/*
 * Amlogic Meson Successive Approximation Register (SAR) A/D Converter
 *
 * Copyright (C) 2017 Martin Blumenstingl <martin.blumenstingl@googlemail.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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/bitfield.h>
#include <linux/clk.h>
#include <linux/clk-provider.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/iio/iio.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/regulator/consumer.h>

#define MESON_SAR_ADC_REG0					0x00
	#define MESON_SAR_ADC_REG0_PANEL_DETECT			BIT(31)
	#define MESON_SAR_ADC_REG0_BUSY_MASK			GENMASK(30, 28)
	#define MESON_SAR_ADC_REG0_DELTA_BUSY			BIT(30)
	#define MESON_SAR_ADC_REG0_AVG_BUSY			BIT(29)
	#define MESON_SAR_ADC_REG0_SAMPLE_BUSY			BIT(28)
	#define MESON_SAR_ADC_REG0_FIFO_FULL			BIT(27)
	#define MESON_SAR_ADC_REG0_FIFO_EMPTY			BIT(26)
	#define MESON_SAR_ADC_REG0_FIFO_COUNT_MASK		GENMASK(25, 21)
	#define MESON_SAR_ADC_REG0_ADC_BIAS_CTRL_MASK		GENMASK(20, 19)
	#define MESON_SAR_ADC_REG0_CURR_CHAN_ID_MASK		GENMASK(18, 16)
	#define MESON_SAR_ADC_REG0_ADC_TEMP_SEN_SEL		BIT(15)
	#define MESON_SAR_ADC_REG0_SAMPLING_STOP		BIT(14)
	#define MESON_SAR_ADC_REG0_CHAN_DELTA_EN_MASK		GENMASK(13, 12)
	#define MESON_SAR_ADC_REG0_DETECT_IRQ_POL		BIT(10)
	#define MESON_SAR_ADC_REG0_DETECT_IRQ_EN		BIT(9)
	#define MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK		GENMASK(8, 4)
	#define MESON_SAR_ADC_REG0_FIFO_IRQ_EN			BIT(3)
	#define MESON_SAR_ADC_REG0_SAMPLING_START		BIT(2)
	#define MESON_SAR_ADC_REG0_CONTINUOUS_EN		BIT(1)
	#define MESON_SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE		BIT(0)

#define MESON_SAR_ADC_CHAN_LIST					0x04
	#define MESON_SAR_ADC_CHAN_LIST_MAX_INDEX_MASK		GENMASK(26, 24)
	#define MESON_SAR_ADC_CHAN_LIST_ENTRY_MASK(_chan)	\
					(GENMASK(2, 0) << ((_chan) * 3))

#define MESON_SAR_ADC_AVG_CNTL					0x08
	#define MESON_SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(_chan)	\
					(16 + ((_chan) * 2))
	#define MESON_SAR_ADC_AVG_CNTL_AVG_MODE_MASK(_chan)	\
					(GENMASK(17, 16) << ((_chan) * 2))
	#define MESON_SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(_chan)	\
					(0 + ((_chan) * 2))
	#define MESON_SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(_chan)	\
					(GENMASK(1, 0) << ((_chan) * 2))

#define MESON_SAR_ADC_REG3					0x0c
	#define MESON_SAR_ADC_REG3_CNTL_USE_SC_DLY		BIT(31)
	#define MESON_SAR_ADC_REG3_CLK_EN			BIT(30)
	#define MESON_SAR_ADC_REG3_BL30_INITIALIZED		BIT(28)
	#define MESON_SAR_ADC_REG3_CTRL_CONT_RING_COUNTER_EN	BIT(27)
	#define MESON_SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE	BIT(26)
	#define MESON_SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK	GENMASK(25, 23)
	#define MESON_SAR_ADC_REG3_DETECT_EN			BIT(22)
	#define MESON_SAR_ADC_REG3_ADC_EN			BIT(21)
	#define MESON_SAR_ADC_REG3_PANEL_DETECT_COUNT_MASK	GENMASK(20, 18)
	#define MESON_SAR_ADC_REG3_PANEL_DETECT_FILTER_TB_MASK	GENMASK(17, 16)
	#define MESON_SAR_ADC_REG3_ADC_CLK_DIV_SHIFT		10
	#define MESON_SAR_ADC_REG3_ADC_CLK_DIV_WIDTH		5
	#define MESON_SAR_ADC_REG3_BLOCK_DLY_SEL_MASK		GENMASK(9, 8)
	#define MESON_SAR_ADC_REG3_BLOCK_DLY_MASK		GENMASK(7, 0)

