path: root/drivers/iio/dac/ltc2688.c

// 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/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,
			.bits_per_word = 8,
			.len = reg_size + val_size,
			.cs_change = 1,
		}, {
			.tx_buf = st->tx_data + 3,
			.rx_buf = st->rx_data,
			.bits_per_word = 8,
			.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)