// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2014-2018, The Linux Foundation. All rights reserved.
 * Copyright (C) 2021-2022 Linaro Ltd
 * Author: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>, based on
 *         previous work of Thara Gopinath and msm-4.9 downstream sources.
 */
#include <linux/interconnect.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
#include <linux/sizes.h>

/*
 * The BWMON samples data throughput within 'sample_ms' time. With three
 * configurable thresholds (Low, Medium and High) gives four windows (called
 * zones) of current bandwidth:
 *
 * Zone 0: byte count < THRES_LO
 * Zone 1: THRES_LO < byte count < THRES_MED
 * Zone 2: THRES_MED < byte count < THRES_HIGH
 * Zone 3: THRES_HIGH < byte count
 *
 * Zones 0 and 2 are not used by this driver.
 */

/* Internal sampling clock frequency */
#define HW_TIMER_HZ				19200000

#define BWMON_GLOBAL_IRQ_STATUS			0x0
#define BWMON_GLOBAL_IRQ_CLEAR			0x8
#define BWMON_GLOBAL_IRQ_ENABLE			0xc
#define BWMON_GLOBAL_IRQ_ENABLE_ENABLE		BIT(0)

#define BWMON_IRQ_STATUS			0x100
#define BWMON_IRQ_STATUS_ZONE_SHIFT		4
#define BWMON_IRQ_CLEAR				0x108
#define BWMON_IRQ_ENABLE			0x10c
#define BWMON_IRQ_ENABLE_ZONE1_SHIFT		5
#define BWMON_IRQ_ENABLE_ZONE2_SHIFT		6
#define BWMON_IRQ_ENABLE_ZONE3_SHIFT		7
#define BWMON_IRQ_ENABLE_MASK			(BIT(BWMON_IRQ_ENABLE_ZONE1_SHIFT) | \
						 BIT(BWMON_IRQ_ENABLE_ZONE3_SHIFT))

#define BWMON_ENABLE				0x2a0
#define BWMON_ENABLE_ENABLE			BIT(0)

#define BWMON_CLEAR				0x2a4
#define BWMON_CLEAR_CLEAR			BIT(0)

#define BWMON_SAMPLE_WINDOW			0x2a8
#define BWMON_THRESHOLD_HIGH			0x2ac
#define BWMON_THRESHOLD_MED			0x2b0
#define BWMON_THRESHOLD_LOW			0x2b4

#define BWMON_ZONE_ACTIONS			0x2b8
/*
 * Actions to perform on some zone 'z' when current zone hits the threshold:
 * Increment counter of zone 'z'
 */
#define BWMON_ZONE_ACTIONS_INCREMENT(z)		(0x2 << ((z) * 2))
/* Clear counter of zone 'z' */
#define BWMON_ZONE_ACTIONS_CLEAR(z)		(0x1 << ((z) * 2))

/* Zone 0 threshold hit: Clear zone count */
#define BWMON_ZONE_ACTIONS_ZONE0		(BWMON_ZONE_ACTIONS_CLEAR(0))

/* Zone 1 threshold hit: Increment zone count & clear lower zones */
#define BWMON_ZONE_ACTIONS_ZONE1		(BWMON_ZONE_ACTIONS_INCREMENT(1) | \
						 BWMON_ZONE_ACTIONS_CLEAR(0))

/* Zone 2 threshold hit: Increment zone count & clear lower zones */
#define BWMON_ZONE_ACTIONS_ZONE2		(BWMON_ZONE_ACTIONS_INCREMENT(2) | \
						 BWMON_ZONE_ACTIONS_CLEAR(1) | \
						 BWMON_ZONE_ACTIONS_CLEAR(0))

/* Zone 3 threshold hit: Increment zone count & clear lower zones */
#define BWMON_ZONE_ACTIONS_ZONE3		(BWMON_ZONE_ACTIONS_INCREMENT(3) | \
						 BWMON_ZONE_ACTIONS_CLEAR(2) | \
						 BWMON_ZONE_ACTIONS_CLEAR(1) | \
						 BWMON_ZONE_ACTIONS_CLEAR(0))
/* Value for BWMON_ZONE_ACTIONS */
#define BWMON_ZONE_ACTIONS_DEFAULT		(BWMON_ZONE_ACTIONS_ZONE0 | \
						 BWMON_ZONE_ACTIONS_ZONE1 << 8 | \
						 BWMON_ZONE_ACTIONS_ZONE2 << 16 | \
						 BWMON_ZONE_ACTIONS_ZONE3 << 24)