#define MESON_SAR_ADC_DELAY					0x10
	#define MESON_SAR_ADC_DELAY_INPUT_DLY_SEL_MASK		GENMASK(25, 24)
	#define MESON_SAR_ADC_DELAY_BL30_BUSY			BIT(15)
	#define MESON_SAR_ADC_DELAY_KERNEL_BUSY			BIT(14)
	#define MESON_SAR_ADC_DELAY_INPUT_DLY_CNT_MASK		GENMASK(23, 16)
	#define MESON_SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK		GENMASK(9, 8)
	#define MESON_SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK		GENMASK(7, 0)

#define MESON_SAR_ADC_LAST_RD					0x14
	#define MESON_SAR_ADC_LAST_RD_LAST_CHANNEL1_MASK	GENMASK(23, 16)
	#define MESON_SAR_ADC_LAST_RD_LAST_CHANNEL0_MASK	GENMASK(9, 0)

#define MESON_SAR_ADC_FIFO_RD					0x18
	#define MESON_SAR_ADC_FIFO_RD_CHAN_ID_MASK		GENMASK(14, 12)
	#define MESON_SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK		GENMASK(11, 0)

#define MESON_SAR_ADC_AUX_SW					0x1c
	#define MESON_SAR_ADC_AUX_SW_MUX_SEL_CHAN_MASK(_chan)	\
					(GENMASK(10, 8) << (((_chan) - 2) * 2))
	#define MESON_SAR_ADC_AUX_SW_VREF_P_MUX			BIT(6)
	#define MESON_SAR_ADC_AUX_SW_VREF_N_MUX			BIT(5)
	#define MESON_SAR_ADC_AUX_SW_MODE_SEL			BIT(4)
	#define MESON_SAR_ADC_AUX_SW_YP_DRIVE_SW		BIT(3)
	#define MESON_SAR_ADC_AUX_SW_XP_DRIVE_SW		BIT(2)
	#define MESON_SAR_ADC_AUX_SW_YM_DRIVE_SW		BIT(1)
	#define MESON_SAR_ADC_AUX_SW_XM_DRIVE_SW		BIT(0)

#define MESON_SAR_ADC_CHAN_10_SW				0x20
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_MUX_SEL_MASK	GENMASK(25, 23)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_VREF_P_MUX	BIT(22)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_VREF_N_MUX	BIT(21)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_MODE_SEL		BIT(20)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_YP_DRIVE_SW	BIT(19)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_XP_DRIVE_SW	BIT(18)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_YM_DRIVE_SW	BIT(17)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_XM_DRIVE_SW	BIT(16)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_MUX_SEL_MASK	GENMASK(9, 7)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_VREF_P_MUX	BIT(6)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_VREF_N_MUX	BIT(5)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_MODE_SEL		BIT(4)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_YP_DRIVE_SW	BIT(3)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_XP_DRIVE_SW	BIT(2)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_YM_DRIVE_SW	BIT(1)
	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_XM_DRIVE_SW	BIT(0)

#define MESON_SAR_ADC_DETECT_IDLE_SW				0x24
	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_SW_EN	BIT(26)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_MUX_MASK	GENMASK(25, 23)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_VREF_P_MUX	BIT(22)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_VREF_N_MUX	BIT(21)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_SEL	BIT(20)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_YP_DRIVE_SW	BIT(19)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_XP_DRIVE_SW	BIT(18)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_YM_DRIVE_SW	BIT(17)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_XM_DRIVE_SW	BIT(16)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_MUX_SEL_MASK	GENMASK(9, 7)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_VREF_P_MUX	BIT(6)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_VREF_N_MUX	BIT(5)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_SEL	BIT(4)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_YP_DRIVE_SW	BIT(3)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_XP_DRIVE_SW	BIT(2)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_YM_DRIVE_SW	BIT(1)
	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_XM_DRIVE_SW	BIT(0)

#define MESON_SAR_ADC_DELTA_10					0x28
	#define MESON_SAR_ADC_DELTA_10_TEMP_SEL			BIT(27)
	#define MESON_SAR_ADC_DELTA_10_TS_REVE1			BIT(26)
	#define MESON_SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_MASK	GENMASK(25, 16)
	#define MESON_SAR_ADC_DELTA_10_TS_REVE0			BIT(15)
	#define MESON_SAR_ADC_DELTA_10_TS_C_SHIFT		11
	#define MESON_SAR_ADC_DELTA_10_TS_C_MASK		GENMASK(14, 11)
	#define MESON_SAR_ADC_DELTA_10_TS_VBG_EN		BIT(10)
	#define MESON_SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_MASK	GENMASK(9, 0)

/*
 * NOTE: registers from here are undocumented (the vendor Linux kernel driver
 * and u-boot source served as reference). These only seem to be relevant on
 * GXBB and newer.
 */
#define MESON_SAR_ADC_REG11					0x2c
	#define MESON_SAR_ADC_REG11_BANDGAP_EN			BIT(13)

