// SPDX-License-Identifier: GPL-2.0-only
//
// Copyright (C) 2020-2021 Samuel Holland <samuel@sholland.org>
//

#include <linux/clk.h>
#include <linux/devfreq.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/property.h>

#define MBUS_CR				0x0000
#define MBUS_CR_GET_DRAM_TYPE(x)	(((x) >> 16) & 0x7)
#define MBUS_CR_DRAM_TYPE_DDR2		2
#define MBUS_CR_DRAM_TYPE_DDR3		3
#define MBUS_CR_DRAM_TYPE_DDR4		4
#define MBUS_CR_DRAM_TYPE_LPDDR2	6
#define MBUS_CR_DRAM_TYPE_LPDDR3	7

#define MBUS_TMR			0x000c
#define MBUS_TMR_PERIOD(x)		((x) - 1)

#define MBUS_PMU_CFG			0x009c
#define MBUS_PMU_CFG_PERIOD(x)		(((x) - 1) << 16)
#define MBUS_PMU_CFG_UNIT		(0x3 << 1)
#define MBUS_PMU_CFG_UNIT_B		(0x0 << 1)
#define MBUS_PMU_CFG_UNIT_KB		(0x1 << 1)
#define MBUS_PMU_CFG_UNIT_MB		(0x2 << 1)
#define MBUS_PMU_CFG_ENABLE		(0x1 << 0)

#define MBUS_PMU_BWCR(n)		(0x00a0 + (0x04 * (n)))

#define MBUS_TOTAL_BWCR			MBUS_PMU_BWCR(5)
#define MBUS_TOTAL_BWCR_H616		MBUS_PMU_BWCR(13)

#define MBUS_MDFSCR			0x0100
#define MBUS_MDFSCR_BUFFER_TIMING	(0x1 << 15)
#define MBUS_MDFSCR_PAD_HOLD		(0x1 << 13)
#define MBUS_MDFSCR_BYPASS		(0x1 << 4)
#define MBUS_MDFSCR_MODE		(0x1 << 1)
#define MBUS_MDFSCR_MODE_DFS		(0x0 << 1)
#define MBUS_MDFSCR_MODE_CFS		(0x1 << 1)
#define MBUS_MDFSCR_START		(0x1 << 0)

#define MBUS_MDFSMRMR			0x0108

#define DRAM_PWRCTL			0x0004
#define DRAM_PWRCTL_SELFREF_EN		(0x1 << 0)

#define DRAM_RFSHTMG			0x0090
#define DRAM_RFSHTMG_TREFI(x)		((x) << 16)
#define DRAM_RFSHTMG_TRFC(x)		((x) << 0)

#define DRAM_VTFCR			0x00b8
#define DRAM_VTFCR_VTF_ENABLE		(0x3 << 8)

#define DRAM_ODTMAP			0x0120

#define DRAM_DX_MAX			4

#define DRAM_DXnGCR0(n)			(0x0344 + 0x80 * (n))
#define DRAM_DXnGCR0_DXODT		(0x3 << 4)
#define DRAM_DXnGCR0_DXODT_DYNAMIC	(0x0 << 4)
#define DRAM_DXnGCR0_DXODT_ENABLED	(0x1 << 4)
#define DRAM_DXnGCR0_DXODT_DISABLED	(0x2 << 4)
#define DRAM_DXnGCR0_DXEN		(0x1 << 0)

struct sun8i_a33_mbus_variant {
	u32					min_dram_divider;
	u32					max_dram_divider;
	u32					odt_freq_mhz;
};

struct sun8i_a33_mbus {
	const struct sun8i_a33_mbus_variant	*variant;
	void __iomem				*reg_dram;
	void __iomem				*reg_mbus;
	struct clk				*clk_bus;
	struct clk				*clk_dram;
	struct clk				*clk_mbus;
	struct devfreq				*devfreq_dram;
	struct devfreq_simple_ondemand_data	gov_data;
	struct devfreq_dev_profile		profile;
	u32					data_width;
	u32					nominal_bw;
	u32					odtmap;
	u32					tREFI_ns;
	u32					tRFC_ns;
	unsigned long				freq_table[];
};

