iio: light: ROHM BU27008 color sensor

The ROHM BU27008 is a sensor with 5 photodiodes (red, green, blue, clear
and IR) with four configurable channels. Red and green being always
available and two out of the rest three (blue, clear, IR) can be
selected to be simultaneously measured. Typical application is adjusting
LCD backlight of TVs, mobile phones and tablet PCs.

Add initial support for the ROHM BU27008 color sensor.
 - raw_read() of RGB and clear channels
 - triggered buffer w/ DRDY interrtupt
Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://lore.kernel.org/r/2594162f0e44148cffb1fb05f1d6edfde6bd11bc.1683541225.git.mazziesaccount@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/Kconfig

@@ -289,6 +289,20 @@ config JSA1212
 	  To compile this driver as a module, choose M here:
 	  the module will be called jsa1212.
 
+config ROHM_BU27008
+	tristate "ROHM BU27008 color (RGB+C/IR) sensor"
+	depends on I2C
+	select REGMAP_I2C
+	select IIO_GTS_HELPER
+	help
+	  Enable support for the ROHM BU27008 color sensor.
+	  The ROHM BU27008 is a sensor with 5 photodiodes (red, green,
+	  blue, clear and IR) with four configurable channels. Red and
+	  green being always available and two out of the rest three
+	  (blue, clear, IR) can be selected to be simultaneously measured.
+	  Typical application is adjusting LCD backlight of TVs,
+	  mobile phones and tablet PCs.
+
 config ROHM_BU27034
 	tristate "ROHM BU27034 ambient light sensor"
 	depends on I2C

drivers/iio/light/Makefile

@@ -39,6 +39,7 @@ obj-$(CONFIG_NOA1305)		+= noa1305.o
 obj-$(CONFIG_OPT3001)		+= opt3001.o
 obj-$(CONFIG_OPT4001)		+= opt4001.o
 obj-$(CONFIG_PA12203001)	+= pa12203001.o
+obj-$(CONFIG_ROHM_BU27008)	+= rohm-bu27008.o
 obj-$(CONFIG_ROHM_BU27034)	+= rohm-bu27034.o
 obj-$(CONFIG_RPR0521)		+= rpr0521.o
 obj-$(CONFIG_SI1133)		+= si1133.o

drivers/iio/light/rohm-bu27008.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * BU27008 ROHM Colour Sensor
+ *
+ * Copyright (c) 2023, ROHM Semiconductor.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/units.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/iio-gts-helper.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+
+#define BU27008_REG_SYSTEM_CONTROL	0x40
+#define BU27008_MASK_SW_RESET		BIT(7)
+#define BU27008_MASK_PART_ID		GENMASK(5, 0)
+#define BU27008_ID			0x1a
+#define BU27008_REG_MODE_CONTROL1	0x41
+#define BU27008_MASK_MEAS_MODE		GENMASK(2, 0)
+#define BU27008_MASK_CHAN_SEL		GENMASK(3, 2)
+
+#define BU27008_REG_MODE_CONTROL2	0x42
+#define BU27008_MASK_RGBC_GAIN		GENMASK(7, 3)
+#define BU27008_MASK_IR_GAIN_LO		GENMASK(2, 0)
+#define BU27008_SHIFT_IR_GAIN		3
+
+#define BU27008_REG_MODE_CONTROL3	0x43
+#define BU27008_MASK_VALID		BIT(7)
+#define BU27008_MASK_INT_EN		BIT(1)
+#define BU27008_INT_EN			BU27008_MASK_INT_EN
+#define BU27008_INT_DIS			0
+#define BU27008_MASK_MEAS_EN		BIT(0)
+#define BU27008_MEAS_EN			BIT(0)
+#define BU27008_MEAS_DIS		0
+
+#define BU27008_REG_DATA0_LO		0x50
+#define BU27008_REG_DATA1_LO		0x52
+#define BU27008_REG_DATA2_LO		0x54
+#define BU27008_REG_DATA3_LO		0x56
+#define BU27008_REG_DATA3_HI		0x57
+#define BU27008_REG_MANUFACTURER_ID	0x92
+#define BU27008_REG_MAX BU27008_REG_MANUFACTURER_ID
+
+/**
+ * enum bu27008_chan_type - BU27008 channel types
+ * @BU27008_RED:	Red channel. Always via data0.
+ * @BU27008_GREEN:	Green channel. Always via data1.
+ * @BU27008_BLUE:	Blue channel. Via data2 (when used).
+ * @BU27008_CLEAR:	Clear channel. Via data2 or data3 (when used).
+ * @BU27008_IR:		IR channel. Via data3 (when used).
+ * @BU27008_NUM_CHANS:	Number of channel types.
+ */
+enum bu27008_chan_type {
+	BU27008_RED,
+	BU27008_GREEN,
+	BU27008_BLUE,
+	BU27008_CLEAR,
+	BU27008_IR,
+	BU27008_NUM_CHANS
+};
+
+/**
+ * enum bu27008_chan - BU27008 physical data channel
+ * @BU27008_DATA0:		Always red.