/*
 * There is no clear documentation/explanation of BWMON_THRESHOLD_COUNT
 * register. Based on observations, this is number of times one threshold has to
 * be reached, to trigger interrupt in given zone.
 *
 * 0xff are maximum values meant to ignore the zones 0 and 2.
 */
#define BWMON_THRESHOLD_COUNT			0x2bc
#define BWMON_THRESHOLD_COUNT_ZONE1_SHIFT	8
#define BWMON_THRESHOLD_COUNT_ZONE2_SHIFT	16
#define BWMON_THRESHOLD_COUNT_ZONE3_SHIFT	24
#define BWMON_THRESHOLD_COUNT_ZONE0_DEFAULT	0xff
#define BWMON_THRESHOLD_COUNT_ZONE2_DEFAULT	0xff

/* BWMONv4 count registers use count unit of 64 kB */
#define BWMON_COUNT_UNIT_KB			64
#define BWMON_ZONE_COUNT			0x2d8
#define BWMON_ZONE_MAX(zone)			(0x2e0 + 4 * (zone))

struct icc_bwmon_data {
	unsigned int sample_ms;
	unsigned int default_highbw_kbps;
	unsigned int default_medbw_kbps;
	unsigned int default_lowbw_kbps;
	u8 zone1_thres_count;
	u8 zone3_thres_count;
};

struct icc_bwmon {
	struct device *dev;
	void __iomem *base;
	int irq;

	unsigned int default_lowbw_kbps;
	unsigned int sample_ms;
	unsigned int max_bw_kbps;
	unsigned int min_bw_kbps;
	unsigned int target_kbps;
	unsigned int current_kbps;
};

static void bwmon_clear_counters(struct icc_bwmon *bwmon)
{
	/*
	 * Clear counters. The order and barriers are
	 * important. Quoting downstream Qualcomm msm-4.9 tree:
	 *
	 * The counter clear and IRQ clear bits are not in the same 4KB
	 * region. So, we need to make sure the counter clear is completed
	 * before we try to clear the IRQ or do any other counter operations.
	 */
	writel(BWMON_CLEAR_CLEAR, bwmon->base + BWMON_CLEAR);
}

static void bwmon_clear_irq(struct icc_bwmon *bwmon)
{
	/*
	 * Clear zone and global interrupts. The order and barriers are
	 * important. Quoting downstream Qualcomm msm-4.9 tree:
	 *
	 * Synchronize the local interrupt clear in mon_irq_clear()
	 * with the global interrupt clear here. Otherwise, the CPU
	 * may reorder the two writes and clear the global interrupt
	 * before the local interrupt, causing the global interrupt
	 * to be retriggered by the local interrupt still being high.
	 *
	 * Similarly, because the global registers are in a different
	 * region than the local registers, we need to ensure any register
	 * writes to enable the monitor after this call are ordered with the
	 * clearing here so that local writes don't happen before the
	 * interrupt is cleared.
	 */
	writel(BWMON_IRQ_ENABLE_MASK, bwmon->base + BWMON_IRQ_CLEAR);
	writel(BIT(0), bwmon->base + BWMON_GLOBAL_IRQ_CLEAR);
}

static void bwmon_disable(struct icc_bwmon *bwmon)
{
	/* Disable interrupts. Strict ordering, see bwmon_clear_irq(). */
	writel(0x0, bwmon->base + BWMON_GLOBAL_IRQ_ENABLE);
	writel(0x0, bwmon->base + BWMON_IRQ_ENABLE);

	/*
	 * Disable bwmon. Must happen before bwmon_clear_irq() to avoid spurious
	 * IRQ.
	 */
	writel(0x0, bwmon->base + BWMON_ENABLE);
}

static void bwmon_enable(struct icc_bwmon *bwmon, unsigned int irq_enable)
{
	/* Enable interrupts */
	writel(BWMON_GLOBAL_IRQ_ENABLE_ENABLE,
	       bwmon->base + BWMON_GLOBAL_IRQ_ENABLE);
	writel(irq_enable, bwmon->base + BWMON_IRQ_ENABLE);

