returns MBps of read/writes for the sampling window. */
unsigned int beats_to_mbps(long long beats, unsigned int us)
{
	beats *= USEC_PER_SEC;
	beats *= bytes_per_beat;
	do_div(beats, us);
	beats = DIV_ROUND_UP_ULL(beats, SZ_1M);

	return beats;
}

static int to_limit(int mbps)
{
	mbps *= (100 + tolerance_percent) * sample_ms;
	mbps /= 100;
	mbps = DIV_ROUND_UP(mbps, MSEC_PER_SEC);
	return mbps;
}

unsigned long measure_bw_and_set_irq(void)
{
	long r_mbps, w_mbps, mbps;
	ktime_t ts;
	unsigned int us;

	/*
	 * 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, prev_ts));
	if (!us)
		us = 1;

	mon_disable(RD_MON);
	mon_disable(WR_MON);

	r_mbps = mon_get_count(RD_MON, prev_r_start_val);
	r_mbps = beats_to_mbps(r_mbps, us);
	w_mbps = mon_get_count(WR_MON, prev_w_start_val);
	w_mbps = beats_to_mbps(w_mbps, us);

	prev_r_start_val = mon_set_limit_mbyte(RD_MON, to_limit(r_mbps));
	prev_w_start_val = mon_set_limit_mbyte(WR_MON, to_limit(w_mbps));
	prev_ts = ts;

	mon_enable(RD_MON);
	mon_enable(WR_MON);

	preempt_enable();

	mbps = r_mbps + w_mbps;
	pr_debug("R/W/BW/us = %ld/%ld/%ld/%d\n", r_mbps, w_mbps, mbps, us);

	return mbps;
}

static void compute_bw(int mbps, unsigned long *freq, unsigned long *ab)
{
	int new_bw;

	mbps += guard_band_mbps;

	if (mbps > prev_ab) {
		new_bw = mbps;
	} else {
		new_bw = mbps * decay_rate + prev_ab * (100 - decay_rate);
		new_bw /= 100;
	}

	*ab = roundup(mbps, bw_step);
	*freq = (mbps * 100) / io_percent;
}

#define TOO_SOON_US	(1 * USEC_PER_MSEC)
static irqreturn_t mon_intr_handler(int irq, void *dev)
{
	struct devfreq *df = dev;
	ktime_t ts;
	unsigned int us;
	u32 regval;
	int ret;

	regval = get_l2_indirect_reg(L2PMOVSR);
	pr_debug("Got interrupt: %x\n", regval);

	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, prev_ts));
	if (us > TOO_SOON_US) {
		mutex_lock(&df->lock);
		ret = update_devfreq(df);
		if (ret)
			pr_err("Unable to update freq on IRQ!\n");
		mutex_unlock(&df->lock);
	}

	devfreq_monitor_start(df);

	return IRQ_HANDLED;
}

static int start_monitoring(struct devfreq *df)
{
	int ret, mbyte;

	ret = request_threaded_irq(l2pm_irq, NULL, mon_intr_handler,
			  IRQF_ONESHOT | IRQF_SHARED,
			  "cpubw_hwmon", df);
	if (ret) {
		pr_err("Unable to register interrupt handler\n");
		return ret;
	}

	mon_init();
	mon_disable(RD_MON);
	mon_disable(WR_MON);

	mbyte = (df->previous_freq * io_percent) / (2 * 100);
	prev_r_start_val = mon_set_limit_mbyte(RD_MON, mbyte);
	prev_w_start_val = mon_set_limit_mbyte(WR_MON, mbyte);
	prev_ts = ktime_get();
	prev_ab = 0;

	mon_irq_enable(RD_MON, true);
	mon_irq_enable(WR_MON, true);
	mon_enable(RD_MON);
	mon_enable(WR_MON);
	global_mon_enable(true);

	return 0;
}

static void stop_monitoring(struct devfreq *df)
{
	global_mon_enable(false);
	mon_disable(RD_MON);
	mon_disable(WR_MON);
	mon_irq_enable(RD_MON, false);
	mon_irq_enable(WR_MON, false);

	disable_irq(l2pm_irq);
	free_irq(l2pm_irq, df);
}

static int devfreq_cpubw_hwmon_get_freq(struct devfreq *df,
					unsigned long *freq,
					u32 *flag)
{
	unsigned long mbps;

	mbps = measure_bw_and_set_irq();
	compute_bw(mbps, freq, df->data);
	prev_ab = *(unsigned long *) df->data;

	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 = "cpubw_hwmon",
	.attrs = dev_attr,
};

static int devfreq_cpubw_hwmon_ev_handler(struct devfreq *df,
					unsigned int event, void *data)
{
	int ret;

	switch (event) {
	case DEVFREQ_GOV_START:
		ret = start_monitoring(df);
		if (ret)
			return ret;
		ret = sysfs_create_group(&df->dev.kobj, &dev_attr_group);
		if (ret)
			return ret;

		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;
		devfreq_monitor_start(df);

		pr_debug("Enabled CPU BW HW monitor governor\n");
		break;

	case DEVFREQ_GOV_STOP:
		sysfs_remove_group(&df->dev.kobj, &dev_attr_group);
		devfreq_monitor_stop(df);
		*(unsigned long *)df->data = 0;
		stop_monitoring(df);
		pr_debug("Disabled CPU 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_cpubw_hwmon = {
	.name = "cpubw_hwmon",
	.get_target_freq = devfreq_cpubw_hwmon_get_freq,
	.event_handler = devfreq_cpubw_hwmon_ev_handler,
};

static int cpubw_hwmon_driver_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	int ret;

	l2pm_irq = platform_get_irq(pdev, 0);
	if (l2pm_irq < 0) {
		pr_err("Unable to get IRQ number\n");
		return l2pm_irq;
	}

	ret = of_property_read_u32(dev->of_node, "qcom,bytes-per-beat",
			     &bytes_per_beat);
	if (ret) {
		pr_err("Unable to read bytes per beat\n");
		return ret;
	}

	ret = devfreq_add_governor(&devfreq_cpubw_hwmon);
	if (ret) {
		pr_err("devfreq governor registration failed\n");
		return ret;
	}

	return 0;
}

static struct of_device_id match_table[] = {
	{ .compatible = "qcom,kraitbw-l2pm" },
	{}
};

static struct platform_driver cpubw_hwmon_driver = {
	.probe = cpubw_hwmon_driver_probe,
	.driver = {
		.name = "kraitbw-l2pm",
		.of_match_table = match_table,
		.owner = THIS_MODULE,
	},
};

static int __init cpubw_hwmon_init(void)
{
	return platform_driver_register(&cpubw_hwmon_driver);
}
module_init(cpubw_hwmon_init);

static void __exit cpubw_hwmon_exit(void)
{
	platform_driver_unregister(&cpubw_hwmon_driver);
}
module_exit(cpubw_hwmon_exit);

MODULE_DESCRIPTION("HW monitor based CPU DDR bandwidth voting driver");
MODULE_LICENSE("GPL v2");