+ * @BU27008_DATA1:		Always green.
+ * @BU27008_DATA2:		Blue or clear.
+ * @BU27008_DATA3:		IR or clear.
+ * @BU27008_NUM_HW_CHANS:	Number of physical channels
+ */
+enum bu27008_chan {
+	BU27008_DATA0,
+	BU27008_DATA1,
+	BU27008_DATA2,
+	BU27008_DATA3,
+	BU27008_NUM_HW_CHANS
+};
+
+/* We can always measure red and green at same time */
+#define ALWAYS_SCANNABLE (BIT(BU27008_RED) | BIT(BU27008_GREEN))
+
+/* We use these data channel configs. Ensure scan_masks below follow them too */
+#define BU27008_BLUE2_CLEAR3		0x0 /* buffer is R, G, B, C */
+#define BU27008_CLEAR2_IR3		0x1 /* buffer is R, G, C, IR */
+#define BU27008_BLUE2_IR3		0x2 /* buffer is R, G, B, IR */
+
+static const unsigned long bu27008_scan_masks[] = {
+	/* buffer is R, G, B, C */
+	ALWAYS_SCANNABLE | BIT(BU27008_BLUE) | BIT(BU27008_CLEAR),
+	/* buffer is R, G, C, IR */
+	ALWAYS_SCANNABLE | BIT(BU27008_CLEAR) | BIT(BU27008_IR),
+	/* buffer is R, G, B, IR */
+	ALWAYS_SCANNABLE | BIT(BU27008_BLUE) | BIT(BU27008_IR),
+	0
+};
+
+/*
+ * Available scales with gain 1x - 1024x, timings 55, 100, 200, 400 mS
+ * Time impacts to gain: 1x, 2x, 4x, 8x.
+ *
+ * => Max total gain is HWGAIN * gain by integration time (8 * 1024) = 8192
+ *
+ * Max amplification is (HWGAIN * MAX integration-time multiplier) 1024 * 8
+ * = 8192. With NANO scale we get rid of accuracy loss when we start with the
+ * scale 16.0 for HWGAIN1, INT-TIME 55 mS. This way the nano scale for MAX
+ * total gain 8192 will be 1953125
+ */
+#define BU27008_SCALE_1X 16
+
+/* See the data sheet for the "Gain Setting" table */
+#define BU27008_GSEL_1X		0x00
+#define BU27008_GSEL_4X		0x08
+#define BU27008_GSEL_8X		0x09
+#define BU27008_GSEL_16X	0x0a
+#define BU27008_GSEL_32X	0x0b
+#define BU27008_GSEL_64X	0x0c
+#define BU27008_GSEL_256X	0x18
+#define BU27008_GSEL_512X	0x19
+#define BU27008_GSEL_1024X	0x1a
+
+static const struct iio_gain_sel_pair bu27008_gains[] = {
+	GAIN_SCALE_GAIN(1, BU27008_GSEL_1X),
+	GAIN_SCALE_GAIN(4, BU27008_GSEL_4X),
+	GAIN_SCALE_GAIN(8, BU27008_GSEL_8X),
+	GAIN_SCALE_GAIN(16, BU27008_GSEL_16X),
+	GAIN_SCALE_GAIN(32, BU27008_GSEL_32X),
+	GAIN_SCALE_GAIN(64, BU27008_GSEL_64X),
+	GAIN_SCALE_GAIN(256, BU27008_GSEL_256X),
+	GAIN_SCALE_GAIN(512, BU27008_GSEL_512X),
+	GAIN_SCALE_GAIN(1024, BU27008_GSEL_1024X),
+};
+
+static const struct iio_gain_sel_pair bu27008_gains_ir[] = {
+	GAIN_SCALE_GAIN(2, BU27008_GSEL_1X),
+	GAIN_SCALE_GAIN(4, BU27008_GSEL_4X),
+	GAIN_SCALE_GAIN(8, BU27008_GSEL_8X),
+	GAIN_SCALE_GAIN(16, BU27008_GSEL_16X),
+	GAIN_SCALE_GAIN(32, BU27008_GSEL_32X),
+	GAIN_SCALE_GAIN(64, BU27008_GSEL_64X),
+	GAIN_SCALE_GAIN(256, BU27008_GSEL_256X),
+	GAIN_SCALE_GAIN(512, BU27008_GSEL_512X),
+	GAIN_SCALE_GAIN(1024, BU27008_GSEL_1024X),
+};
+
+#define BU27008_MEAS_MODE_100MS		0x00
+#define BU27008_MEAS_MODE_55MS		0x01
+#define BU27008_MEAS_MODE_200MS		0x02
+#define BU27008_MEAS_MODE_400MS		0x04
+#define BU27008_MEAS_TIME_MAX_MS	400
+
+static const struct iio_itime_sel_mul bu27008_itimes[] = {
+	GAIN_SCALE_ITIME_US(400000, BU27008_MEAS_MODE_400MS, 8),
+	GAIN_SCALE_ITIME_US(200000, BU27008_MEAS_MODE_200MS, 4),
+	GAIN_SCALE_ITIME_US(100000, BU27008_MEAS_MODE_100MS, 2),
+	GAIN_SCALE_ITIME_US(55000, BU27008_MEAS_MODE_55MS, 1),
+};
+
+/*
+ * All the RGBC channels share the same gain.