	/* Enable bwmon */
	writel(BWMON_ENABLE_ENABLE, bwmon->base + BWMON_ENABLE);
}

static unsigned int bwmon_kbps_to_count(unsigned int kbps)
{
	return kbps / BWMON_COUNT_UNIT_KB;
}

static void bwmon_set_threshold(struct icc_bwmon *bwmon, unsigned int reg,
				unsigned int kbps)
{
	unsigned int thres;

	thres = mult_frac(bwmon_kbps_to_count(kbps), bwmon->sample_ms,
			  MSEC_PER_SEC);
	writel_relaxed(thres, bwmon->base + reg);
}

static void bwmon_start(struct icc_bwmon *bwmon,
			const struct icc_bwmon_data *data)
{
	unsigned int thres_count;
	int window;

	bwmon_clear_counters(bwmon);

	window = mult_frac(bwmon->sample_ms, HW_TIMER_HZ, MSEC_PER_SEC);
	/* Maximum sampling window: 0xfffff */
	writel_relaxed(window, bwmon->base + BWMON_SAMPLE_WINDOW);

	bwmon_set_threshold(bwmon, BWMON_THRESHOLD_HIGH,
			    data->default_highbw_kbps);
	bwmon_set_threshold(bwmon, BWMON_THRESHOLD_MED,
			    data->default_medbw_kbps);
	bwmon_set_threshold(bwmon, BWMON_THRESHOLD_LOW,
			    data->default_lowbw_kbps);

	thres_count = data->zone3_thres_count << BWMON_THRESHOLD_COUNT_ZONE3_SHIFT |
		      BWMON_THRESHOLD_COUNT_ZONE2_DEFAULT << BWMON_THRESHOLD_COUNT_ZONE2_SHIFT |
		      data->zone1_thres_count << BWMON_THRESHOLD_COUNT_ZONE1_SHIFT |
		      BWMON_THRESHOLD_COUNT_ZONE0_DEFAULT;
	writel_relaxed(thres_count, bwmon->base + BWMON_THRESHOLD_COUNT);
	writel_relaxed(BWMON_ZONE_ACTIONS_DEFAULT,
		       bwmon->base + BWMON_ZONE_ACTIONS);
	/* Write barriers in bwmon_clear_irq() */

	bwmon_clear_irq(bwmon);
	bwmon_enable(bwmon, BWMON_IRQ_ENABLE_MASK);
}

static irqreturn_t bwmon_intr(int irq, void *dev_id)
{
	struct icc_bwmon *bwmon = dev_id;
	unsigned int status, max;
	int zone;

	status = readl(bwmon->base + BWMON_IRQ_STATUS);
	status &= BWMON_IRQ_ENABLE_MASK;
	if (!status) {
		/*
		 * Only zone 1 and zone 3 interrupts are enabled but zone 2
		 * threshold could be hit and trigger interrupt even if not
		 * enabled.
		 * Such spurious interrupt might come with valuable max count or
		 * not, so solution would be to always check all
		 * BWMON_ZONE_MAX() registers to find the highest value.
		 * Such case is currently ignored.
		 */
		return IRQ_NONE;
	}

	bwmon_disable(bwmon);

	zone = get_bitmask_order(status >> BWMON_IRQ_STATUS_ZONE_SHIFT) - 1;
	/*
	 * Zone max bytes count register returns count units within sampling
	 * window.  Downstream kernel for BWMONv4 (called BWMON type 2 in
	 * downstream) always increments the max bytes count by one.
	 */
	max = readl(bwmon->base + BWMON_ZONE_MAX(zone)) + 1;
	max *= BWMON_COUNT_UNIT_KB;
	bwmon->target_kbps = mult_frac(max, MSEC_PER_SEC, bwmon->sample_ms);

	return IRQ_WAKE_THREAD;
}

static irqreturn_t bwmon_intr_thread(int irq, void *dev_id)
{
	struct icc_bwmon *bwmon = dev_id;
	unsigned int irq_enable = 0;
	struct dev_pm_opp *opp, *target_opp;
	unsigned int bw_kbps, up_kbps, down_kbps;

	bw_kbps = bwmon->target_kbps;

	target_opp = dev_pm_opp_find_bw_ceil(bwmon->dev, &bw_kbps, 0);
	if (IS_ERR(target_opp) && PTR_ERR(target_opp) == -ERANGE)
		target_opp = dev_pm_opp_find_bw_floor(bwmon->dev, &bw_kbps, 0);

	bwmon->target_kbps = bw_kbps;

	bw_kbps--;
	opp = dev_pm_opp_find_bw_floor(bwmon->dev, &bw_kbps, 0);
	if (IS_ERR(opp) && PTR_ERR(opp) == -ERANGE)
		down_kbps = bwmon->target_kbps;
	else
		down_kbps = bw_kbps;

