// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Sophgo CV1800B SARADC Driver
 *
 *  Copyright (C) Bootlin 2024
 *  Author: Thomas Bonnefille <thomas.bonnefille@bootlin.com>
 */

#include <linux/array_size.h>
#include <linux/bitfield.h>
#include <linux/bits.h>
#include <linux/cleanup.h>
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/iopoll.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/types.h>

#include <linux/iio/iio.h>

#define CV1800B_ADC_CTRL_REG				0x04
#define	  CV1800B_ADC_EN				BIT(0)
#define	  CV1800B_ADC_SEL(x)				BIT((x) + 5)
#define CV1800B_ADC_STATUS_REG				0x08
#define	  CV1800B_ADC_BUSY				BIT(0)
#define CV1800B_ADC_CYC_SET_REG				0x0C
#define   CV1800B_MASK_STARTUP_CYCLE			GENMASK(4, 0)
#define   CV1800B_MASK_SAMPLE_WINDOW			GENMASK(11, 8)
#define   CV1800B_MASK_CLKDIV				GENMASK(15, 12)
#define   CV1800B_MASK_COMPARE_CYCLE			GENMASK(19, 16)
#define CV1800B_ADC_CH_RESULT_REG(x)			(0x14 + 4 * (x))
#define	  CV1800B_ADC_CH_RESULT				GENMASK(11, 0)
#define	  CV1800B_ADC_CH_VALID				BIT(15)
#define CV1800B_ADC_INTR_EN_REG				0x20
#define CV1800B_ADC_INTR_CLR_REG			0x24
#define	  CV1800B_ADC_INTR_CLR_BIT			BIT(0)
#define CV1800B_ADC_INTR_STA_REG			0x28
#define	  CV1800B_ADC_INTR_STA_BIT			BIT(0)
#define CV1800B_READ_TIMEOUT_MS				1000
#define CV1800B_READ_TIMEOUT_US				(CV1800B_READ_TIMEOUT_MS * 1000)

#define CV1800B_ADC_CHANNEL(index)					\
	{								\
		.type = IIO_VOLTAGE,					\
		.indexed = 1,						\
		.channel = index,					\
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),\
		.scan_index = index,					\
	}

struct cv1800b_adc {
	struct completion completion;
	void __iomem *regs;
	struct mutex lock; /* ADC Control and Result register */
	struct clk *clk;
	int irq;
};

static const struct iio_chan_spec sophgo_channels[] = {
	CV1800B_ADC_CHANNEL(0),
	CV1800B_ADC_CHANNEL(1),
	CV1800B_ADC_CHANNEL(2),
};

static void cv1800b_adc_start_measurement(struct cv1800b_adc *saradc,
					  int channel)
{
	writel(0, saradc->regs + CV1800B_ADC_CTRL_REG);
	writel(CV1800B_ADC_SEL(channel) | CV1800B_ADC_EN,
	       saradc->regs + CV1800B_ADC_CTRL_REG);
}

static int cv1800b_adc_wait(struct cv1800b_adc *saradc)
{
	if (saradc->irq < 0) {
		u32 reg;

		return readl_poll_timeout(saradc->regs + CV1800B_ADC_STATUS_REG,
					  reg, !(reg & CV1800B_ADC_BUSY),
					  500, CV1800B_READ_TIMEOUT_US);
	}

	return wait_for_completion_timeout(&saradc->completion,
					   msecs_to_jiffies(CV1800B_READ_TIMEOUT_MS)) > 0 ?
					   0 : -ETIMEDOUT;
}

static int cv1800b_adc_read_raw(struct iio_dev *indio_dev,
				struct iio_chan_spec const *chan,
				int *val, int *val2, long mask)
{
	struct cv1800b_adc *saradc = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_RAW: {
		u32 sample;

		scoped_guard(mutex, &saradc->lock) {
			int ret;

			cv1800b_adc_start_measurement(saradc, chan->scan_index);
			ret = cv1800b_adc_wait(saradc);
			if (ret < 0)
				return ret;

			sample = readl(saradc->regs + CV1800B_ADC_CH_RESULT_REG(chan->scan_index));
		}
		if (!(sample & CV1800B_ADC_CH_VALID))
			return -ENODATA;