#define MESON_SAR_ADC_REG13					0x34
	#define MESON_SAR_ADC_REG13_12BIT_CALIBRATION_MASK	GENMASK(13, 8)

#define MESON_SAR_ADC_MAX_FIFO_SIZE				32
#define MESON_SAR_ADC_TIMEOUT					100 /* ms */
/* for use with IIO_VAL_INT_PLUS_MICRO */
#define MILLION							1000000

#define MESON_SAR_ADC_CHAN(_chan) {					\
	.type = IIO_VOLTAGE,						\
	.indexed = 1,							\
	.channel = _chan,						\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
				BIT(IIO_CHAN_INFO_AVERAGE_RAW),		\
	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |		\
				BIT(IIO_CHAN_INFO_CALIBBIAS) |		\
				BIT(IIO_CHAN_INFO_CALIBSCALE),		\
	.datasheet_name = "SAR_ADC_CH"#_chan,				\
}

/*
 * TODO: the hardware supports IIO_TEMP for channel 6 as well which is
 * currently not supported by this driver.
 */
static const struct iio_chan_spec meson_sar_adc_iio_channels[] = {
	MESON_SAR_ADC_CHAN(0),
	MESON_SAR_ADC_CHAN(1),
	MESON_SAR_ADC_CHAN(2),
	MESON_SAR_ADC_CHAN(3),
	MESON_SAR_ADC_CHAN(4),
	MESON_SAR_ADC_CHAN(5),
	MESON_SAR_ADC_CHAN(6),
	MESON_SAR_ADC_CHAN(7),
	IIO_CHAN_SOFT_TIMESTAMP(8),
};

enum meson_sar_adc_avg_mode {
	NO_AVERAGING = 0x0,
	MEAN_AVERAGING = 0x1,
	MEDIAN_AVERAGING = 0x2,
};

enum meson_sar_adc_num_samples {
	ONE_SAMPLE = 0x0,
	TWO_SAMPLES = 0x1,
	FOUR_SAMPLES = 0x2,
	EIGHT_SAMPLES = 0x3,
};

enum meson_sar_adc_chan7_mux_sel {
	CHAN7_MUX_VSS = 0x0,
	CHAN7_MUX_VDD_DIV4 = 0x1,
	CHAN7_MUX_VDD_DIV2 = 0x2,
	CHAN7_MUX_VDD_MUL3_DIV4 = 0x3,
	CHAN7_MUX_VDD = 0x4,
	CHAN7_MUX_CH7_INPUT = 0x7,
};

struct meson_sar_adc_data {
	bool					has_bl30_integration;
	unsigned int				resolution;
	const char				*name;
};

struct meson_sar_adc_priv {
	struct regmap				*regmap;
	struct regulator			*vref;
	const struct meson_sar_adc_data		*data;
	struct clk				*clkin;
	struct clk				*core_clk;
	struct clk				*sana_clk;
	struct clk				*adc_sel_clk;
	struct clk				*adc_clk;
	struct clk_gate				clk_gate;
	struct clk				*adc_div_clk;
	struct clk_divider			clk_div;
	struct completion			done;
	int					calibbias;
	int					calibscale;
};

static const struct regmap_config meson_sar_adc_regmap_config = {
	.reg_bits = 8,
	.val_bits = 32,
	.reg_stride = 4,
	.max_register = MESON_SAR_ADC_REG13,
};

static unsigned int meson_sar_adc_get_fifo_count(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	u32 regval;

	regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);

	return FIELD_GET(MESON_SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
}

static int meson_sar_adc_calib_val(struct iio_dev *indio_dev, int val)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int tmp;

	/* use val_calib = scale * val_raw + offset calibration function */
	tmp = div_s64((s64)val * priv->calibscale, MILLION) + priv->calibbias;

	return clamp(tmp, 0, (1 << priv->data->resolution) - 1);
}

static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int regval, timeout = 10000;

	/*
	 * NOTE: we need a small delay before reading the status, otherwise
	 * the sample engine may not have started internally (which would
	 * seem to us that sampling is already finished).
	 */
	do {
		udelay(1);
		regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
	} while (FIELD_GET(MESON_SAR_ADC_REG0_BUSY_MASK, regval) && timeout--);

	if (timeout < 0)
		return -ETIMEDOUT;

	return 0;
}

static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
					 const struct iio_chan_spec *chan,
					 int *val)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int regval, fifo_chan, fifo_val, count;

	if(!wait_for_completion_timeout(&priv->done,
				msecs_to_jiffies(MESON_SAR_ADC_TIMEOUT)))
		return -ETIMEDOUT;

	count = meson_sar_adc_get_fifo_count(indio_dev);
	if (count != 1) {
		dev_err(&indio_dev->dev,
			"ADC FIFO has %d element(s) instead of one\n", count);
		return -EINVAL;
	}

	regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &regval);
	fifo_chan = FIELD_GET(MESON_SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
	if (fifo_chan != chan->channel) {
		dev_err(&indio_dev->dev,
			"ADC FIFO entry belongs to channel %d instead of %d\n",
			fifo_chan, chan->channel);
		return -EINVAL;
	}

	fifo_val = FIELD_GET(MESON_SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK, regval);
	fifo_val &= GENMASK(priv->data->resolution - 1, 0);
	*val = meson_sar_adc_calib_val(indio_dev, fifo_val);

	return 0;
}

static void meson_sar_adc_set_averaging(struct iio_dev *indio_dev,
					const struct iio_chan_spec *chan,
					enum meson_sar_adc_avg_mode mode,
					enum meson_sar_adc_num_samples samples)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int val, channel = chan->channel;

	val = samples << MESON_SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(channel);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_AVG_CNTL,
			   MESON_SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(channel),
			   val);

	val = mode << MESON_SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(channel);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_AVG_CNTL,
			   MESON_SAR_ADC_AVG_CNTL_AVG_MODE_MASK(channel), val);
}

static void meson_sar_adc_enable_channel(struct iio_dev *indio_dev,
					const struct iio_chan_spec *chan)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	u32 regval;

	/*
	 * the SAR ADC engine allows sampling multiple channels at the same
	 * time. to keep it simple we're only working with one *internal*
	 * channel, which starts counting at index 0 (which means: count = 1).
	 */
	regval = FIELD_PREP(MESON_SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, 0);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_CHAN_LIST,
			   MESON_SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, regval);

	/* map channel index 0 to the channel which we want to read */
	regval = FIELD_PREP(MESON_SAR_ADC_CHAN_LIST_ENTRY_MASK(0),
			    chan->channel);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_CHAN_LIST,
			   MESON_SAR_ADC_CHAN_LIST_ENTRY_MASK(0), regval);

	regval = FIELD_PREP(MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_MUX_MASK,
			    chan->channel);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DETECT_IDLE_SW,
			   MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_MUX_MASK,
			   regval);

	regval = FIELD_PREP(MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_MUX_SEL_MASK,
			    chan->channel);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DETECT_IDLE_SW,
			   MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_MUX_SEL_MASK,
			   regval);

	if (chan->channel == 6)
		regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELTA_10,
				   MESON_SAR_ADC_DELTA_10_TEMP_SEL, 0);
}

static void meson_sar_adc_set_chan7_mux(struct iio_dev *indio_dev,
					enum meson_sar_adc_chan7_mux_sel sel)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	u32 regval;

	regval = FIELD_PREP(MESON_SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, sel);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
			   MESON_SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, regval);

	usleep_range(10, 20);
}

static void meson_sar_adc_start_sample_engine(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);

	reinit_completion(&priv->done);

	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
			   MESON_SAR_ADC_REG0_FIFO_IRQ_EN,
			   MESON_SAR_ADC_REG0_FIFO_IRQ_EN);

	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
			   MESON_SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE,
			   MESON_SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE);

	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
			   MESON_SAR_ADC_REG0_SAMPLING_START,
			   MESON_SAR_ADC_REG0_SAMPLING_START);
}

static void meson_sar_adc_stop_sample_engine(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);

	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
			   MESON_SAR_ADC_REG0_FIFO_IRQ_EN, 0);

	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
			   MESON_SAR_ADC_REG0_SAMPLING_STOP,
			   MESON_SAR_ADC_REG0_SAMPLING_STOP);

	/* wait until all modules are stopped */
	meson_sar_adc_wait_busy_clear(indio_dev);

	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
			   MESON_SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE, 0);
}

static int meson_sar_adc_lock(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int val, timeout = 10000;

	mutex_lock(&indio_dev->mlock);

	if (priv->data->has_bl30_integration) {
		/* prevent BL30 from using the SAR ADC while we are using it */
		regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
				MESON_SAR_ADC_DELAY_KERNEL_BUSY,
				MESON_SAR_ADC_DELAY_KERNEL_BUSY);