/*
 * The unit for this value is (MBUS clock cycles / MBUS_TMR_PERIOD). When
 * MBUS_TMR_PERIOD is programmed to match the MBUS clock frequency in MHz, as
 * it is during DRAM init and during probe, the resulting unit is microseconds.
 */
static int pmu_period = 50000;
module_param(pmu_period, int, 0644);
MODULE_PARM_DESC(pmu_period, "Bandwidth measurement period (microseconds)");

static u32 sun8i_a33_mbus_get_peak_bw(struct sun8i_a33_mbus *priv)
{
	/* Returns the peak transfer (in KiB) during any single PMU period. */
	return readl_relaxed(priv->reg_mbus + MBUS_TOTAL_BWCR);
}

static void sun8i_a33_mbus_restart_pmu_counters(struct sun8i_a33_mbus *priv)
{
	u32 pmu_cfg = MBUS_PMU_CFG_PERIOD(pmu_period) | MBUS_PMU_CFG_UNIT_KB;

	/* All PMU counters are cleared on a disable->enable transition. */
	writel_relaxed(pmu_cfg,
		       priv->reg_mbus + MBUS_PMU_CFG);
	writel_relaxed(pmu_cfg | MBUS_PMU_CFG_ENABLE,
		       priv->reg_mbus + MBUS_PMU_CFG);

}

static void sun8i_a33_mbus_update_nominal_bw(struct sun8i_a33_mbus *priv,
					     u32 ddr_freq_mhz)
{
	/*
	 * Nominal bandwidth (KiB per PMU period):
	 *
	 *   DDR transfers   microseconds     KiB
	 *   ------------- * ------------ * --------
	 *    microsecond     PMU period    transfer
	 */
	priv->nominal_bw = ddr_freq_mhz * pmu_period * priv->data_width / 1024;
}

static int sun8i_a33_mbus_set_dram_freq(struct sun8i_a33_mbus *priv,
					unsigned long freq)
{
	u32  ddr_freq_mhz = freq / USEC_PER_SEC; /* DDR */
	u32 dram_freq_mhz =    ddr_freq_mhz / 2; /* SDR */
	u32 mctl_freq_mhz =   dram_freq_mhz / 2; /* HDR */
	u32 dxodt, mdfscr, pwrctl, vtfcr;
	u32 i, tREFI_32ck, tRFC_ck;
	int ret;

	/* The rate change is not effective until the MDFS process runs. */
	ret = clk_set_rate(priv->clk_dram, freq);
	if (ret)
		return ret;

	/* Disable automatic self-refesh and VTF before starting MDFS. */
	pwrctl = readl_relaxed(priv->reg_dram + DRAM_PWRCTL) &
		 ~DRAM_PWRCTL_SELFREF_EN;
	writel_relaxed(pwrctl, priv->reg_dram + DRAM_PWRCTL);
	vtfcr = readl_relaxed(priv->reg_dram + DRAM_VTFCR);
	writel_relaxed(vtfcr & ~DRAM_VTFCR_VTF_ENABLE,
		       priv->reg_dram + DRAM_VTFCR);

	/* Set up MDFS and enable double buffering for timing registers. */
	mdfscr = MBUS_MDFSCR_MODE_DFS |
		 MBUS_MDFSCR_BYPASS |
		 MBUS_MDFSCR_PAD_HOLD |
		 MBUS_MDFSCR_BUFFER_TIMING;
	writel(mdfscr, priv->reg_mbus + MBUS_MDFSCR);

	/* Update the buffered copy of RFSHTMG. */
	tREFI_32ck = priv->tREFI_ns * mctl_freq_mhz / 1000 / 32;
	tRFC_ck = DIV_ROUND_UP(priv->tRFC_ns * mctl_freq_mhz, 1000);
	writel(DRAM_RFSHTMG_TREFI(tREFI_32ck) | DRAM_RFSHTMG_TRFC(tRFC_ck),
	       priv->reg_dram + DRAM_RFSHTMG);

	/* Enable ODT if needed, or disable it to save power. */
	if (priv->odtmap && dram_freq_mhz > priv->variant->odt_freq_mhz) {
		dxodt = DRAM_DXnGCR0_DXODT_DYNAMIC;
		writel(priv->odtmap, priv->reg_dram + DRAM_ODTMAP);
	} else {
		dxodt = DRAM_DXnGCR0_DXODT_DISABLED;
		writel(0, priv->reg_dram + DRAM_ODTMAP);
	}
	for (i = 0; i < DRAM_DX_MAX; ++i) {
		void __iomem *reg = priv->reg_dram + DRAM_DXnGCR0(i);

		writel((readl(reg) & ~DRAM_DXnGCR0_DXODT) | dxodt, reg);
	}

	dev_dbg(priv->devfreq_dram->dev.parent,
		"Setting DRAM to %u MHz, tREFI=%u, tRFC=%u, ODT=%s\n",
		dram_freq_mhz, tREFI_32ck, tRFC_ck,
		dxodt == DRAM_DXnGCR0_DXODT_DYNAMIC ? "dynamic" : "disabled");