		*val = sample & CV1800B_ADC_CH_RESULT;
		return IIO_VAL_INT;
	}
	case IIO_CHAN_INFO_SCALE:
		*val = 3300;
		*val2 = 12;
		return IIO_VAL_FRACTIONAL_LOG2;
	case IIO_CHAN_INFO_SAMP_FREQ: {
		u32 status_reg = readl(saradc->regs + CV1800B_ADC_CYC_SET_REG);
		unsigned int clk_div = (1 + FIELD_GET(CV1800B_MASK_CLKDIV, status_reg));
		unsigned int freq = clk_get_rate(saradc->clk) / clk_div;
		unsigned int nb_startup_cycle = 1 + FIELD_GET(CV1800B_MASK_STARTUP_CYCLE, status_reg);
		unsigned int nb_sample_cycle = 1 + FIELD_GET(CV1800B_MASK_SAMPLE_WINDOW, status_reg);
		unsigned int nb_compare_cycle = 1 + FIELD_GET(CV1800B_MASK_COMPARE_CYCLE, status_reg);

		*val = freq / (nb_startup_cycle + nb_sample_cycle + nb_compare_cycle);
		return IIO_VAL_INT;
	}
	default:
		return -EINVAL;
	}
}

static irqreturn_t cv1800b_adc_interrupt_handler(int irq, void *private)
{
	struct cv1800b_adc *saradc = private;
	u32 reg = readl(saradc->regs + CV1800B_ADC_INTR_STA_REG);

	if (!(FIELD_GET(CV1800B_ADC_INTR_STA_BIT, reg)))
		return IRQ_NONE;

	writel(CV1800B_ADC_INTR_CLR_BIT, saradc->regs + CV1800B_ADC_INTR_CLR_REG);
	complete(&saradc->completion);

	return IRQ_HANDLED;
}

static const struct iio_info cv1800b_adc_info = {
	.read_raw = &cv1800b_adc_read_raw,
};

static int cv1800b_adc_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct cv1800b_adc *saradc;
	struct iio_dev *indio_dev;
	int ret;

	indio_dev = devm_iio_device_alloc(dev, sizeof(*saradc));
	if (!indio_dev)
		return -ENOMEM;

	saradc = iio_priv(indio_dev);
	indio_dev->name = "sophgo-cv1800b-adc";
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->info = &cv1800b_adc_info;
	indio_dev->num_channels = ARRAY_SIZE(sophgo_channels);
	indio_dev->channels = sophgo_channels;

	saradc->clk = devm_clk_get_enabled(dev, NULL);
	if (IS_ERR(saradc->clk))
		return PTR_ERR(saradc->clk);

	saradc->regs = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(saradc->regs))
		return PTR_ERR(saradc->regs);

	saradc->irq = platform_get_irq_optional(pdev, 0);
	if (saradc->irq > 0) {
		init_completion(&saradc->completion);
		ret = devm_request_irq(dev, saradc->irq,
				       cv1800b_adc_interrupt_handler, 0,
				       dev_name(dev), saradc);
		if (ret)
			return ret;

		writel(1, saradc->regs + CV1800B_ADC_INTR_EN_REG);
	}

	ret = devm_mutex_init(dev, &saradc->lock);
	if (ret)
		return ret;

	writel(FIELD_PREP(CV1800B_MASK_STARTUP_CYCLE, 15) |
	       FIELD_PREP(CV1800B_MASK_SAMPLE_WINDOW, 15) |
	       FIELD_PREP(CV1800B_MASK_CLKDIV, 1) |
	       FIELD_PREP(CV1800B_MASK_COMPARE_CYCLE, 15),
	       saradc->regs + CV1800B_ADC_CYC_SET_REG);

	return devm_iio_device_register(dev, indio_dev);
}

static const struct of_device_id cv1800b_adc_match[] = {
	{ .compatible = "sophgo,cv1800b-saradc", },
	{ }
};
MODULE_DEVICE_TABLE(of, cv1800b_adc_match);

static struct platform_driver cv1800b_adc_driver = {
	.driver	= {
		.name		= "sophgo-cv1800b-saradc",
		.of_match_table	= cv1800b_adc_match,
	},
	.probe = cv1800b_adc_probe,
};
module_platform_driver(cv1800b_adc_driver);

MODULE_AUTHOR("Thomas Bonnefille <thomas.bonnefille@bootlin.com>");
MODULE_DESCRIPTION("Sophgo CV1800B SARADC driver");
MODULE_LICENSE("GPL");