staging: iio: light: isl29018: Use standard sysfs attributes for scale and integration time

This patch refactors the isl29018 driver code in order to use standard
sysfs attributes for scale and integration time.

ISL29018 light sensor uses four ranges and four ADC's resolutions
which influence the calculated lux. Adc resolution is strongly
connected to integration time and range should be controlled by scale.

This patch introduces the usage of integration time and scale instead
of adc resolution and range.

Signed-off-by: Roberta Dobrescu <roberta.dobrescu@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/light/isl29018.c

@@ -66,6 +66,39 @@
 #define ISL29035_BOUT_SHIFT		0x07
 #define ISL29035_BOUT_MASK		(0x01 << ISL29035_BOUT_SHIFT)
 
+#define ISL29018_INT_TIME_AVAIL		"0.090000 0.005630 0.000351 0.000021"
+#define ISL29023_INT_TIME_AVAIL		"0.090000 0.005600 0.000352 0.000022"
+#define ISL29035_INT_TIME_AVAIL		"0.105000 0.006500 0.000410 0.000025"
+
+static const char * const int_time_avail[] = {
+	ISL29018_INT_TIME_AVAIL,
+	ISL29023_INT_TIME_AVAIL,
+	ISL29035_INT_TIME_AVAIL,
+};
+
+enum isl29018_int_time {
+	ISL29018_INT_TIME_16,
+	ISL29018_INT_TIME_12,
+	ISL29018_INT_TIME_8,
+	ISL29018_INT_TIME_4,
+};
+
+static const unsigned int isl29018_int_utimes[3][4] = {
+	{90000, 5630, 351, 21},
+	{90000, 5600, 352, 22},
+	{105000, 6500, 410, 25},
+};
+
+static const struct isl29018_scale {
+	unsigned int scale;
+	unsigned int uscale;
+} isl29018_scales[4][4] = {
+	{ {0, 15258}, {0, 61035}, {0, 244140}, {0, 976562} },
+	{ {0, 244140}, {0, 976562}, {3, 906250}, {15, 625000} },
+	{ {3, 906250}, {15, 625000}, {62, 500000}, {250, 0} },
+	{ {62, 500000}, {250, 0}, {1000, 0}, {4000, 0} }
+};
+
 struct isl29018_chip {
 	struct device		*dev;
 	struct regmap		*regmap;
@@ -73,51 +106,75 @@ struct isl29018_chip {
 	int			type;
 	unsigned int		calibscale;
 	unsigned int		ucalibscale;
-	unsigned int		range;
-	unsigned int		adc_bit;
+	unsigned int		int_time;
+	struct isl29018_scale	scale;
 	int			prox_scheme;
 	bool			suspended;
 };
 
-static int isl29018_set_range(struct isl29018_chip *chip, unsigned long range,
-		unsigned int *new_range)
+static int isl29018_set_integration_time(struct isl29018_chip *chip,
+					 unsigned int utime)
 {
-	static const unsigned long supp_ranges[] = {1000, 4000, 16000, 64000};
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(supp_ranges); ++i) {
-		if (range <= supp_ranges[i]) {
-			*new_range = (unsigned int)supp_ranges[i];
+	int i, ret;
+	unsigned int int_time, new_int_time;
+	struct isl29018_scale new_scale;
+
+	for (i = 0; i < ARRAY_SIZE(isl29018_int_utimes[chip->type]); ++i) {
+		if (utime == isl29018_int_utimes[chip->type][i]) {
+			new_int_time = i;
+			new_scale = isl29018_scales[new_int_time][0];
 			break;
 		}
 	}
 
-	if (i >= ARRAY_SIZE(supp_ranges))
+	if (i >= ARRAY_SIZE(isl29018_int_utimes[chip->type]))
 		return -EINVAL;
 
-	return regmap_update_bits(chip->regmap, ISL29018_REG_ADD_COMMANDII,
-			COMMANDII_RANGE_MASK, i << COMMANDII_RANGE_SHIFT);
+	ret = regmap_update_bits(chip->regmap, ISL29018_REG_ADD_COMMANDII,
+				 COMMANDII_RESOLUTION_MASK,
+				 i << COMMANDII_RESOLUTION_SHIFT);
+	if (ret < 0)
+		return ret;
+
+	/* keep the same range when integration time changes */
+	int_time = chip->int_time;
+	for (i = 0; i < ARRAY_SIZE(isl29018_scales[int_time]); ++i) {
+		if (chip->scale.scale == isl29018_scales[int_time][i].scale &&
+		    chip->scale.uscale == isl29018_scales[int_time][i].uscale) {
+			chip->scale = isl29018_scales[new_int_time][i];
+			break;
+		}
+	}
+	chip->int_time = new_int_time;
+
+	return 0;
 }
 
