// SPDX-License-Identifier: GPL-2.0-only
/*
 * IIO ADC driver for NXP LPC18xx ADC
 *
 * Copyright (C) 2016 Joachim Eastwood <manabian@gmail.com>
 *
 * 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/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.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,
};

static void lpc18xx_clear_cr_reg(void *data)
{
        struct lpc18xx_adc *adc = data;

        writel(0, adc->base + LPC18XX_ADC_CR);
}

static void lpc18xx_regulator_disable(void *vref)
{
        regulator_disable(vref);
}

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

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

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

        adc->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(adc->base))
                return PTR_ERR(adc->base);

        adc->clk = devm_clk_get_enabled(&pdev->dev, NULL);
        if (IS_ERR(adc->clk))
                return dev_err_probe(&pdev->dev, PTR_ERR(adc->clk),
                                     "error getting clock\n");

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

        indio_dev->name = dev_name(&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 = devm_add_action_or_reset(&pdev->dev, lpc18xx_regulator_disable, adc->vref);
        if (ret)
                return ret;

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

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

        ret = devm_add_action_or_reset(&pdev->dev, lpc18xx_clear_cr_reg, adc);
        if (ret)
                return ret;

        return devm_iio_device_register(&pdev->dev, indio_dev);
}

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

static struct platform_driver lpc18xx_adc_driver = {
        .probe  = lpc18xx_adc_probe,
        .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");