// SPDX-License-Identifier: GPL-2.0
/*
 * LTC2688 16 channel, 16 bit Voltage Output SoftSpan DAC driver
 *
 * Copyright 2022 Analog Devices Inc.
 */
#include <linux/bitfield.h>
#include <linux/bits.h>
#include <linux/cleanup.h>
#include <linux/clk.h>
#include <linux/device.h>
#include <linux/gpio/consumer.h>
#include <linux/iio/iio.h>
#include <linux/limits.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/property.h>
#include <linux/regmap.h>
#include <linux/regulator/consumer.h>
#include <linux/spi/spi.h>

#define LTC2688_DAC_CHANNELS			16

#define LTC2688_CMD_CH_CODE(x)			(0x00 + (x))
#define LTC2688_CMD_CH_SETTING(x)		(0x10 + (x))
#define LTC2688_CMD_CH_OFFSET(x)		(0X20 + (x))
#define LTC2688_CMD_CH_GAIN(x)			(0x30 + (x))
#define LTC2688_CMD_CH_CODE_UPDATE(x)		(0x40 + (x))

#define LTC2688_CMD_CONFIG			0x70
#define LTC2688_CMD_POWERDOWN			0x71
#define LTC2688_CMD_A_B_SELECT			0x72
#define LTC2688_CMD_SW_TOGGLE			0x73
#define LTC2688_CMD_TOGGLE_DITHER_EN		0x74
#define LTC2688_CMD_THERMAL_STAT		0x77
#define LTC2688_CMD_UPDATE_ALL			0x7C
#define LTC2688_CMD_NOOP			0xFF

#define LTC2688_READ_OPERATION			0x80

/* Channel Settings */
#define LTC2688_CH_SPAN_MSK			GENMASK(2, 0)
#define LTC2688_CH_OVERRANGE_MSK		BIT(3)
#define LTC2688_CH_TD_SEL_MSK			GENMASK(5, 4)
#define LTC2688_CH_TGP_MAX			3
#define LTC2688_CH_DIT_PER_MSK			GENMASK(8, 6)
#define LTC2688_CH_DIT_PH_MSK			GENMASK(10, 9)
#define LTC2688_CH_MODE_MSK			BIT(11)

#define LTC2688_DITHER_RAW_MASK			GENMASK(15, 2)
#define LTC2688_CH_CALIBBIAS_MASK		GENMASK(15, 2)
#define LTC2688_DITHER_RAW_MAX_VAL		(BIT(14) - 1)
#define LTC2688_CH_CALIBBIAS_MAX_VAL		(BIT(14) - 1)

/* Configuration register */
#define LTC2688_CONFIG_RST			BIT(15)
#define LTC2688_CONFIG_EXT_REF			BIT(1)

#define LTC2688_DITHER_FREQ_AVAIL_N		5

enum {
	LTC2688_SPAN_RANGE_0V_5V,
	LTC2688_SPAN_RANGE_0V_10V,
	LTC2688_SPAN_RANGE_M5V_5V,
	LTC2688_SPAN_RANGE_M10V_10V,
	LTC2688_SPAN_RANGE_M15V_15V,
	LTC2688_SPAN_RANGE_MAX
};

enum {
	LTC2688_MODE_DEFAULT,
	LTC2688_MODE_DITHER_TOGGLE,
};

struct ltc2688_chan {
	long dither_frequency[LTC2688_DITHER_FREQ_AVAIL_N];
	bool overrange;
	bool toggle_chan;
	u8 mode;
};

struct ltc2688_state {
	struct spi_device *spi;
	struct regmap *regmap;
	struct ltc2688_chan channels[LTC2688_DAC_CHANNELS];
	struct iio_chan_spec *iio_chan;
	/* lock to protect against multiple access to the device and shared data */
	struct mutex lock;
	int vref;
	/*
	 * DMA (thus cache coherency maintenance) may require the
	 * transfer buffers to live in their own cache lines.
	 */
	u8 tx_data[6] __aligned(IIO_DMA_MINALIGN);
	u8 rx_data[3];
};

static int ltc2688_spi_read(void *context, const void *reg, size_t reg_size,
			    void *val, size_t val_size)
{
	struct ltc2688_state *st = context;
	struct spi_transfer xfers[] = {
		{
			.tx_buf = st->tx_data,
			.len = reg_size + val_size,
			.cs_change = 1,
		}, {
			.tx_buf = st->tx_data + 3,
			.rx_buf = st->rx_data,
			.len = reg_size + val_size,
		},
	};
	int ret;

	memcpy(st->tx_data, reg, reg_size);

	ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
	if (ret)
		return ret;

	memcpy(val, &st->rx_data[1], val_size);

	return 0;
}

static int ltc2688_spi_write(void *context, const void *data, size_t count)
{
	struct ltc2688_state *st = context;

	return spi_write(st->spi, data, count);
}

static int ltc2688_span_get(const struct ltc2688_state *st, int c)
{
	int ret, reg, span;

	ret = regmap_read(st->regmap, LTC2688_CMD_CH_SETTING(c), &reg);
	if (ret)
		return ret;

	span = FIELD_GET(LTC2688_CH_SPAN_MSK, reg);
	/* sanity check to make sure we don't get any weird value from the HW */
	if (span >= LTC2688_SPAN_RANGE_MAX)
		return -EIO;

	return span;
}

static const int ltc2688_span_helper[LTC2688_SPAN_RANGE_MAX][2] = {
	{0, 5000}, {0, 10000}, {-5000, 5000}, {-10000, 10000}, {-15000, 15000},
};

static int ltc2688_scale_get(const struct ltc2688_state *st, int c, int *val)
{
	const struct ltc2688_chan *chan = &st->channels[c];
	int span, fs;

	span = ltc2688_span_get(st, c);
	if (span < 0)
		return span;

	fs = ltc2688_span_helper[span][1] - ltc2688_span_helper[span][0];
	if (chan->overrange)
		fs = mult_frac(fs, 105, 100);

	*val = DIV_ROUND_CLOSEST(fs * st->vref, 4096);

	return 0;
}

static int ltc2688_offset_get(const struct ltc2688_state *st, int c, int *val)
{
	int span;

	span = ltc2688_span_get(st, c);
	if (span < 0)
		return span;

	if (ltc2688_span_helper[span][0] < 0)
		*val = -32768;
	else
		*val = 0;

	return 0;
}

enum {
	LTC2688_INPUT_A,
	LTC2688_INPUT_B,
	LTC2688_INPUT_B_AVAIL,
	LTC2688_DITHER_OFF,
	LTC2688_DITHER_FREQ_AVAIL,
};

static int ltc2688_dac_code_write(struct ltc2688_state *st, u32 chan, u32 input,
				  u16 code)
{
	struct ltc2688_chan *c = &st->channels[chan];
	int ret, reg;

	/* 2 LSBs set to 0 if writing dither amplitude */
	if (!c->toggle_chan && input == LTC2688_INPUT_B) {
		if (code > LTC2688_DITHER_RAW_MAX_VAL)
			return -EINVAL;

		code = FIELD_PREP(LTC2688_DITHER_RAW_MASK, code);
	}

	guard(mutex)(&st->lock);
	/* select the correct input register to read from */
	ret = regmap_update_bits(st->regmap, LTC2688_CMD_A_B_SELECT, BIT(chan),
				 input << chan);
	if (ret)
		return ret;

	/*
	 * If in dither/toggle mode the dac should be updated by an
	 * external signal (or sw toggle) and not here.
	 */
	if (c->mode == LTC2688_MODE_DEFAULT)
		reg = LTC2688_CMD_CH_CODE_UPDATE(chan);
	else
		reg = LTC2688_CMD_CH_CODE(chan);

	return regmap_write(st->regmap, reg, code);
}

static int ltc2688_dac_code_read(struct ltc2688_state *st, u32 chan, u32 input,
				 u32 *code)
{
	struct ltc2688_chan *c = &st->channels[chan];
	int ret;

	guard(mutex)(&st->lock);
	ret = regmap_update_bits(st->regmap, LTC2688_CMD_A_B_SELECT, BIT(chan),
				 input << chan);
	if (ret)
		return ret;

	ret = regmap_read(st->regmap, LTC2688_CMD_CH_CODE(chan), code);
	if (ret)
		return ret;

	if (!c->toggle_chan && input == LTC2688_INPUT_B)
		*code = FIELD_GET(LTC2688_DITHER_RAW_MASK, *code);

	return 0;
}

static const int ltc2688_raw_range[] = {0, 1, U16_MAX};

static int ltc2688_read_avail(struct iio_dev *indio_dev,
			      struct iio_chan_spec const *chan,
			      const int **vals, int *type, int *length,
			      long info)
{
	switch (info) {
	case IIO_CHAN_INFO_RAW:
		*vals = ltc2688_raw_range;
		*type = IIO_VAL_INT;
		return IIO_AVAIL_RANGE;
	default:
		return -EINVAL;
	}
}