-static int isl29018_set_resolution(struct isl29018_chip *chip,
-			unsigned long adcbit, unsigned int *conf_adc_bit)
+static int isl29018_set_scale(struct isl29018_chip *chip, int scale, int uscale)
 {
-	static const unsigned long supp_adcbit[] = {16, 12, 8, 4};
-	int i;
+	int i, ret;
+	struct isl29018_scale new_scale;
 
-	for (i = 0; i < ARRAY_SIZE(supp_adcbit); ++i) {
-		if (adcbit >= supp_adcbit[i]) {
-			*conf_adc_bit = (unsigned int)supp_adcbit[i];
+	for (i = 0; i < ARRAY_SIZE(isl29018_scales[chip->int_time]); ++i) {
+		if (scale == isl29018_scales[chip->int_time][i].scale &&
+		    uscale == isl29018_scales[chip->int_time][i].uscale) {
+			new_scale = isl29018_scales[chip->int_time][i];
 			break;
 		}
 	}
 
-	if (i >= ARRAY_SIZE(supp_adcbit))
+	if (i >= ARRAY_SIZE(isl29018_scales[chip->int_time]))
 		return -EINVAL;
 
-	return regmap_update_bits(chip->regmap, ISL29018_REG_ADD_COMMANDII,
-			COMMANDII_RESOLUTION_MASK,
-			i << COMMANDII_RESOLUTION_SHIFT);
+	ret = regmap_update_bits(chip->regmap, ISL29018_REG_ADD_COMMANDII,
+				 COMMANDII_RANGE_MASK,
+				 i << COMMANDII_RANGE_SHIFT);
+	if (ret < 0)
+		return ret;
+
+	chip->scale = new_scale;
+
+	return 0;
 }
 
 static int isl29018_read_sensor_input(struct isl29018_chip *chip, int mode)
@@ -156,22 +213,17 @@ static int isl29018_read_sensor_input(struct isl29018_chip *chip, int mode)
 static int isl29018_read_lux(struct isl29018_chip *chip, int *lux)
 {
 	int lux_data;
-	unsigned int data_x_range, lux_unshifted;
+	unsigned int data_x_range;
 
 	lux_data = isl29018_read_sensor_input(chip, COMMMAND1_OPMODE_ALS_ONCE);
 
 	if (lux_data < 0)
 		return lux_data;
 
-	/* To support fractional scaling, separate the unshifted lux
-	 * into two calculations: int scaling and micro-scaling.
-	 * ucalibscale ranges from 0-999999, so about 20 bits.  Split
-	 * the /1,000,000 in two to reduce the risk of over/underflow.
-	 */
-	data_x_range = lux_data * chip->range;
-	lux_unshifted = data_x_range * chip->calibscale;
-	lux_unshifted += data_x_range / 1000 * chip->ucalibscale / 1000;
-	*lux = lux_unshifted >> chip->adc_bit;
+	data_x_range = lux_data * chip->scale.scale +
+		       lux_data * chip->scale.uscale / 1000000;
+	*lux = data_x_range * chip->calibscale +
+	       data_x_range * chip->ucalibscale / 1000000;
 
 	return 0;
 }
@@ -229,7 +281,39 @@ static int isl29018_read_proximity_ir(struct isl29018_chip *chip, int scheme,
 	return 0;
 }
 
-/* Sysfs interface */
+static ssize_t show_scale_available(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct isl29018_chip *chip = iio_priv(indio_dev);
+	int i, len = 0;
+
+	for (i = 0; i < ARRAY_SIZE(isl29018_scales[chip->int_time]); ++i)
+		len += sprintf(buf + len, "%d.%06d ",
+			       isl29018_scales[chip->int_time][i].scale,
+			       isl29018_scales[chip->int_time][i].uscale);
+
+	buf[len - 1] = '\n';
+
+	return len;
+}
+
+static ssize_t show_int_time_available(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct isl29018_chip *chip = iio_priv(indio_dev);
+	int i, len = 0;
+
+	for (i = 0; i < ARRAY_SIZE(isl29018_int_utimes[chip->type]); ++i)
+		len += sprintf(buf + len, "0.%06d ",
+			       isl29018_int_utimes[chip->type][i]);
+
+	buf[len - 1] = '\n';
+
+	return len;
+}
+
 /* proximity scheme */
 static ssize_t show_prox_infrared_suppression(struct device *dev,
 			struct device_attribute *attr, char *buf)
@@ -276,11 +360,28 @@ static int isl29018_write_raw(struct iio_dev *indio_dev,
 	int ret = -EINVAL;
 