+ * IR gain can be fine-tuned from the gain set for the RGBC by 2 bit, but this
+ * would yield quite complex gain setting. Especially since not all bit
+ * compinations are supported. And in any case setting GAIN for RGBC will
+ * always also change the IR-gain.
+ *
+ * On top of this, the selector '0' which corresponds to hw-gain 1X on RGBC,
+ * corresponds to gain 2X on IR. Rest of the selctors correspond to same gains
+ * though. This, however, makes it not possible to use shared gain for all
+ * RGBC and IR settings even though they are all changed at the one go.
+ */
+#define BU27008_CHAN(color, data, separate_avail)				\
+{										\
+	.type = IIO_INTENSITY,							\
+	.modified = 1,								\
+	.channel2 = IIO_MOD_LIGHT_##color,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |				\
+			      BIT(IIO_CHAN_INFO_SCALE),				\
+	.info_mask_separate_available = (separate_avail),			\
+	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),			\
+	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME),	\
+	.address = BU27008_REG_##data##_LO,					\
+	.scan_index = BU27008_##color,						\
+	.scan_type = {								\
+		.sign = 's',							\
+		.realbits = 16,							\
+		.storagebits = 16,						\
+		.endianness = IIO_LE,						\
+	},									\
+}
+
+/* For raw reads we always configure DATA3 for CLEAR */
+static const struct iio_chan_spec bu27008_channels[] = {
+	BU27008_CHAN(RED, DATA0, BIT(IIO_CHAN_INFO_SCALE)),
+	BU27008_CHAN(GREEN, DATA1, BIT(IIO_CHAN_INFO_SCALE)),
+	BU27008_CHAN(BLUE, DATA2, BIT(IIO_CHAN_INFO_SCALE)),
+	BU27008_CHAN(CLEAR, DATA2, BIT(IIO_CHAN_INFO_SCALE)),
+	/*
+	 * We don't allow setting scale for IR (because of shared gain bits).
+	 * Hence we don't advertise available ones either.
+	 */
+	BU27008_CHAN(IR, DATA3, 0),
+	IIO_CHAN_SOFT_TIMESTAMP(BU27008_NUM_CHANS),
+};
+
+struct bu27008_data {
+	struct regmap *regmap;
+	struct iio_trigger *trig;
+	struct device *dev;
+	struct iio_gts gts;
+	struct iio_gts gts_ir;
+	int irq;
+
+	/*
+	 * Prevent changing gain/time config when scale is read/written.
+	 * Similarly, protect the integration_time read/change sequence.
+	 * Prevent changing gain/time when data is read.
+	 */
+	struct mutex mutex;
+};
+
+static const struct regmap_range bu27008_volatile_ranges[] = {
+	{
+		.range_min = BU27008_REG_SYSTEM_CONTROL,	/* SWRESET */
+		.range_max = BU27008_REG_SYSTEM_CONTROL,
+	}, {
+		.range_min = BU27008_REG_MODE_CONTROL3,		/* VALID */
+		.range_max = BU27008_REG_MODE_CONTROL3,
+	}, {
+		.range_min = BU27008_REG_DATA0_LO,		/* DATA */
+		.range_max = BU27008_REG_DATA3_HI,
+	},
+};
+
+static const struct regmap_access_table bu27008_volatile_regs = {
+	.yes_ranges = &bu27008_volatile_ranges[0],
+	.n_yes_ranges = ARRAY_SIZE(bu27008_volatile_ranges),
+};
+
+static const struct regmap_range bu27008_read_only_ranges[] = {
+	{
+		.range_min = BU27008_REG_DATA0_LO,
+		.range_max = BU27008_REG_DATA3_HI,
+	}, {
+		.range_min = BU27008_REG_MANUFACTURER_ID,
+		.range_max = BU27008_REG_MANUFACTURER_ID,
+	},
+};
+
+static const struct regmap_access_table bu27008_ro_regs = {
+	.no_ranges = &bu27008_read_only_ranges[0],
+	.n_no_ranges = ARRAY_SIZE(bu27008_read_only_ranges),
+};
+
+static const struct regmap_config bu27008_regmap = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = BU27008_REG_MAX,
+	.cache_type = REGCACHE_RBTREE,
+	.volatile_table = &bu27008_volatile_regs,
+	.wr_table = &bu27008_ro_regs,
+	/*
+	 * All register writes are serialized by the mutex which protects the
+	 * scale setting/getting. This is needed because scale is combined by
+	 * gain and integration time settings and we need to ensure those are
+	 * not read / written when scale is being computed.