	up_kbps = bwmon->target_kbps + 1;

	if (bwmon->target_kbps >= bwmon->max_bw_kbps)
		irq_enable = BIT(BWMON_IRQ_ENABLE_ZONE1_SHIFT);
	else if (bwmon->target_kbps <= bwmon->min_bw_kbps)
		irq_enable = BIT(BWMON_IRQ_ENABLE_ZONE3_SHIFT);
	else
		irq_enable = BWMON_IRQ_ENABLE_MASK;

	bwmon_set_threshold(bwmon, BWMON_THRESHOLD_HIGH, up_kbps);
	bwmon_set_threshold(bwmon, BWMON_THRESHOLD_MED, down_kbps);
	/* Write barriers in bwmon_clear_counters() */
	bwmon_clear_counters(bwmon);
	bwmon_clear_irq(bwmon);
	bwmon_enable(bwmon, irq_enable);

	if (bwmon->target_kbps == bwmon->current_kbps)
		goto out;

	dev_pm_opp_set_opp(bwmon->dev, target_opp);
	bwmon->current_kbps = bwmon->target_kbps;

out:
	dev_pm_opp_put(target_opp);
	if (!IS_ERR(opp))
		dev_pm_opp_put(opp);

	return IRQ_HANDLED;
}

static int bwmon_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct dev_pm_opp *opp;
	struct icc_bwmon *bwmon;
	const struct icc_bwmon_data *data;
	int ret;

	bwmon = devm_kzalloc(dev, sizeof(*bwmon), GFP_KERNEL);
	if (!bwmon)
		return -ENOMEM;

	data = of_device_get_match_data(dev);

	bwmon->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(bwmon->base)) {
		dev_err(dev, "failed to map bwmon registers\n");
		return PTR_ERR(bwmon->base);
	}

	bwmon->irq = platform_get_irq(pdev, 0);
	if (bwmon->irq < 0)
		return bwmon->irq;

	ret = devm_pm_opp_of_add_table(dev);
	if (ret)
		return dev_err_probe(dev, ret, "failed to add OPP table\n");

	bwmon->max_bw_kbps = UINT_MAX;
	opp = dev_pm_opp_find_bw_floor(dev, &bwmon->max_bw_kbps, 0);
	if (IS_ERR(opp))
		return dev_err_probe(dev, ret, "failed to find max peak bandwidth\n");

	bwmon->min_bw_kbps = 0;
	opp = dev_pm_opp_find_bw_ceil(dev, &bwmon->min_bw_kbps, 0);
	if (IS_ERR(opp))
		return dev_err_probe(dev, ret, "failed to find min peak bandwidth\n");

	bwmon->sample_ms = data->sample_ms;
	bwmon->default_lowbw_kbps = data->default_lowbw_kbps;
	bwmon->dev = dev;

	bwmon_disable(bwmon);
	ret = devm_request_threaded_irq(dev, bwmon->irq, bwmon_intr,
					bwmon_intr_thread,
					IRQF_ONESHOT, dev_name(dev), bwmon);
	if (ret)
		return dev_err_probe(dev, ret, "failed to request IRQ\n");

	platform_set_drvdata(pdev, bwmon);
	bwmon_start(bwmon, data);

	return 0;
}

static int bwmon_remove(struct platform_device *pdev)
{
	struct icc_bwmon *bwmon = platform_get_drvdata(pdev);

	bwmon_disable(bwmon);

	return 0;
}

/* BWMON v4 */
static const struct icc_bwmon_data msm8998_bwmon_data = {
	.sample_ms = 4,
	.default_highbw_kbps = 4800 * 1024, /* 4.8 GBps */
	.default_medbw_kbps = 512 * 1024, /* 512 MBps */
	.default_lowbw_kbps = 0,
	.zone1_thres_count = 16,
	.zone3_thres_count = 1,
};

static const struct of_device_id bwmon_of_match[] = {
	{ .compatible = "qcom,msm8998-bwmon", .data = &msm8998_bwmon_data },
	{}
};
MODULE_DEVICE_TABLE(of, bwmon_of_match);

static struct platform_driver bwmon_driver = {
	.probe = bwmon_probe,
	.remove = bwmon_remove,
	.driver = {
		.name = "qcom-bwmon",
		.of_match_table = bwmon_of_match,
	},
};
module_platform_driver(bwmon_driver);

MODULE_AUTHOR("Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>");
MODULE_DESCRIPTION("QCOM BWMON driver");
MODULE_LICENSE("GPL");