static int ltc2688_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan, int *val,
			    int *val2, long info)
{
	struct ltc2688_state *st = iio_priv(indio_dev);
	int ret;

	switch (info) {
	case IIO_CHAN_INFO_RAW:
		ret = ltc2688_dac_code_read(st, chan->channel, LTC2688_INPUT_A,
					    val);
		if (ret)
			return ret;

		return IIO_VAL_INT;
	case IIO_CHAN_INFO_OFFSET:
		ret = ltc2688_offset_get(st, chan->channel, val);
		if (ret)
			return ret;

		return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
		ret = ltc2688_scale_get(st, chan->channel, val);
		if (ret)
			return ret;

		*val2 = 16;
		return IIO_VAL_FRACTIONAL_LOG2;
	case IIO_CHAN_INFO_CALIBBIAS:
		ret = regmap_read(st->regmap,
				  LTC2688_CMD_CH_OFFSET(chan->channel), val);
		if (ret)
			return ret;

		*val = FIELD_GET(LTC2688_CH_CALIBBIAS_MASK, *val);
		return IIO_VAL_INT;
	case IIO_CHAN_INFO_CALIBSCALE:
		ret = regmap_read(st->regmap,
				  LTC2688_CMD_CH_GAIN(chan->channel), val);
		if (ret)
			return ret;

		return IIO_VAL_INT;
	default:
		return -EINVAL;
	}
}

static int ltc2688_write_raw(struct iio_dev *indio_dev,
			     struct iio_chan_spec const *chan, int val,
			     int val2, long info)
{
	struct ltc2688_state *st = iio_priv(indio_dev);

	switch (info) {
	case IIO_CHAN_INFO_RAW:
		if (val > U16_MAX || val < 0)
			return -EINVAL;

		return ltc2688_dac_code_write(st, chan->channel,
					      LTC2688_INPUT_A, val);
	case IIO_CHAN_INFO_CALIBBIAS:
		if (val > LTC2688_CH_CALIBBIAS_MAX_VAL)
			return -EINVAL;

		return regmap_write(st->regmap,
				    LTC2688_CMD_CH_OFFSET(chan->channel),
				    FIELD_PREP(LTC2688_CH_CALIBBIAS_MASK, val));
	case IIO_CHAN_INFO_CALIBSCALE:
		return regmap_write(st->regmap,
				    LTC2688_CMD_CH_GAIN(chan->channel), val);
	default:
		return -EINVAL;
	}
}

static ssize_t ltc2688_dither_toggle_set(struct iio_dev *indio_dev,
					 uintptr_t private,
					 const struct iio_chan_spec *chan,
					 const char *buf, size_t len)
{
	struct ltc2688_state *st = iio_priv(indio_dev);
	struct ltc2688_chan *c = &st->channels[chan->channel];
	int ret;
	bool en;

	ret = kstrtobool(buf, &en);
	if (ret)
		return ret;

	guard(mutex)(&st->lock);
	ret = regmap_update_bits(st->regmap, LTC2688_CMD_TOGGLE_DITHER_EN,
				 BIT(chan->channel), en << chan->channel);
	if (ret)
		return ret;

	c->mode = en ? LTC2688_MODE_DITHER_TOGGLE : LTC2688_MODE_DEFAULT;

	return len;
}

static ssize_t ltc2688_reg_bool_get(struct iio_dev *indio_dev,
				    uintptr_t private,
				    const struct iio_chan_spec *chan,
				    char *buf)
{
	const struct ltc2688_state *st = iio_priv(indio_dev);
	int ret;
	u32 val;

	ret = regmap_read(st->regmap, private, &val);
	if (ret)
		return ret;

	return sysfs_emit(buf, "%u\n", !!(val & BIT(chan->channel)));
}

static ssize_t ltc2688_reg_bool_set(struct iio_dev *indio_dev,
				    uintptr_t private,
				    const struct iio_chan_spec *chan,
				    const char *buf, size_t len)
{
	const struct ltc2688_state *st = iio_priv(indio_dev);
	int ret;
	bool en;

	ret = kstrtobool(buf, &en);
	if (ret)
		return ret;

	ret = regmap_update_bits(st->regmap, private, BIT(chan->channel),
				 en << chan->channel);
	if (ret)
		return ret;

	return len;
}

static ssize_t ltc2688_dither_freq_avail(const struct ltc2688_state *st,
					 const struct ltc2688_chan *chan,
					 char *buf)
{
	int sz = 0;
	u32 f;