	/* Trigger hardware MDFS. */
	writel(mdfscr | MBUS_MDFSCR_START, priv->reg_mbus + MBUS_MDFSCR);
	ret = readl_poll_timeout_atomic(priv->reg_mbus + MBUS_MDFSCR, mdfscr,
					!(mdfscr & MBUS_MDFSCR_START), 10, 1000);
	if (ret)
		return ret;

	/* Disable double buffering. */
	writel(0, priv->reg_mbus + MBUS_MDFSCR);

	/* Restore VTF configuration. */
	writel_relaxed(vtfcr, priv->reg_dram + DRAM_VTFCR);

	/* Enable automatic self-refresh at the lowest frequency only. */
	if (freq == priv->freq_table[0])
		pwrctl |= DRAM_PWRCTL_SELFREF_EN;
	writel_relaxed(pwrctl, priv->reg_dram + DRAM_PWRCTL);

	sun8i_a33_mbus_restart_pmu_counters(priv);
	sun8i_a33_mbus_update_nominal_bw(priv, ddr_freq_mhz);

	return 0;
}

static int sun8i_a33_mbus_set_dram_target(struct device *dev,
					  unsigned long *freq, u32 flags)
{
	struct sun8i_a33_mbus *priv = dev_get_drvdata(dev);
	struct devfreq *devfreq = priv->devfreq_dram;
	struct dev_pm_opp *opp;
	int ret;

	opp = devfreq_recommended_opp(dev, freq, flags);
	if (IS_ERR(opp))
		return PTR_ERR(opp);

	dev_pm_opp_put(opp);

	if (*freq == devfreq->previous_freq)
		return 0;

	ret = sun8i_a33_mbus_set_dram_freq(priv, *freq);
	if (ret) {
		dev_warn(dev, "failed to set DRAM frequency: %d\n", ret);
		*freq = devfreq->previous_freq;
	}

	return ret;
}

static int sun8i_a33_mbus_get_dram_status(struct device *dev,
					  struct devfreq_dev_status *stat)
{
	struct sun8i_a33_mbus *priv = dev_get_drvdata(dev);

	stat->busy_time		= sun8i_a33_mbus_get_peak_bw(priv);
	stat->total_time	= priv->nominal_bw;
	stat->current_frequency	= priv->devfreq_dram->previous_freq;

	sun8i_a33_mbus_restart_pmu_counters(priv);

	dev_dbg(dev, "Using %lu/%lu (%lu%%) at %lu MHz\n",
		stat->busy_time, stat->total_time,
		DIV_ROUND_CLOSEST(stat->busy_time * 100, stat->total_time),
		stat->current_frequency / USEC_PER_SEC);

	return 0;
}

static int sun8i_a33_mbus_hw_init(struct device *dev,
				  struct sun8i_a33_mbus *priv,
				  unsigned long ddr_freq)
{
	u32 i, mbus_cr, mbus_freq_mhz;

	/* Choose tREFI and tRFC to match the configured DRAM type. */
	mbus_cr = readl_relaxed(priv->reg_mbus + MBUS_CR);
	switch (MBUS_CR_GET_DRAM_TYPE(mbus_cr)) {
	case MBUS_CR_DRAM_TYPE_DDR2:
	case MBUS_CR_DRAM_TYPE_DDR3:
	case MBUS_CR_DRAM_TYPE_DDR4:
		priv->tREFI_ns = 7800;
		priv->tRFC_ns = 350;
		break;
	case MBUS_CR_DRAM_TYPE_LPDDR2:
	case MBUS_CR_DRAM_TYPE_LPDDR3:
		priv->tREFI_ns = 3900;
		priv->tRFC_ns = 210;
		break;
	default:
		return -EINVAL;
	}

	/* Save ODTMAP so it can be restored when raising the frequency. */
	priv->odtmap = readl_relaxed(priv->reg_dram + DRAM_ODTMAP);