+	 *
+	 * As a result of this serializing, we don't need regmap locking. Note,
+	 * this is not true if we add any configurations which are not
+	 * serialized by the mutex and which may need for example a protected
+	 * read-modify-write cycle (eg. regmap_update_bits()). Please, revise
+	 * this when adding features to the driver.
+	 */
+	.disable_locking = true,
+};
+
+#define BU27008_MAX_VALID_RESULT_WAIT_US	50000
+#define BU27008_VALID_RESULT_WAIT_QUANTA_US	1000
+
+static int bu27008_chan_read_data(struct bu27008_data *data, int reg, int *val)
+{
+	int ret, valid;
+	__le16 tmp;
+
+	ret = regmap_read_poll_timeout(data->regmap, BU27008_REG_MODE_CONTROL3,
+				       valid, (valid & BU27008_MASK_VALID),
+				       BU27008_VALID_RESULT_WAIT_QUANTA_US,
+				       BU27008_MAX_VALID_RESULT_WAIT_US);
+	if (ret)
+		return ret;
+
+	ret = regmap_bulk_read(data->regmap, reg, &tmp, sizeof(tmp));
+	if (ret)
+		dev_err(data->dev, "Reading channel data failed\n");
+
+	*val = le16_to_cpu(tmp);
+
+	return ret;
+}
+
+static int bu27008_get_gain(struct bu27008_data *data, struct iio_gts *gts, int *gain)
+{
+	int ret, sel;
+
+	ret = regmap_read(data->regmap, BU27008_REG_MODE_CONTROL2, &sel);
+	if (ret)
+		return ret;
+
+	sel = FIELD_GET(BU27008_MASK_RGBC_GAIN, sel);
+
+	ret = iio_gts_find_gain_by_sel(gts, sel);
+	if (ret < 0) {
+		dev_err(data->dev, "unknown gain value 0x%x\n", sel);
+		return ret;
+	}
+
+	*gain = ret;
+
+	return 0;
+}
+
+static int bu27008_write_gain_sel(struct bu27008_data *data, int sel)
+{
+	int regval;
+
+	regval = FIELD_PREP(BU27008_MASK_RGBC_GAIN, sel);
+
+	/*
+	 * We do always set also the LOW bits of IR-gain because othervice we
+	 * would risk resulting an invalid GAIN register value.
+	 *
+	 * We could allow setting separate gains for RGBC and IR when the
+	 * values were such that HW could support both gain settings.
+	 * Eg, when the shared bits were same for both gain values.
+	 *
+	 * This, however, has a negligible benefit compared to the increased
+	 * software complexity when we would need to go through the gains
+	 * for both channels separately when the integration time changes.
+	 * This would end up with nasty logic for computing gain values for
+	 * both channels - and rejecting them if shared bits changed.
+	 *
+	 * We should then build the logic by guessing what a user prefers.
+	 * RGBC or IR gains correctly set while other jumps to odd value?
+	 * Maybe look-up a value where both gains are somehow optimized
+	 * <what this somehow is, is ATM unknown to us>. Or maybe user would
+	 * expect us to reject changes when optimal gains can't be set to both
+	 * channels w/given integration time. At best that would result
+	 * solution that works well for a very specific subset of
+	 * configurations but causes unexpected corner-cases.
+	 *
+	 * So, we keep it simple. Always set same selector to IR and RGBC.
+	 * We disallow setting IR (as I expect that most of the users are
+	 * interested in RGBC). This way we can show the user that the scales
+	 * for RGBC and IR channels are different (1X Vs 2X with sel 0) while
+	 * still keeping the operation deterministic.