	for (f = 0; f < ARRAY_SIZE(chan->dither_frequency); f++)
		sz += sysfs_emit_at(buf, sz, "%ld ", chan->dither_frequency[f]);

	buf[sz - 1] = '\n';

	return sz;
}

static ssize_t ltc2688_dither_freq_get(struct iio_dev *indio_dev,
				       uintptr_t private,
				       const struct iio_chan_spec *chan,
				       char *buf)
{
	const struct ltc2688_state *st = iio_priv(indio_dev);
	const struct ltc2688_chan *c = &st->channels[chan->channel];
	u32 reg, freq;
	int ret;

	if (private == LTC2688_DITHER_FREQ_AVAIL)
		return ltc2688_dither_freq_avail(st, c, buf);

	ret = regmap_read(st->regmap, LTC2688_CMD_CH_SETTING(chan->channel),
			  &reg);
	if (ret)
		return ret;

	freq = FIELD_GET(LTC2688_CH_DIT_PER_MSK, reg);
	if (freq >= ARRAY_SIZE(c->dither_frequency))
		return -EIO;

	return sysfs_emit(buf, "%ld\n", c->dither_frequency[freq]);
}

static ssize_t ltc2688_dither_freq_set(struct iio_dev *indio_dev,
				       uintptr_t private,
				       const struct iio_chan_spec *chan,
				       const char *buf, size_t len)
{
	const struct ltc2688_state *st = iio_priv(indio_dev);
	const struct ltc2688_chan *c = &st->channels[chan->channel];
	long val;
	u32 freq;
	int ret;

	if (private == LTC2688_DITHER_FREQ_AVAIL)
		return -EINVAL;

	ret = kstrtol(buf, 10, &val);
	if (ret)
		return ret;

	for (freq = 0; freq < ARRAY_SIZE(c->dither_frequency); freq++) {
		if (val == c->dither_frequency[freq])
			break;
	}

	if (freq == ARRAY_SIZE(c->dither_frequency))
		return -EINVAL;

	ret = regmap_update_bits(st->regmap,
				 LTC2688_CMD_CH_SETTING(chan->channel),
				 LTC2688_CH_DIT_PER_MSK,
				 FIELD_PREP(LTC2688_CH_DIT_PER_MSK, freq));
	if (ret)
		return ret;

	return len;
}

static ssize_t ltc2688_dac_input_read(struct iio_dev *indio_dev,
				      uintptr_t private,
				      const struct iio_chan_spec *chan,
				      char *buf)
{
	struct ltc2688_state *st = iio_priv(indio_dev);
	int ret;
	u32 val;

	if (private == LTC2688_INPUT_B_AVAIL)
		return sysfs_emit(buf, "[%u %u %u]\n", ltc2688_raw_range[0],
				  ltc2688_raw_range[1],
				  ltc2688_raw_range[2] / 4);

	if (private == LTC2688_DITHER_OFF)
		return sysfs_emit(buf, "0\n");

	ret = ltc2688_dac_code_read(st, chan->channel, private, &val);
	if (ret)
		return ret;

	return sysfs_emit(buf, "%u\n", val);
}

static ssize_t ltc2688_dac_input_write(struct iio_dev *indio_dev,
				       uintptr_t private,
				       const struct iio_chan_spec *chan,
				       const char *buf, size_t len)
{
	struct ltc2688_state *st = iio_priv(indio_dev);
	int ret;
	u16 val;

	if (private == LTC2688_INPUT_B_AVAIL || private == LTC2688_DITHER_OFF)
		return -EINVAL;

	ret = kstrtou16(buf, 10, &val);
	if (ret)
		return ret;

	ret = ltc2688_dac_code_write(st, chan->channel, private, val);
	if (ret)
		return ret;

	return len;
}

static int ltc2688_get_dither_phase(struct iio_dev *dev,
				    const struct iio_chan_spec *chan)
{
	struct ltc2688_state *st = iio_priv(dev);
	int ret, regval;

	ret = regmap_read(st->regmap, LTC2688_CMD_CH_SETTING(chan->channel),
			  &regval);
	if (ret)
		return ret;

	return FIELD_GET(LTC2688_CH_DIT_PH_MSK, regval);
}

static int ltc2688_set_dither_phase(struct iio_dev *dev,
				    const struct iio_chan_spec *chan,
				    unsigned int phase)
{
	struct ltc2688_state *st = iio_priv(dev);