		/*
		 * wait until BL30 releases it's lock (so we can use the SAR
		 * ADC)
		 */
		do {
			udelay(1);
			regmap_read(priv->regmap, MESON_SAR_ADC_DELAY, &val);
		} while (val & MESON_SAR_ADC_DELAY_BL30_BUSY && timeout--);

		if (timeout < 0)
			return -ETIMEDOUT;
	}

	return 0;
}

static void meson_sar_adc_unlock(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);

	if (priv->data->has_bl30_integration)
		/* allow BL30 to use the SAR ADC again */
		regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
				MESON_SAR_ADC_DELAY_KERNEL_BUSY, 0);

	mutex_unlock(&indio_dev->mlock);
}

static void meson_sar_adc_clear_fifo(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	unsigned int count, tmp;

	for (count = 0; count < MESON_SAR_ADC_MAX_FIFO_SIZE; count++) {
		if (!meson_sar_adc_get_fifo_count(indio_dev))
			break;

		regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &tmp);
	}
}

static int meson_sar_adc_get_sample(struct iio_dev *indio_dev,
				    const struct iio_chan_spec *chan,
				    enum meson_sar_adc_avg_mode avg_mode,
				    enum meson_sar_adc_num_samples avg_samples,
				    int *val)
{
	int ret;

	ret = meson_sar_adc_lock(indio_dev);
	if (ret)
		return ret;

	/* clear the FIFO to make sure we're not reading old values */
	meson_sar_adc_clear_fifo(indio_dev);

	meson_sar_adc_set_averaging(indio_dev, chan, avg_mode, avg_samples);

	meson_sar_adc_enable_channel(indio_dev, chan);

	meson_sar_adc_start_sample_engine(indio_dev);
	ret = meson_sar_adc_read_raw_sample(indio_dev, chan, val);
	meson_sar_adc_stop_sample_engine(indio_dev);

	meson_sar_adc_unlock(indio_dev);

	if (ret) {
		dev_warn(indio_dev->dev.parent,
			 "failed to read sample for channel %d: %d\n",
			 chan->channel, ret);
		return ret;
	}

	return IIO_VAL_INT;
}

static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev,
					   const struct iio_chan_spec *chan,
					   int *val, int *val2, long mask)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		return meson_sar_adc_get_sample(indio_dev, chan, NO_AVERAGING,
						ONE_SAMPLE, val);
		break;

	case IIO_CHAN_INFO_AVERAGE_RAW:
		return meson_sar_adc_get_sample(indio_dev, chan,
						MEAN_AVERAGING, EIGHT_SAMPLES,
						val);
		break;

	case IIO_CHAN_INFO_SCALE:
		ret = regulator_get_voltage(priv->vref);
		if (ret < 0) {
			dev_err(indio_dev->dev.parent,
				"failed to get vref voltage: %d\n", ret);
			return ret;
		}

		*val = ret / 1000;
		*val2 = priv->data->resolution;
		return IIO_VAL_FRACTIONAL_LOG2;

	case IIO_CHAN_INFO_CALIBBIAS:
		*val = priv->calibbias;
		return IIO_VAL_INT;

	case IIO_CHAN_INFO_CALIBSCALE:
		*val = priv->calibscale / MILLION;
		*val2 = priv->calibscale % MILLION;
		return IIO_VAL_INT_PLUS_MICRO;

	default:
		return -EINVAL;
	}
}

static int meson_sar_adc_clk_init(struct iio_dev *indio_dev,
				  void __iomem *base)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	struct clk_init_data init;
	const char *clk_parents[1];

	init.name = devm_kasprintf(&indio_dev->dev, GFP_KERNEL, "%pOF#adc_div",
				   indio_dev->dev.of_node);
	init.flags = 0;
	init.ops = &clk_divider_ops;
	clk_parents[0] = __clk_get_name(priv->clkin);
	init.parent_names = clk_parents;
	init.num_parents = 1;

	priv->clk_div.reg = base + MESON_SAR_ADC_REG3;
	priv->clk_div.shift = MESON_SAR_ADC_REG3_ADC_CLK_DIV_SHIFT;
	priv->clk_div.width = MESON_SAR_ADC_REG3_ADC_CLK_DIV_WIDTH;
	priv->clk_div.hw.init = &init;
	priv->clk_div.flags = 0;

	priv->adc_div_clk = devm_clk_register(&indio_dev->dev,
					      &priv->clk_div.hw);
	if (WARN_ON(IS_ERR(priv->adc_div_clk)))
		return PTR_ERR(priv->adc_div_clk);

	init.name = devm_kasprintf(&indio_dev->dev, GFP_KERNEL, "%pOF#adc_en",
				   indio_dev->dev.of_node);
	init.flags = CLK_SET_RATE_PARENT;
	init.ops = &clk_gate_ops;
	clk_parents[0] = __clk_get_name(priv->adc_div_clk);
	init.parent_names = clk_parents;
	init.num_parents = 1;

	priv->clk_gate.reg = base + MESON_SAR_ADC_REG3;
	priv->clk_gate.bit_idx = fls(MESON_SAR_ADC_REG3_CLK_EN);
	priv->clk_gate.hw.init = &init;

	priv->adc_clk = devm_clk_register(&indio_dev->dev, &priv->clk_gate.hw);
	if (WARN_ON(IS_ERR(priv->adc_clk)))
		return PTR_ERR(priv->adc_clk);

	return 0;
}

static int meson_sar_adc_init(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int regval, ret;