+	 */
+	regval |= FIELD_PREP(BU27008_MASK_IR_GAIN_LO, sel);
+
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL2,
+				  BU27008_MASK_RGBC_GAIN, regval);
+}
+
+static int bu27008_set_gain(struct bu27008_data *data, int gain)
+{
+	int ret;
+
+	ret = iio_gts_find_sel_by_gain(&data->gts, gain);
+	if (ret < 0)
+		return ret;
+
+	return bu27008_write_gain_sel(data, ret);
+}
+
+static int bu27008_get_int_time_sel(struct bu27008_data *data, int *sel)
+{
+	int ret, val;
+
+	ret = regmap_read(data->regmap, BU27008_REG_MODE_CONTROL1, &val);
+	*sel = FIELD_GET(BU27008_MASK_MEAS_MODE, val);
+
+	return ret;
+}
+
+static int bu27008_set_int_time_sel(struct bu27008_data *data, int sel)
+{
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL1,
+				  BU27008_MASK_MEAS_MODE, sel);
+}
+
+static int bu27008_get_int_time_us(struct bu27008_data *data)
+{
+	int ret, sel;
+
+	ret = bu27008_get_int_time_sel(data, &sel);
+	if (ret)
+		return ret;
+
+	return iio_gts_find_int_time_by_sel(&data->gts, sel);
+}
+
+static int _bu27008_get_scale(struct bu27008_data *data, bool ir, int *val,
+			      int *val2)
+{
+	struct iio_gts *gts;
+	int gain, ret;
+
+	if (ir)
+		gts = &data->gts_ir;
+	else
+		gts = &data->gts;
+
+	ret = bu27008_get_gain(data, gts, &gain);
+	if (ret)
+		return ret;
+
+	ret = bu27008_get_int_time_us(data);
+	if (ret < 0)
+		return ret;
+
+	return iio_gts_get_scale(gts, gain, ret, val, val2);
+}
+
+static int bu27008_get_scale(struct bu27008_data *data, bool ir, int *val,
+			     int *val2)
+{
+	int ret;
+
+	mutex_lock(&data->mutex);
+	ret = _bu27008_get_scale(data, ir, val, val2);
+	mutex_unlock(&data->mutex);
+
+	return ret;
+}
+
+static int bu27008_set_int_time(struct bu27008_data *data, int time)
+{
+	int ret;
+
+	ret = iio_gts_find_sel_by_int_time(&data->gts, time);
+	if (ret < 0)
+		return ret;
+
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL1,
+				  BU27008_MASK_MEAS_MODE, ret);
+}
+
+/* Try to change the time so that the scale is maintained */
+static int bu27008_try_set_int_time(struct bu27008_data *data, int int_time_new)
+{
+	int ret, old_time_sel, new_time_sel,  old_gain, new_gain;
+
+	mutex_lock(&data->mutex);
+
+	ret = bu27008_get_int_time_sel(data, &old_time_sel);
+	if (ret < 0)
+		goto unlock_out;
+
+	if (!iio_gts_valid_time(&data->gts, int_time_new)) {
+		dev_dbg(data->dev, "Unsupported integration time %u\n",
+			int_time_new);
+
+		ret = -EINVAL;
+		goto unlock_out;
+	}
+
+	/* If we already use requested time, then we're done */
+	new_time_sel = iio_gts_find_sel_by_int_time(&data->gts, int_time_new);
+	if (new_time_sel == old_time_sel)
+		goto unlock_out;
+
+	ret = bu27008_get_gain(data, &data->gts, &old_gain);
+	if (ret)
+		goto unlock_out;
+
+	ret = iio_gts_find_new_gain_sel_by_old_gain_time(&data->gts, old_gain,
+				old_time_sel, new_time_sel, &new_gain);
+	if (ret) {
+		int scale1, scale2;
+		bool ok;
+
+		_bu27008_get_scale(data, false, &scale1, &scale2);
+		dev_dbg(data->dev,
+			"Can't support time %u with current scale %u %u\n",
+			int_time_new, scale1, scale2);
+
+		if (new_gain < 0)
+			goto unlock_out;
+
+		/*
+		 * If caller requests for integration time change and we
+		 * can't support the scale - then the caller should be
+		 * prepared to 'pick up the pieces and deal with the
+		 * fact that the scale changed'.
+		 */
+		ret = iio_find_closest_gain_low(&data->gts, new_gain, &ok);
+		if (!ok)
+			dev_dbg(data->dev, "optimal gain out of range\n");
+
+		if (ret < 0) {
+			dev_dbg(data->dev,
+				 "Total gain increase. Risk of saturation");
+			ret = iio_gts_get_min_gain(&data->gts);
+			if (ret < 0)
+				goto unlock_out;
+		}
+		new_gain = ret;
+		dev_dbg(data->dev, "scale changed, new gain %u\n", new_gain);
+	}
+
+	ret = bu27008_set_gain(data, new_gain);
+	if (ret)
+		goto unlock_out;
+
+	ret = bu27008_set_int_time(data, int_time_new);