	return regmap_update_bits(st->regmap,
				  LTC2688_CMD_CH_SETTING(chan->channel),
				  LTC2688_CH_DIT_PH_MSK,
				  FIELD_PREP(LTC2688_CH_DIT_PH_MSK, phase));
}

static int ltc2688_reg_access(struct iio_dev *indio_dev,
			      unsigned int reg,
			      unsigned int writeval,
			      unsigned int *readval)
{
	struct ltc2688_state *st = iio_priv(indio_dev);

	if (readval)
		return regmap_read(st->regmap, reg, readval);

	return regmap_write(st->regmap, reg, writeval);
}

static const char * const ltc2688_dither_phase[] = {
	"0", "1.5708", "3.14159", "4.71239",
};

static const struct iio_enum ltc2688_dither_phase_enum = {
	.items = ltc2688_dither_phase,
	.num_items = ARRAY_SIZE(ltc2688_dither_phase),
	.set = ltc2688_set_dither_phase,
	.get = ltc2688_get_dither_phase,
};

#define LTC2688_CHAN_EXT_INFO(_name, _what, _shared, _read, _write) {	\
	.name = _name,							\
	.read = (_read),						\
	.write = (_write),						\
	.private = (_what),						\
	.shared = (_shared),						\
}

/*
 * For toggle mode we only expose the symbol attr (sw_toggle) in case a TGPx is
 * not provided in dts.
 */
static const struct iio_chan_spec_ext_info ltc2688_toggle_sym_ext_info[] = {
	LTC2688_CHAN_EXT_INFO("raw0", LTC2688_INPUT_A, IIO_SEPARATE,
			      ltc2688_dac_input_read, ltc2688_dac_input_write),
	LTC2688_CHAN_EXT_INFO("raw1", LTC2688_INPUT_B, IIO_SEPARATE,
			      ltc2688_dac_input_read, ltc2688_dac_input_write),
	LTC2688_CHAN_EXT_INFO("toggle_en", LTC2688_CMD_TOGGLE_DITHER_EN,
			      IIO_SEPARATE, ltc2688_reg_bool_get,
			      ltc2688_dither_toggle_set),
	LTC2688_CHAN_EXT_INFO("powerdown", LTC2688_CMD_POWERDOWN, IIO_SEPARATE,
			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
	LTC2688_CHAN_EXT_INFO("symbol", LTC2688_CMD_SW_TOGGLE, IIO_SEPARATE,
			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
	{ }
};

static const struct iio_chan_spec_ext_info ltc2688_toggle_ext_info[] = {
	LTC2688_CHAN_EXT_INFO("raw0", LTC2688_INPUT_A, IIO_SEPARATE,
			      ltc2688_dac_input_read, ltc2688_dac_input_write),
	LTC2688_CHAN_EXT_INFO("raw1", LTC2688_INPUT_B, IIO_SEPARATE,
			      ltc2688_dac_input_read, ltc2688_dac_input_write),
	LTC2688_CHAN_EXT_INFO("toggle_en", LTC2688_CMD_TOGGLE_DITHER_EN,
			      IIO_SEPARATE, ltc2688_reg_bool_get,
			      ltc2688_dither_toggle_set),
	LTC2688_CHAN_EXT_INFO("powerdown", LTC2688_CMD_POWERDOWN, IIO_SEPARATE,
			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
	{ }
};

static const struct iio_chan_spec_ext_info ltc2688_dither_ext_info[] = {
	LTC2688_CHAN_EXT_INFO("dither_raw", LTC2688_INPUT_B, IIO_SEPARATE,
			      ltc2688_dac_input_read, ltc2688_dac_input_write),
	LTC2688_CHAN_EXT_INFO("dither_raw_available", LTC2688_INPUT_B_AVAIL,
			      IIO_SEPARATE, ltc2688_dac_input_read,
			      ltc2688_dac_input_write),
	LTC2688_CHAN_EXT_INFO("dither_offset", LTC2688_DITHER_OFF, IIO_SEPARATE,
			      ltc2688_dac_input_read, ltc2688_dac_input_write),
	/*
	 * Not IIO_ENUM because the available freq needs to be computed at
	 * probe. We could still use it, but it didn't felt much right.
	 */
	LTC2688_CHAN_EXT_INFO("dither_frequency", 0, IIO_SEPARATE,
			      ltc2688_dither_freq_get, ltc2688_dither_freq_set),
	LTC2688_CHAN_EXT_INFO("dither_frequency_available",
			      LTC2688_DITHER_FREQ_AVAIL, IIO_SEPARATE,
			      ltc2688_dither_freq_get, ltc2688_dither_freq_set),
	IIO_ENUM("dither_phase", IIO_SEPARATE, &ltc2688_dither_phase_enum),
	IIO_ENUM_AVAILABLE("dither_phase", IIO_SEPARATE,
			   &ltc2688_dither_phase_enum),
	LTC2688_CHAN_EXT_INFO("dither_en", LTC2688_CMD_TOGGLE_DITHER_EN,
			      IIO_SEPARATE, ltc2688_reg_bool_get,
			      ltc2688_dither_toggle_set),
	LTC2688_CHAN_EXT_INFO("powerdown", LTC2688_CMD_POWERDOWN, IIO_SEPARATE,
			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
	{ }
};