	/*
	 * make sure we start at CH7 input since the other muxes are only used
	 * for internal calibration.
	 */
	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_CH7_INPUT);

	if (priv->data->has_bl30_integration) {
		/*
		 * leave sampling delay and the input clocks as configured by
		 * BL30 to make sure BL30 gets the values it expects when
		 * reading the temperature sensor.
		 */
		regmap_read(priv->regmap, MESON_SAR_ADC_REG3, &regval);
		if (regval & MESON_SAR_ADC_REG3_BL30_INITIALIZED)
			return 0;
	}

	meson_sar_adc_stop_sample_engine(indio_dev);

	/* update the channel 6 MUX to select the temperature sensor */
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
			MESON_SAR_ADC_REG0_ADC_TEMP_SEN_SEL,
			MESON_SAR_ADC_REG0_ADC_TEMP_SEN_SEL);

	/* disable all channels by default */
	regmap_write(priv->regmap, MESON_SAR_ADC_CHAN_LIST, 0x0);

	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
			   MESON_SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE, 0);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
			   MESON_SAR_ADC_REG3_CNTL_USE_SC_DLY,
			   MESON_SAR_ADC_REG3_CNTL_USE_SC_DLY);

	/* delay between two samples = (10+1) * 1uS */
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
			   MESON_SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
			   FIELD_PREP(MESON_SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK,
				      10));
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
			   MESON_SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK,
			   FIELD_PREP(MESON_SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK,
				      0));

	/* delay between two samples = (10+1) * 1uS */
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
			   MESON_SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
			   FIELD_PREP(MESON_SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
				      10));
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
			   MESON_SAR_ADC_DELAY_INPUT_DLY_SEL_MASK,
			   FIELD_PREP(MESON_SAR_ADC_DELAY_INPUT_DLY_SEL_MASK,
				      1));

	ret = clk_set_parent(priv->adc_sel_clk, priv->clkin);
	if (ret) {
		dev_err(indio_dev->dev.parent,
			"failed to set adc parent to clkin\n");
		return ret;
	}

	ret = clk_set_rate(priv->adc_clk, 1200000);
	if (ret) {
		dev_err(indio_dev->dev.parent,
			"failed to set adc clock rate\n");
		return ret;
	}

	return 0;
}

static int meson_sar_adc_hw_enable(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int ret;
	u32 regval;

	ret = meson_sar_adc_lock(indio_dev);
	if (ret)
		goto err_lock;

	ret = regulator_enable(priv->vref);
	if (ret < 0) {
		dev_err(indio_dev->dev.parent,
			"failed to enable vref regulator\n");
		goto err_vref;
	}

	ret = clk_prepare_enable(priv->core_clk);
	if (ret) {
		dev_err(indio_dev->dev.parent, "failed to enable core clk\n");
		goto err_core_clk;
	}

	ret = clk_prepare_enable(priv->sana_clk);
	if (ret) {
		dev_err(indio_dev->dev.parent, "failed to enable sana clk\n");
		goto err_sana_clk;
	}

	regval = FIELD_PREP(MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, 1);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
			   MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, regval);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG11,
			   MESON_SAR_ADC_REG11_BANDGAP_EN,
			   MESON_SAR_ADC_REG11_BANDGAP_EN);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
			   MESON_SAR_ADC_REG3_ADC_EN,
			   MESON_SAR_ADC_REG3_ADC_EN);

	udelay(5);

	ret = clk_prepare_enable(priv->adc_clk);
	if (ret) {
		dev_err(indio_dev->dev.parent, "failed to enable adc clk\n");
		goto err_adc_clk;
	}

	meson_sar_adc_unlock(indio_dev);

	return 0;

err_adc_clk:
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
			   MESON_SAR_ADC_REG3_ADC_EN, 0);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG11,
			   MESON_SAR_ADC_REG11_BANDGAP_EN, 0);
	clk_disable_unprepare(priv->sana_clk);
err_sana_clk:
	clk_disable_unprepare(priv->core_clk);
err_core_clk:
	regulator_disable(priv->vref);
err_vref:
	meson_sar_adc_unlock(indio_dev);
err_lock:
	return ret;
}

static int meson_sar_adc_hw_disable(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int ret;

	ret = meson_sar_adc_lock(indio_dev);
	if (ret)
		return ret;

	clk_disable_unprepare(priv->adc_clk);