+
+unlock_out:
+	mutex_unlock(&data->mutex);
+
+	return ret;
+}
+
+static int bu27008_meas_set(struct bu27008_data *data, int state)
+{
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL3,
+				  BU27008_MASK_MEAS_EN, state);
+}
+
+static int bu27008_chan_cfg(struct bu27008_data *data,
+			    struct iio_chan_spec const *chan)
+{
+	int chan_sel;
+
+	if (chan->scan_index == BU27008_BLUE)
+		chan_sel = BU27008_BLUE2_CLEAR3;
+	else
+		chan_sel = BU27008_CLEAR2_IR3;
+
+	chan_sel = FIELD_PREP(BU27008_MASK_CHAN_SEL, chan_sel);
+
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL3,
+				  BU27008_MASK_CHAN_SEL, chan_sel);
+}
+
+static int bu27008_read_one(struct bu27008_data *data, struct iio_dev *idev,
+			    struct iio_chan_spec const *chan, int *val, int *val2)
+{
+	int ret, int_time;
+
+	ret = bu27008_chan_cfg(data, chan);
+	if (ret)
+		return ret;
+
+	ret = bu27008_meas_set(data, BU27008_MEAS_EN);
+	if (ret)
+		return ret;
+
+	ret = bu27008_get_int_time_us(data);
+	if (ret < 0)
+		int_time = BU27008_MEAS_TIME_MAX_MS;
+	else
+		int_time = ret / USEC_PER_MSEC;
+
+	msleep(int_time);
+
+	ret = bu27008_chan_read_data(data, chan->address, val);
+	if (!ret)
+		ret = IIO_VAL_INT;
+
+	if (bu27008_meas_set(data, BU27008_MEAS_DIS))
+		dev_warn(data->dev, "measurement disabling failed\n");
+
+	return ret;
+}
+
+static int bu27008_read_raw(struct iio_dev *idev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct bu27008_data *data = iio_priv(idev);
+	int busy, ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		busy = iio_device_claim_direct_mode(idev);
+		if (busy)
+			return -EBUSY;
+
+		mutex_lock(&data->mutex);
+		ret = bu27008_read_one(data, idev, chan, val, val2);
+		mutex_unlock(&data->mutex);
+
+		iio_device_release_direct_mode(idev);
+
+		return ret;
+
+	case IIO_CHAN_INFO_SCALE:
+		ret = bu27008_get_scale(data, chan->scan_index == BU27008_IR,
+					val, val2);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT_PLUS_NANO;
+
+	case IIO_CHAN_INFO_INT_TIME:
+		ret = bu27008_get_int_time_us(data);
+		if (ret < 0)
+			return ret;
+
+		*val = 0;
+		*val2 = ret;
+
+		return IIO_VAL_INT_PLUS_MICRO;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+/* Called if the new scale could not be supported with existing int-time */
+static int bu27008_try_find_new_time_gain(struct bu27008_data *data, int val,
+					  int val2, int *gain_sel)
+{
+	int i, ret, new_time_sel;
+
+	for (i = 0; i < data->gts.num_itime; i++) {
+		new_time_sel = data->gts.itime_table[i].sel;
+		ret = iio_gts_find_gain_sel_for_scale_using_time(&data->gts,
+					new_time_sel, val, val2 * 1000, gain_sel);
+		if (!ret)
+			break;
+	}
+	if (i == data->gts.num_itime) {
+		dev_err(data->dev, "Can't support scale %u %u\n", val, val2);
+
+		return -EINVAL;
+	}
+
+	return bu27008_set_int_time_sel(data, new_time_sel);
+}
+
+static int bu27008_set_scale(struct bu27008_data *data,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2)
+{
+	int ret, gain_sel, time_sel;
+
+	if (chan->scan_index == BU27008_IR)
+		return -EINVAL;
+
+	mutex_lock(&data->mutex);
+
+	ret = bu27008_get_int_time_sel(data, &time_sel);
+	if (ret < 0)
+		goto unlock_out;
+
+	ret = iio_gts_find_gain_sel_for_scale_using_time(&data->gts, time_sel,
+						val, val2 * 1000, &gain_sel);
+	if (ret) {
+		ret = bu27008_try_find_new_time_gain(data, val, val2, &gain_sel);
+		if (ret)
+			goto unlock_out;
+
+	}
+	ret = bu27008_write_gain_sel(data, gain_sel);
+
+unlock_out:
+	mutex_unlock(&data->mutex);
+
+	return ret;
+}
+
+static int bu27008_write_raw(struct iio_dev *idev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long mask)
+{
+	struct bu27008_data *data = iio_priv(idev);
+	int ret;
+
+	/*
+	 * Do not allow changing scale when measurement is ongoing as doing so
+	 * could make values in the buffer inconsistent.