static const struct iio_chan_spec_ext_info ltc2688_ext_info[] = {
	LTC2688_CHAN_EXT_INFO("powerdown", LTC2688_CMD_POWERDOWN, IIO_SEPARATE,
			      ltc2688_reg_bool_get, ltc2688_reg_bool_set),
	{ }
};

#define LTC2688_CHANNEL(_chan) {					\
	.type = IIO_VOLTAGE,						\
	.indexed = 1,							\
	.output = 1,							\
	.channel = (_chan),						\
	.info_mask_separate = BIT(IIO_CHAN_INFO_CALIBSCALE) |		\
		BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET) |	\
		BIT(IIO_CHAN_INFO_CALIBBIAS) | BIT(IIO_CHAN_INFO_RAW),	\
	.info_mask_separate_available = BIT(IIO_CHAN_INFO_RAW),		\
	.ext_info = ltc2688_ext_info,					\
}

static const struct iio_chan_spec ltc2688_channels[] = {
	LTC2688_CHANNEL(0),
	LTC2688_CHANNEL(1),
	LTC2688_CHANNEL(2),
	LTC2688_CHANNEL(3),
	LTC2688_CHANNEL(4),
	LTC2688_CHANNEL(5),
	LTC2688_CHANNEL(6),
	LTC2688_CHANNEL(7),
	LTC2688_CHANNEL(8),
	LTC2688_CHANNEL(9),
	LTC2688_CHANNEL(10),
	LTC2688_CHANNEL(11),
	LTC2688_CHANNEL(12),
	LTC2688_CHANNEL(13),
	LTC2688_CHANNEL(14),
	LTC2688_CHANNEL(15),
};

static void ltc2688_clk_disable(void *clk)
{
	clk_disable_unprepare(clk);
}

static const int ltc2688_period[LTC2688_DITHER_FREQ_AVAIL_N] = {
	4, 8, 16, 32, 64,
};

static int ltc2688_tgp_clk_setup(struct ltc2688_state *st,
				 struct ltc2688_chan *chan,
				 struct fwnode_handle *node, int tgp)
{
	struct device *dev = &st->spi->dev;
	unsigned long rate;
	struct clk *clk;
	int ret, f;

	clk = devm_get_clk_from_child(dev, to_of_node(node), NULL);
	if (IS_ERR(clk))
		return dev_err_probe(dev, PTR_ERR(clk), "failed to get tgp clk.\n");

	ret = clk_prepare_enable(clk);
	if (ret)
		return dev_err_probe(dev, ret, "failed to enable tgp clk.\n");

	ret = devm_add_action_or_reset(dev, ltc2688_clk_disable, clk);
	if (ret)
		return ret;

	if (chan->toggle_chan)
		return 0;

	/* calculate available dither frequencies */
	rate = clk_get_rate(clk);
	for (f = 0; f < ARRAY_SIZE(chan->dither_frequency); f++)
		chan->dither_frequency[f] = DIV_ROUND_CLOSEST(rate, ltc2688_period[f]);

	return 0;
}

static int ltc2688_span_lookup(const struct ltc2688_state *st, int min, int max)
{
	u32 span;

	for (span = 0; span < ARRAY_SIZE(ltc2688_span_helper); span++) {
		if (min == ltc2688_span_helper[span][0] &&
		    max == ltc2688_span_helper[span][1])
			return span;
	}

	return -EINVAL;
}

static int ltc2688_channel_config(struct ltc2688_state *st)
{
	struct device *dev = &st->spi->dev;
	u32 reg, clk_input, val, tmp[2];
	int ret, span;

	device_for_each_child_node_scoped(dev, child) {
		struct ltc2688_chan *chan;