	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
			   MESON_SAR_ADC_REG3_ADC_EN, 0);
	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG11,
			   MESON_SAR_ADC_REG11_BANDGAP_EN, 0);

	clk_disable_unprepare(priv->sana_clk);
	clk_disable_unprepare(priv->core_clk);

	regulator_disable(priv->vref);

	meson_sar_adc_unlock(indio_dev);

	return 0;
}

static irqreturn_t meson_sar_adc_irq(int irq, void *data)
{
	struct iio_dev *indio_dev = data;
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	unsigned int cnt, threshold;
	u32 regval;

	regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
	cnt = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
	threshold = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, regval);

	if (cnt < threshold)
		return IRQ_NONE;

	complete(&priv->done);

	return IRQ_HANDLED;
}

static int meson_sar_adc_calib(struct iio_dev *indio_dev)
{
	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
	int ret, nominal0, nominal1, value0, value1;

	/* use points 25% and 75% for calibration */
	nominal0 = (1 << priv->data->resolution) / 4;
	nominal1 = (1 << priv->data->resolution) * 3 / 4;

	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_DIV4);
	usleep_range(10, 20);
	ret = meson_sar_adc_get_sample(indio_dev,
				       &meson_sar_adc_iio_channels[7],
				       MEAN_AVERAGING, EIGHT_SAMPLES, &value0);
	if (ret < 0)
		goto out;

	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_MUL3_DIV4);
	usleep_range(10, 20);
	ret = meson_sar_adc_get_sample(indio_dev,
				       &meson_sar_adc_iio_channels[7],
				       MEAN_AVERAGING, EIGHT_SAMPLES, &value1);
	if (ret < 0)
		goto out;

	if (value1 <= value0) {
		ret = -EINVAL;
		goto out;
	}

	priv->calibscale = div_s64((nominal1 - nominal0) * (s64)MILLION,
				   value1 - value0);
	priv->calibbias = nominal0 - div_s64((s64)value0 * priv->calibscale,
					     MILLION);
	ret = 0;
out:
	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_CH7_INPUT);

	return ret;
}

static const struct iio_info meson_sar_adc_iio_info = {
	.read_raw = meson_sar_adc_iio_info_read_raw,
	.driver_module = THIS_MODULE,
};

static const struct meson_sar_adc_data meson_sar_adc_meson8_data = {
	.has_bl30_integration = false,
	.resolution = 10,
	.name = "meson-meson8-saradc",
};

static const struct meson_sar_adc_data meson_sar_adc_meson8b_data = {
	.has_bl30_integration = false,
	.resolution = 10,
	.name = "meson-meson8b-saradc",
};

static const struct meson_sar_adc_data meson_sar_adc_gxbb_data = {
	.has_bl30_integration = true,
	.resolution = 10,
	.name = "meson-gxbb-saradc",
};

static const struct meson_sar_adc_data meson_sar_adc_gxl_data = {
	.has_bl30_integration = true,
	.resolution = 12,
	.name = "meson-gxl-saradc",
};

static const struct meson_sar_adc_data meson_sar_adc_gxm_data = {
	.has_bl30_integration = true,
	.resolution = 12,
	.name = "meson-gxm-saradc",
};

static const struct of_device_id meson_sar_adc_of_match[] = {
	{
		.compatible = "amlogic,meson8-saradc",
		.data = &meson_sar_adc_meson8_data,
	},
	{
		.compatible = "amlogic,meson8b-saradc",
		.data = &meson_sar_adc_meson8b_data,
	},
	{
		.compatible = "amlogic,meson-gxbb-saradc",
		.data = &meson_sar_adc_gxbb_data,
	}, {
		.compatible = "amlogic,meson-gxl-saradc",
		.data = &meson_sar_adc_gxl_data,
	}, {
		.compatible = "amlogic,meson-gxm-saradc",
		.data = &meson_sar_adc_gxm_data,
	},
	{},
};
MODULE_DEVICE_TABLE(of, meson_sar_adc_of_match);

static int meson_sar_adc_probe(struct platform_device *pdev)
{
	struct meson_sar_adc_priv *priv;
	struct iio_dev *indio_dev;
	struct resource *res;
	void __iomem *base;
	const struct of_device_id *match;
	int irq, ret;

	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
	if (!indio_dev) {
		dev_err(&pdev->dev, "failed allocating iio device\n");
		return -ENOMEM;
	}

	priv = iio_priv(indio_dev);
	init_completion(&priv->done);

	match = of_match_device(meson_sar_adc_of_match, &pdev->dev);
	if (!match) {
		dev_err(&pdev->dev, "failed to match device\n");
		return -ENODEV;
	}

	priv->data = match->data;

	indio_dev->name = priv->data->name;
	indio_dev->dev.parent = &pdev->dev;
	indio_dev->dev.of_node = pdev->dev.of_node;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->info = &meson_sar_adc_iio_info;

	indio_dev->channels = meson_sar_adc_iio_channels;
	indio_dev->num_channels = ARRAY_SIZE(meson_sar_adc_iio_channels);