+	 */
+	ret = iio_device_claim_direct_mode(idev);
+	if (ret)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		ret = bu27008_set_scale(data, chan, val, val2);
+		break;
+	case IIO_CHAN_INFO_INT_TIME:
+		if (val) {
+			ret = -EINVAL;
+			break;
+		}
+		ret = bu27008_try_set_int_time(data, val2);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	iio_device_release_direct_mode(idev);
+
+	return ret;
+}
+
+static int bu27008_read_avail(struct iio_dev *idev,
+			      struct iio_chan_spec const *chan, const int **vals,
+			      int *type, int *length, long mask)
+{
+	struct bu27008_data *data = iio_priv(idev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_INT_TIME:
+		return iio_gts_avail_times(&data->gts, vals, type, length);
+	case IIO_CHAN_INFO_SCALE:
+		if (chan->channel2 == IIO_MOD_LIGHT_IR)
+			return iio_gts_all_avail_scales(&data->gts_ir, vals,
+							type, length);
+		return iio_gts_all_avail_scales(&data->gts, vals, type, length);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int bu27008_update_scan_mode(struct iio_dev *idev,
+				    const unsigned long *scan_mask)
+{
+	struct bu27008_data *data = iio_priv(idev);
+	int chan_sel;
+
+	/* Configure channel selection */
+	if (test_bit(BU27008_BLUE, idev->active_scan_mask)) {
+		if (test_bit(BU27008_CLEAR, idev->active_scan_mask))
+			chan_sel = BU27008_BLUE2_CLEAR3;
+		else
+			chan_sel = BU27008_BLUE2_IR3;
+	} else {
+		chan_sel = BU27008_CLEAR2_IR3;
+	}
+
+	chan_sel = FIELD_PREP(BU27008_MASK_CHAN_SEL, chan_sel);
+
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL3,
+				 BU27008_MASK_CHAN_SEL, chan_sel);
+}
+
+static const struct iio_info bu27008_info = {
+	.read_raw = &bu27008_read_raw,
+	.write_raw = &bu27008_write_raw,
+	.read_avail = &bu27008_read_avail,
+	.update_scan_mode = bu27008_update_scan_mode,
+	.validate_trigger = iio_validate_own_trigger,
+};
+
+static int bu27008_chip_init(struct bu27008_data *data)
+{
+	int ret;
+
+	ret = regmap_write_bits(data->regmap, BU27008_REG_SYSTEM_CONTROL,
+				BU27008_MASK_SW_RESET, BU27008_MASK_SW_RESET);
+	if (ret)
+		return dev_err_probe(data->dev, ret, "Sensor reset failed\n");
+
+	/*
+	 * The data-sheet does not tell how long performing the IC reset takes.
+	 * However, the data-sheet says the minimum time it takes the IC to be
+	 * able to take inputs after power is applied, is 100 uS. I'd assume
+	 * > 1 mS is enough.
+	 */
+	msleep(1);
+
+	ret = regmap_reinit_cache(data->regmap, &bu27008_regmap);
+	if (ret)
+		dev_err(data->dev, "Failed to reinit reg cache\n");
+
+	return ret;
+}
+
+static int bu27008_set_drdy_irq(struct bu27008_data *data, int state)
+{
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL3,
+				 BU27008_MASK_INT_EN, state);
+}
+
+static int bu27008_trigger_set_state(struct iio_trigger *trig,
+				     bool state)
+{
+	struct bu27008_data *data = iio_trigger_get_drvdata(trig);
+	int ret;
+
+	if (state)
+		ret = bu27008_set_drdy_irq(data, BU27008_INT_EN);
+	else
+		ret = bu27008_set_drdy_irq(data, BU27008_INT_DIS);
+	if (ret)
+		dev_err(data->dev, "Failed to set trigger state\n");
+
+	return ret;
+}
+
+static void bu27008_trigger_reenable(struct iio_trigger *trig)
+{
+	struct bu27008_data *data = iio_trigger_get_drvdata(trig);
+
+	enable_irq(data->irq);
+}
+
+static const struct iio_trigger_ops bu27008_trigger_ops = {
+	.set_trigger_state = bu27008_trigger_set_state,
+	.reenable = bu27008_trigger_reenable,
+};
+
+static irqreturn_t bu27008_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *idev = pf->indio_dev;
+	struct bu27008_data *data = iio_priv(idev);
+	struct {
+		__le16 chan[BU27008_NUM_HW_CHANS];
+		s64 ts __aligned(8);
+	} raw;
+	int ret, dummy;
+
+	memset(&raw, 0, sizeof(raw));
+
+	/*
+	 * After some measurements, it seems reading the
+	 * BU27008_REG_MODE_CONTROL3 debounces the IRQ line
+	 */
+	ret = regmap_read(data->regmap, BU27008_REG_MODE_CONTROL3, &dummy);
+	if (ret < 0)
+		goto err_read;
+
+	ret = regmap_bulk_read(data->regmap, BU27008_REG_DATA0_LO, &raw.chan,
+			       sizeof(raw.chan));
+	if (ret < 0)
+		goto err_read;
+
+	iio_push_to_buffers_with_timestamp(idev, &raw, pf->timestamp);
+err_read:
+	iio_trigger_notify_done(idev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int bu27008_buffer_preenable(struct iio_dev *idev)
+{
+	struct bu27008_data *data = iio_priv(idev);
+
+	return bu27008_meas_set(data, BU27008_MEAS_EN);
+}
+
+static int bu27008_buffer_postdisable(struct iio_dev *idev)
+{
+	struct bu27008_data *data = iio_priv(idev);
+
+	return bu27008_meas_set(data, BU27008_MEAS_DIS);
+}
+
+static const struct iio_buffer_setup_ops bu27008_buffer_ops = {
+	.preenable = bu27008_buffer_preenable,
+	.postdisable = bu27008_buffer_postdisable,
+};
+
+static irqreturn_t bu27008_data_rdy_poll(int irq, void *private)
+{
+	/*
+	 * The BU27008 keeps IRQ asserted until we read the VALID bit from
+	 * a register. We need to keep the IRQ disabled until then.