		ret = fwnode_property_read_u32(child, "reg", &reg);
		if (ret)
			return dev_err_probe(dev, ret,
					     "Failed to get reg property\n");

		if (reg >= LTC2688_DAC_CHANNELS)
			return dev_err_probe(dev, -EINVAL,
					     "reg bigger than: %d\n",
					     LTC2688_DAC_CHANNELS);

		val = 0;
		chan = &st->channels[reg];
		if (fwnode_property_read_bool(child, "adi,toggle-mode")) {
			chan->toggle_chan = true;
			/* assume sw toggle ABI */
			st->iio_chan[reg].ext_info = ltc2688_toggle_sym_ext_info;
			/*
			 * Clear IIO_CHAN_INFO_RAW bit as toggle channels expose
			 * out_voltage_raw{0|1} files.
			 */
			__clear_bit(IIO_CHAN_INFO_RAW,
				    &st->iio_chan[reg].info_mask_separate);
		}

		ret = fwnode_property_read_u32_array(child, "adi,output-range-microvolt",
						     tmp, ARRAY_SIZE(tmp));
		if (!ret) {
			span = ltc2688_span_lookup(st, (int)tmp[0] / 1000,
						   tmp[1] / 1000);
			if (span < 0)
				return dev_err_probe(dev, span,
						     "output range not valid:[%d %d]\n",
						     tmp[0], tmp[1]);

			val |= FIELD_PREP(LTC2688_CH_SPAN_MSK, span);
		}

		ret = fwnode_property_read_u32(child, "adi,toggle-dither-input",
					       &clk_input);
		if (!ret) {
			if (clk_input >= LTC2688_CH_TGP_MAX) {
				return dev_err_probe(dev, -EINVAL,
						     "toggle-dither-input inv value(%d)\n",
						     clk_input);
			}

			ret = ltc2688_tgp_clk_setup(st, chan, child, clk_input);
			if (ret)
				return ret;

			/*
			 * 0 means software toggle which is the default mode.
			 * Hence the +1.
			 */
			val |= FIELD_PREP(LTC2688_CH_TD_SEL_MSK, clk_input + 1);

			/*
			 * If a TGPx is given, we automatically assume a dither
			 * capable channel (unless toggle is already enabled).
			 * On top of this we just set here the dither bit in the
			 * channel settings. It won't have any effect until the
			 * global toggle/dither bit is enabled.
			 */
			if (!chan->toggle_chan) {
				val |= FIELD_PREP(LTC2688_CH_MODE_MSK, 1);
				st->iio_chan[reg].ext_info = ltc2688_dither_ext_info;
			} else {
				/* wait, no sw toggle after all */
				st->iio_chan[reg].ext_info = ltc2688_toggle_ext_info;
			}
		}

		if (fwnode_property_read_bool(child, "adi,overrange")) {
			chan->overrange = true;
			val |= LTC2688_CH_OVERRANGE_MSK;
		}

		if (!val)
			continue;

		ret = regmap_write(st->regmap, LTC2688_CMD_CH_SETTING(reg),
				   val);
		if (ret)
			return dev_err_probe(dev, ret,
					     "failed to set chan settings\n");
	}

	return 0;
}

static int ltc2688_setup(struct ltc2688_state *st, bool has_external_vref)
{
	struct device *dev = &st->spi->dev;
	struct gpio_desc *gpio;
	int ret;

	/*
	 * If we have a reset pin, use that to reset the board, If not, use
	 * the reset bit.
	 */
	gpio = devm_gpiod_get_optional(dev, "clr", GPIOD_OUT_HIGH);
	if (IS_ERR(gpio))
		return dev_err_probe(dev, PTR_ERR(gpio), "Failed to get reset gpio");
	if (gpio) {
		usleep_range(1000, 1200);
		/* bring device out of reset */
		gpiod_set_value_cansleep(gpio, 0);
	} else {
		ret = regmap_set_bits(st->regmap, LTC2688_CMD_CONFIG,
				      LTC2688_CONFIG_RST);
		if (ret)
			return ret;
	}

	usleep_range(10000, 12000);