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

	irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
	if (!irq)
		return -EINVAL;

	ret = devm_request_irq(&pdev->dev, irq, meson_sar_adc_irq, IRQF_SHARED,
			       dev_name(&pdev->dev), indio_dev);
	if (ret)
		return ret;

	priv->regmap = devm_regmap_init_mmio(&pdev->dev, base,
					     &meson_sar_adc_regmap_config);
	if (IS_ERR(priv->regmap))
		return PTR_ERR(priv->regmap);

	priv->clkin = devm_clk_get(&pdev->dev, "clkin");
	if (IS_ERR(priv->clkin)) {
		dev_err(&pdev->dev, "failed to get clkin\n");
		return PTR_ERR(priv->clkin);
	}

	priv->core_clk = devm_clk_get(&pdev->dev, "core");
	if (IS_ERR(priv->core_clk)) {
		dev_err(&pdev->dev, "failed to get core clk\n");
		return PTR_ERR(priv->core_clk);
	}

	priv->sana_clk = devm_clk_get(&pdev->dev, "sana");
	if (IS_ERR(priv->sana_clk)) {
		if (PTR_ERR(priv->sana_clk) == -ENOENT) {
			priv->sana_clk = NULL;
		} else {
			dev_err(&pdev->dev, "failed to get sana clk\n");
			return PTR_ERR(priv->sana_clk);
		}
	}

	priv->adc_clk = devm_clk_get(&pdev->dev, "adc_clk");
	if (IS_ERR(priv->adc_clk)) {
		if (PTR_ERR(priv->adc_clk) == -ENOENT) {
			priv->adc_clk = NULL;
		} else {
			dev_err(&pdev->dev, "failed to get adc clk\n");
			return PTR_ERR(priv->adc_clk);
		}
	}

	priv->adc_sel_clk = devm_clk_get(&pdev->dev, "adc_sel");
	if (IS_ERR(priv->adc_sel_clk)) {
		if (PTR_ERR(priv->adc_sel_clk) == -ENOENT) {
			priv->adc_sel_clk = NULL;
		} else {
			dev_err(&pdev->dev, "failed to get adc_sel clk\n");
			return PTR_ERR(priv->adc_sel_clk);
		}
	}

	/* on pre-GXBB SoCs the SAR ADC itself provides the ADC clock: */
	if (!priv->adc_clk) {
		ret = meson_sar_adc_clk_init(indio_dev, base);
		if (ret)
			return ret;
	}

	priv->vref = devm_regulator_get(&pdev->dev, "vref");
	if (IS_ERR(priv->vref)) {
		dev_err(&pdev->dev, "failed to get vref regulator\n");
		return PTR_ERR(priv->vref);
	}

	priv->calibscale = MILLION;

	ret = meson_sar_adc_init(indio_dev);
	if (ret)
		goto err;

	ret = meson_sar_adc_hw_enable(indio_dev);
	if (ret)
		goto err;

	ret = meson_sar_adc_calib(indio_dev);
	if (ret)
		dev_warn(&pdev->dev, "calibration failed\n");

	platform_set_drvdata(pdev, indio_dev);

	ret = iio_device_register(indio_dev);
	if (ret)
		goto err_hw;

	return 0;

err_hw:
	meson_sar_adc_hw_disable(indio_dev);
err:
	return ret;
}

static int meson_sar_adc_remove(struct platform_device *pdev)
{
	struct iio_dev *indio_dev = platform_get_drvdata(pdev);

	iio_device_unregister(indio_dev);

	return meson_sar_adc_hw_disable(indio_dev);
}

static int __maybe_unused meson_sar_adc_suspend(struct device *dev)
{
	struct iio_dev *indio_dev = dev_get_drvdata(dev);

	return meson_sar_adc_hw_disable(indio_dev);
}

static int __maybe_unused meson_sar_adc_resume(struct device *dev)
{
	struct iio_dev *indio_dev = dev_get_drvdata(dev);

	return meson_sar_adc_hw_enable(indio_dev);
}

static SIMPLE_DEV_PM_OPS(meson_sar_adc_pm_ops,
			 meson_sar_adc_suspend, meson_sar_adc_resume);

static struct platform_driver meson_sar_adc_driver = {
	.probe		= meson_sar_adc_probe,
	.remove		= meson_sar_adc_remove,
	.driver		= {
		.name	= "meson-saradc",
		.of_match_table = meson_sar_adc_of_match,
		.pm = &meson_sar_adc_pm_ops,
	},
};

module_platform_driver(meson_sar_adc_driver);

MODULE_AUTHOR("Martin Blumenstingl <martin.blumenstingl@googlemail.com>");
MODULE_DESCRIPTION("Amlogic Meson SAR ADC driver");
MODULE_LICENSE("GPL v2");