	/* Compute the DRAM data bus width by counting enabled DATx8 blocks. */
	for (i = 0; i < DRAM_DX_MAX; ++i) {
		void __iomem *reg = priv->reg_dram + DRAM_DXnGCR0(i);

		if (!(readl_relaxed(reg) & DRAM_DXnGCR0_DXEN))
			break;
	}
	priv->data_width = i;

	dev_dbg(dev, "Detected %u-bit %sDDRx with%s ODT\n",
		priv->data_width * 8,
		MBUS_CR_GET_DRAM_TYPE(mbus_cr) > 4 ? "LP" : "",
		priv->odtmap ? "" : "out");

	/* Program MBUS_TMR such that the PMU period unit is microseconds. */
	mbus_freq_mhz = clk_get_rate(priv->clk_mbus) / USEC_PER_SEC;
	writel_relaxed(MBUS_TMR_PERIOD(mbus_freq_mhz),
		       priv->reg_mbus + MBUS_TMR);

	/* "Master Ready Mask Register" bits must be set or MDFS will block. */
	writel_relaxed(0xffffffff, priv->reg_mbus + MBUS_MDFSMRMR);

	sun8i_a33_mbus_restart_pmu_counters(priv);
	sun8i_a33_mbus_update_nominal_bw(priv, ddr_freq / USEC_PER_SEC);

	return 0;
}

static int __maybe_unused sun8i_a33_mbus_suspend(struct device *dev)
{
	struct sun8i_a33_mbus *priv = dev_get_drvdata(dev);

	clk_disable_unprepare(priv->clk_bus);

	return 0;
}

static int __maybe_unused sun8i_a33_mbus_resume(struct device *dev)
{
	struct sun8i_a33_mbus *priv = dev_get_drvdata(dev);

	return clk_prepare_enable(priv->clk_bus);
}

static int sun8i_a33_mbus_probe(struct platform_device *pdev)
{
	const struct sun8i_a33_mbus_variant *variant;
	struct device *dev = &pdev->dev;
	struct sun8i_a33_mbus *priv;
	unsigned long base_freq;
	unsigned int max_state;
	const char *err;
	int i, ret;

	variant = device_get_match_data(dev);
	if (!variant)
		return -EINVAL;

	max_state = variant->max_dram_divider - variant->min_dram_divider + 1;

	priv = devm_kzalloc(dev, struct_size(priv, freq_table, max_state), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	platform_set_drvdata(pdev, priv);

	priv->variant = variant;

	priv->reg_dram = devm_platform_ioremap_resource_byname(pdev, "dram");
	if (IS_ERR(priv->reg_dram))
		return PTR_ERR(priv->reg_dram);

	priv->reg_mbus = devm_platform_ioremap_resource_byname(pdev, "mbus");
	if (IS_ERR(priv->reg_mbus))
		return PTR_ERR(priv->reg_mbus);

	priv->clk_bus = devm_clk_get(dev, "bus");
	if (IS_ERR(priv->clk_bus))
		return dev_err_probe(dev, PTR_ERR(priv->clk_bus),
				     "failed to get bus clock\n");

	priv->clk_dram = devm_clk_get(dev, "dram");
	if (IS_ERR(priv->clk_dram))
		return dev_err_probe(dev, PTR_ERR(priv->clk_dram),
				     "failed to get dram clock\n");

	priv->clk_mbus = devm_clk_get(dev, "mbus");
	if (IS_ERR(priv->clk_mbus))
		return dev_err_probe(dev, PTR_ERR(priv->clk_mbus),
				     "failed to get mbus clock\n");

	ret = clk_prepare_enable(priv->clk_bus);
	if (ret)
		return dev_err_probe(dev, ret,
				     "failed to enable bus clock\n");

	/* Lock the DRAM clock rate to keep priv->nominal_bw in sync. */
	ret = clk_rate_exclusive_get(priv->clk_dram);
	if (ret) {
		err = "failed to lock dram clock rate\n";
		goto err_disable_bus;
	}

