/*
 * IIO ADC driver for NXP LPC18xx ADC
 *
 * Copyright (C) 2016 Joachim Eastwood <manabian@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * UNSUPPORTED hardware features:
 *  - Hardware triggers
 *  - Burst mode
 *  - Interrupts
 *  - DMA
 */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/iio/iio.h>
#include <linux/iio/driver.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/regulator/consumer.h>

/* LPC18XX ADC registers and bits */
#define LPC18XX_ADC_CR			0x000
#define  LPC18XX_ADC_CR_CLKDIV_SHIFT	8
#define  LPC18XX_ADC_CR_PDN		BIT(21)
#define  LPC18XX_ADC_CR_START_NOW	(0x1 << 24)
#define LPC18XX_ADC_GDR			0x004

/* Data register bits */
#define LPC18XX_ADC_SAMPLE_SHIFT	6
#define LPC18XX_ADC_SAMPLE_MASK		0x3ff
#define LPC18XX_ADC_CONV_DONE		BIT(31)

/* Clock should be 4.5 MHz or less */
#define LPC18XX_ADC_CLK_TARGET		4500000

struct lpc18xx_adc {
	struct regulator *vref;
	void __iomem *base;
	struct device *dev;
	struct mutex lock;
	struct clk *clk;
	u32 cr_reg;
};

#define LPC18XX_ADC_CHAN(_idx) {				\
	.type = IIO_VOLTAGE,					\
	.indexed = 1,						\
	.channel = _idx,					\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
}

static const struct iio_chan_spec lpc18xx_adc_iio_channels[] = {
	LPC18XX_ADC_CHAN(0),
	LPC18XX_ADC_CHAN(1),
	LPC18XX_ADC_CHAN(2),
	LPC18XX_ADC_CHAN(3),
	LPC18XX_ADC_CHAN(4),
	LPC18XX_ADC_CHAN(5),
	LPC18XX_ADC_CHAN(6),
	LPC18XX_ADC_CHAN(7),
};

static int lpc18xx_adc_read_chan(struct lpc18xx_adc *adc, unsigned int ch)
{
	int ret;
	u32 reg;

	reg = adc->cr_reg | BIT(ch) | LPC18XX_ADC_CR_START_NOW;
	writel(reg, adc->base + LPC18XX_ADC_CR);

	ret = readl_poll_timeout(adc->base + LPC18XX_ADC_GDR, reg,
				 reg & LPC18XX_ADC_CONV_DONE, 3, 9);
	if (ret) {
		dev_warn(adc->dev, "adc read timed out\n");
		return ret;
	}

	return (reg >> LPC18XX_ADC_SAMPLE_SHIFT) & LPC18XX_ADC_SAMPLE_MASK;
}

static int lpc18xx_adc_read_raw(struct iio_dev *indio_dev,
				struct iio_chan_spec const *chan,
				int *val, int *val2, long mask)
{
	struct lpc18xx_adc *adc = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		mutex_lock(&adc->lock);
		*val = lpc18xx_adc_read_chan(adc, chan->channel);
		mutex_unlock(&adc->lock);
		if (*val < 0)
			return *val;

		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:
		*val = regulator_get_voltage(adc->vref) / 1000;
		*val2 = 10;

		return IIO_VAL_FRACTIONAL_LOG2;
	}

	return -EINVAL;
}

static const struct iio_info lpc18xx_adc_info = {
	.read_raw = lpc18xx_adc_read_raw,
	.driver_module = THIS_MODULE,
};

static int lpc18xx_adc_probe(struct platform_device *pdev)
{
	struct iio_dev *indio_dev;
	struct lpc18xx_adc *adc;
	struct resource *res;
	unsigned int clkdiv;
	unsigned long rate;
	int ret;

	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*adc));
	if (!indio_dev)
		return -ENOMEM;

	platform_set_drvdata(pdev, indio_dev);
	adc = iio_priv(indio_dev);
	adc->dev = &pdev->dev;
	mutex_init(&adc->lock);

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	adc->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(adc->base))
		return PTR_ERR(adc->base);

	adc->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(adc->clk)) {
		dev_err(&pdev->dev, "error getting clock\n");
		return PTR_ERR(adc->clk);
	}

	rate = clk_get_rate(adc->clk);
	clkdiv = DIV_ROUND_UP(rate, LPC18XX_ADC_CLK_TARGET);

	adc->vref = devm_regulator_get(&pdev->dev, "vref");
	if (IS_ERR(adc->vref)) {
		dev_err(&pdev->dev, "error getting regulator\n");
		return PTR_ERR(adc->vref);
	}

	indio_dev->name = dev_name(&pdev->dev);
	indio_dev->dev.parent = &pdev->dev;
	indio_dev->info = &lpc18xx_adc_info;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = lpc18xx_adc_iio_channels;
	indio_dev->num_channels = ARRAY_SIZE(lpc18xx_adc_iio_channels);

	ret = regulator_enable(adc->vref);
	if (ret) {
		dev_err(&pdev->dev, "unable to enable regulator\n");
		return ret;
	}

	ret = clk_prepare_enable(adc->clk);
	if (ret) {
		dev_err(&pdev->dev, "unable to enable clock\n");
		goto dis_reg;
	}

	adc->cr_reg = (clkdiv << LPC18XX_ADC_CR_CLKDIV_SHIFT) |
			LPC18XX_ADC_CR_PDN;
	writel(adc->cr_reg, adc->base + LPC18XX_ADC_CR);

	ret = iio_device_register(indio_dev);
	if (ret) {
		dev_err(&pdev->dev, "unable to register device\n");
		goto dis_clk;
	}

	return 0;

dis_clk:
	writel(0, adc->base + LPC18XX_ADC_CR);
	clk_disable_unprepare(adc->clk);
dis_reg:
	regulator_disable(adc->vref);
	return ret;
}

static int lpc18xx_adc_remove(struct platform_device *pdev)
{
	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
	struct lpc18xx_adc *adc = iio_priv(indio_dev);

	iio_device_unregister(indio_dev);

	writel(0, adc->base + LPC18XX_ADC_CR);
	clk_disable_unprepare(adc->clk);
	regulator_disable(adc->vref);

	return 0;
}

static const struct of_device_id lpc18xx_adc_match[] = {
	{ .compatible = "nxp,lpc1850-adc" },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, lpc18xx_adc_match);

static struct platform_driver lpc18xx_adc_driver = {
	.probe	= lpc18xx_adc_probe,
	.remove	= lpc18xx_adc_remove,
	.driver	= {
		.name = "lpc18xx-adc",
		.of_match_table = lpc18xx_adc_match,
	},
};
module_platform_driver(lpc18xx_adc_driver);

MODULE_DESCRIPTION("LPC18xx ADC driver");
MODULE_AUTHOR("Joachim Eastwood <manabian@gmail.com>");
MODULE_LICENSE("GPL v2");