	/*
	 * Duplicate the default channel configuration as it can change during
	 * @ltc2688_channel_config()
	 */
	st->iio_chan = devm_kmemdup(dev, ltc2688_channels,
				    sizeof(ltc2688_channels), GFP_KERNEL);
	if (!st->iio_chan)
		return -ENOMEM;

	ret = ltc2688_channel_config(st);
	if (ret)
		return ret;

	if (!has_external_vref)
		return 0;

	return regmap_set_bits(st->regmap, LTC2688_CMD_CONFIG,
			       LTC2688_CONFIG_EXT_REF);
}

static bool ltc2688_reg_readable(struct device *dev, unsigned int reg)
{
	switch (reg) {
	case LTC2688_CMD_CH_CODE(0) ... LTC2688_CMD_CH_GAIN(15):
		return true;
	case LTC2688_CMD_CONFIG ... LTC2688_CMD_THERMAL_STAT:
		return true;
	default:
		return false;
	}
}

static bool ltc2688_reg_writable(struct device *dev, unsigned int reg)
{
	/*
	 * There's a jump from 0x76 to 0x78 in the write codes and the thermal
	 * status code is 0x77 (which is read only) so that we need to check
	 * that special condition.
	 */
	if (reg <= LTC2688_CMD_UPDATE_ALL && reg != LTC2688_CMD_THERMAL_STAT)
		return true;

	return false;
}

static const struct regmap_bus ltc2688_regmap_bus = {
	.read = ltc2688_spi_read,
	.write = ltc2688_spi_write,
	.read_flag_mask = LTC2688_READ_OPERATION,
	.reg_format_endian_default = REGMAP_ENDIAN_BIG,
	.val_format_endian_default = REGMAP_ENDIAN_BIG,
};

static const struct regmap_config ltc2688_regmap_config = {
	.reg_bits = 8,
	.val_bits = 16,
	.readable_reg = ltc2688_reg_readable,
	.writeable_reg = ltc2688_reg_writable,
	/* ignoring the no op command */
	.max_register = LTC2688_CMD_UPDATE_ALL,
};

static const struct iio_info ltc2688_info = {
	.write_raw = ltc2688_write_raw,
	.read_raw = ltc2688_read_raw,
	.read_avail = ltc2688_read_avail,
	.debugfs_reg_access = ltc2688_reg_access,
};

static int ltc2688_probe(struct spi_device *spi)
{
	static const char * const regulators[] = { "vcc", "iovcc" };
	struct ltc2688_state *st;
	struct iio_dev *indio_dev;
	struct device *dev = &spi->dev;
	bool has_external_vref;
	int ret;

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

	st = iio_priv(indio_dev);
	st->spi = spi;

	/* Just write this once. No need to do it in every regmap read. */
	st->tx_data[3] = LTC2688_CMD_NOOP;
	ret = devm_mutex_init(dev, &st->lock);
	if (ret)
		return ret;

	st->regmap = devm_regmap_init(dev, &ltc2688_regmap_bus, st,
				      &ltc2688_regmap_config);
	if (IS_ERR(st->regmap))
		return dev_err_probe(dev, PTR_ERR(st->regmap),
				     "Failed to init regmap");

	ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(regulators),
					     regulators);
	if (ret)
		return dev_err_probe(dev, ret, "Failed to enable regulators\n");

	ret = devm_regulator_get_enable_read_voltage(dev, "vref");
	if (ret < 0 && ret != -ENODEV)
		return dev_err_probe(dev, ret,
				     "Failed to get vref regulator voltage\n");

	has_external_vref = ret != -ENODEV;
	st->vref = has_external_vref ? ret / 1000 : 0;

	ret = ltc2688_setup(st, has_external_vref);
	if (ret)
		return ret;

	indio_dev->name = "ltc2688";
	indio_dev->info = &ltc2688_info;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = st->iio_chan;
	indio_dev->num_channels = ARRAY_SIZE(ltc2688_channels);

	return devm_iio_device_register(dev, indio_dev);
}

static const struct of_device_id ltc2688_of_id[] = {
	{ .compatible = "adi,ltc2688" },
	{ }
};
MODULE_DEVICE_TABLE(of, ltc2688_of_id);

static const struct spi_device_id ltc2688_id[] = {
	{ "ltc2688" },
	{ }
};
MODULE_DEVICE_TABLE(spi, ltc2688_id);

static struct spi_driver ltc2688_driver = {
	.driver = {
		.name = "ltc2688",
		.of_match_table = ltc2688_of_id,
	},
	.probe = ltc2688_probe,
	.id_table = ltc2688_id,
};
module_spi_driver(ltc2688_driver);

MODULE_AUTHOR("Nuno Sá <nuno.sa@analog.com>");
MODULE_DESCRIPTION("Analog Devices LTC2688 DAC");
MODULE_LICENSE("GPL");