	/* Lock the MBUS clock rate to keep MBUS_TMR_PERIOD in sync. */
	ret = clk_rate_exclusive_get(priv->clk_mbus);
	if (ret) {
		err = "failed to lock mbus clock rate\n";
		goto err_unlock_dram;
	}

	priv->gov_data.upthreshold	= 10;
	priv->gov_data.downdifferential	=  5;

	priv->profile.initial_freq	= clk_get_rate(priv->clk_dram);
	priv->profile.polling_ms	= 1000;
	priv->profile.target		= sun8i_a33_mbus_set_dram_target;
	priv->profile.get_dev_status	= sun8i_a33_mbus_get_dram_status;
	priv->profile.freq_table	= priv->freq_table;
	priv->profile.max_state		= max_state;

	ret = devm_pm_opp_set_clkname(dev, "dram");
	if (ret) {
		err = "failed to add OPP table\n";
		goto err_unlock_mbus;
	}

	base_freq = clk_get_rate(clk_get_parent(priv->clk_dram));
	for (i = 0; i < max_state; ++i) {
		unsigned int div = variant->max_dram_divider - i;

		priv->freq_table[i] = base_freq / div;

		ret = dev_pm_opp_add(dev, priv->freq_table[i], 0);
		if (ret) {
			err = "failed to add OPPs\n";
			goto err_remove_opps;
		}
	}

	ret = sun8i_a33_mbus_hw_init(dev, priv, priv->profile.initial_freq);
	if (ret) {
		err = "failed to init hardware\n";
		goto err_remove_opps;
	}

	priv->devfreq_dram = devfreq_add_device(dev, &priv->profile,
						DEVFREQ_GOV_SIMPLE_ONDEMAND,
						&priv->gov_data);
	if (IS_ERR(priv->devfreq_dram)) {
		ret = PTR_ERR(priv->devfreq_dram);
		err = "failed to add devfreq device\n";
		goto err_remove_opps;
	}

	/*
	 * This must be set manually after registering the devfreq device,
	 * because there is no way to select a dynamic OPP as the suspend OPP.
	 */
	priv->devfreq_dram->suspend_freq = priv->freq_table[0];

	return 0;

err_remove_opps:
	dev_pm_opp_remove_all_dynamic(dev);
err_unlock_mbus:
	clk_rate_exclusive_put(priv->clk_mbus);
err_unlock_dram:
	clk_rate_exclusive_put(priv->clk_dram);
err_disable_bus:
	clk_disable_unprepare(priv->clk_bus);

	return dev_err_probe(dev, ret, err);
}

static int sun8i_a33_mbus_remove(struct platform_device *pdev)
{
	struct sun8i_a33_mbus *priv = platform_get_drvdata(pdev);
	unsigned long initial_freq = priv->profile.initial_freq;
	struct device *dev = &pdev->dev;
	int ret;

	devfreq_remove_device(priv->devfreq_dram);

	ret = sun8i_a33_mbus_set_dram_freq(priv, initial_freq);
	if (ret)
		dev_warn(dev, "failed to restore DRAM frequency: %d\n", ret);

	dev_pm_opp_remove_all_dynamic(dev);
	clk_rate_exclusive_put(priv->clk_mbus);
	clk_rate_exclusive_put(priv->clk_dram);
	clk_disable_unprepare(priv->clk_bus);

	return 0;
}

static const struct sun8i_a33_mbus_variant sun50i_a64_mbus = {
	.min_dram_divider	= 1,
	.max_dram_divider	= 4,
	.odt_freq_mhz		= 400,
};

static const struct of_device_id sun8i_a33_mbus_of_match[] = {
	{ .compatible = "allwinner,sun50i-a64-mbus", .data = &sun50i_a64_mbus },
	{ .compatible = "allwinner,sun50i-h5-mbus", .data = &sun50i_a64_mbus },
	{ },
};
MODULE_DEVICE_TABLE(of, sun8i_a33_mbus_of_match);

static SIMPLE_DEV_PM_OPS(sun8i_a33_mbus_pm_ops,
			 sun8i_a33_mbus_suspend, sun8i_a33_mbus_resume);

static struct platform_driver sun8i_a33_mbus_driver = {
	.probe	= sun8i_a33_mbus_probe,
	.remove	= sun8i_a33_mbus_remove,
	.driver	= {
		.name		= "sun8i-a33-mbus",
		.of_match_table	= sun8i_a33_mbus_of_match,
		.pm		= pm_ptr(&sun8i_a33_mbus_pm_ops),
	},
};
module_platform_driver(sun8i_a33_mbus_driver);

MODULE_AUTHOR("Samuel Holland <samuel@sholland.org>");
MODULE_DESCRIPTION("Allwinner sun8i/sun50i MBUS DEVFREQ Driver");
MODULE_LICENSE("GPL v2");