+	 */
+	disable_irq_nosync(irq);
+	iio_trigger_poll(private);
+
+	return IRQ_HANDLED;
+}
+
+static int bu27008_setup_trigger(struct bu27008_data *data, struct iio_dev *idev)
+{
+	struct iio_trigger *itrig;
+	char *name;
+	int ret;
+
+	ret = devm_iio_triggered_buffer_setup(data->dev, idev,
+					      &iio_pollfunc_store_time,
+					      bu27008_trigger_handler,
+					      &bu27008_buffer_ops);
+	if (ret)
+		return dev_err_probe(data->dev, ret,
+			     "iio_triggered_buffer_setup_ext FAIL\n");
+
+	itrig = devm_iio_trigger_alloc(data->dev, "%sdata-rdy-dev%d",
+				       idev->name, iio_device_id(idev));
+	if (!itrig)
+		return -ENOMEM;
+
+	data->trig = itrig;
+
+	itrig->ops = &bu27008_trigger_ops;
+	iio_trigger_set_drvdata(itrig, data);
+
+	name = devm_kasprintf(data->dev, GFP_KERNEL, "%s-bu27008",
+			      dev_name(data->dev));
+
+	ret = devm_request_irq(data->dev, data->irq,
+			       &bu27008_data_rdy_poll,
+			       0, name, itrig);
+	if (ret)
+		return dev_err_probe(data->dev, ret, "Could not request IRQ\n");
+
+	ret = devm_iio_trigger_register(data->dev, itrig);
+	if (ret)
+		return dev_err_probe(data->dev, ret,
+				     "Trigger registration failed\n");
+
+	/* set default trigger */
+	idev->trig = iio_trigger_get(itrig);
+
+	return 0;
+}
+
+static int bu27008_probe(struct i2c_client *i2c)
+{
+	struct device *dev = &i2c->dev;
+	struct bu27008_data *data;
+	struct regmap *regmap;
+	unsigned int part_id, reg;
+	struct iio_dev *idev;
+	int ret;
+
+	regmap = devm_regmap_init_i2c(i2c, &bu27008_regmap);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap),
+				     "Failed to initialize Regmap\n");
+
+	idev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!idev)
+		return -ENOMEM;
+
+	ret = devm_regulator_get_enable(dev, "vdd");
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to get regulator\n");
+
+	data = iio_priv(idev);
+
+	ret = regmap_read(regmap, BU27008_REG_SYSTEM_CONTROL, &reg);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to access sensor\n");
+
+	part_id = FIELD_GET(BU27008_MASK_PART_ID, reg);
+
+	if (part_id != BU27008_ID)
+		dev_warn(dev, "unknown device 0x%x\n", part_id);
+
+	ret = devm_iio_init_iio_gts(dev, BU27008_SCALE_1X, 0, bu27008_gains,
+				    ARRAY_SIZE(bu27008_gains), bu27008_itimes,
+				    ARRAY_SIZE(bu27008_itimes), &data->gts);
+	if (ret)
+		return ret;
+
+	ret = devm_iio_init_iio_gts(dev, BU27008_SCALE_1X, 0, bu27008_gains_ir,
+				    ARRAY_SIZE(bu27008_gains_ir), bu27008_itimes,
+				    ARRAY_SIZE(bu27008_itimes), &data->gts_ir);
+	if (ret)
+		return ret;
+
+	mutex_init(&data->mutex);
+	data->regmap = regmap;
+	data->dev = dev;
+	data->irq = i2c->irq;
+
+	idev->channels = bu27008_channels;
+	idev->num_channels = ARRAY_SIZE(bu27008_channels);
+	idev->name = "bu27008";
+	idev->info = &bu27008_info;
+	idev->modes = INDIO_DIRECT_MODE;
+	idev->available_scan_masks = bu27008_scan_masks;
+
+	ret = bu27008_chip_init(data);
+	if (ret)
+		return ret;
+
+	if (i2c->irq) {
+		ret = bu27008_setup_trigger(data, idev);
+		if (ret)
+			return ret;
+	} else {
+		dev_info(dev, "No IRQ, buffered mode disabled\n");
+	}
+
+	ret = devm_iio_device_register(dev, idev);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Unable to register iio device\n");
+
+	return 0;
+}
+
+static const struct of_device_id bu27008_of_match[] = {
+	{ .compatible = "rohm,bu27008" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, bu27008_of_match);
+
+static struct i2c_driver bu27008_i2c_driver = {
+	.driver = {
+		.name = "bu27008",
+		.of_match_table = bu27008_of_match,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+	.probe = bu27008_probe,
+};
+module_i2c_driver(bu27008_i2c_driver);
+
+MODULE_DESCRIPTION("ROHM BU27008 colour sensor driver");
+MODULE_AUTHOR("Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS(IIO_GTS_HELPER);