 	mutex_lock(&chip->lock);
-	if (mask == IIO_CHAN_INFO_CALIBSCALE && chan->type == IIO_LIGHT) {
-		chip->calibscale = val;
-		/* With no write_raw_get_fmt(), val2 is a MICRO fraction. */
-		chip->ucalibscale = val2;
-		ret = 0;
+	switch (mask) {
+	case IIO_CHAN_INFO_CALIBSCALE:
+		if (chan->type == IIO_LIGHT) {
+			chip->calibscale = val;
+			chip->ucalibscale = val2;
+			ret = 0;
+		}
+		break;
+	case IIO_CHAN_INFO_INT_TIME:
+		if (chan->type == IIO_LIGHT)
+			if (val != 0) {
+				mutex_unlock(&chip->lock);
+				return -EINVAL;
+			}
+			ret = isl29018_set_integration_time(chip, val2);
+		break;
+	case IIO_CHAN_INFO_SCALE:
+		if (chan->type == IIO_LIGHT)
+			ret = isl29018_set_scale(chip, val, val2);
+		break;
+	default:
+		break;
 	}
 	mutex_unlock(&chip->lock);
 
@@ -321,6 +422,20 @@ static int isl29018_read_raw(struct iio_dev *indio_dev,
 		if (!ret)
 			ret = IIO_VAL_INT;
 		break;
+	case IIO_CHAN_INFO_INT_TIME:
+		if (chan->type == IIO_LIGHT) {
+			*val = 0;
+			*val2 = isl29018_int_utimes[chip->type][chip->int_time];
+			ret = IIO_VAL_INT_PLUS_MICRO;
+		}
+		break;
+	case IIO_CHAN_INFO_SCALE:
+		if (chan->type == IIO_LIGHT) {
+			*val = chip->scale.scale;
+			*val2 = chip->scale.uscale;
+			ret = IIO_VAL_INT_PLUS_MICRO;
+		}
+		break;
 	case IIO_CHAN_INFO_CALIBSCALE:
 		if (chan->type == IIO_LIGHT) {
 			*val = chip->calibscale;
@@ -340,7 +455,9 @@ static int isl29018_read_raw(struct iio_dev *indio_dev,
 	.indexed = 1,							\
 	.channel = 0,							\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |		\
-	BIT(IIO_CHAN_INFO_CALIBSCALE),					\
+	BIT(IIO_CHAN_INFO_CALIBSCALE) |					\
+	BIT(IIO_CHAN_INFO_SCALE) |					\
+	BIT(IIO_CHAN_INFO_INT_TIME),					\
 }
 
 #define ISL29018_IR_CHANNEL {						\
@@ -366,19 +483,27 @@ static const struct iio_chan_spec isl29023_channels[] = {
 	ISL29018_IR_CHANNEL,
 };
 
+static IIO_DEVICE_ATTR(in_illuminance_integration_time_available, S_IRUGO,
+		       show_int_time_available, NULL, 0);
+static IIO_DEVICE_ATTR(in_illuminance_scale_available, S_IRUGO,
+		      show_scale_available, NULL, 0);
 static IIO_DEVICE_ATTR(proximity_on_chip_ambient_infrared_suppression,
 					S_IRUGO | S_IWUSR,
 					show_prox_infrared_suppression,
 					store_prox_infrared_suppression, 0);
 
 #define ISL29018_DEV_ATTR(name) (&iio_dev_attr_##name.dev_attr.attr)
-#define ISL29018_CONST_ATTR(name) (&iio_const_attr_##name.dev_attr.attr)
+
 static struct attribute *isl29018_attributes[] = {
+	ISL29018_DEV_ATTR(in_illuminance_scale_available),
+	ISL29018_DEV_ATTR(in_illuminance_integration_time_available),
 	ISL29018_DEV_ATTR(proximity_on_chip_ambient_infrared_suppression),
 	NULL
 };
 
 static struct attribute *isl29023_attributes[] = {
+	ISL29018_DEV_ATTR(in_illuminance_scale_available),
+	ISL29018_DEV_ATTR(in_illuminance_integration_time_available),
 	NULL
 };
 
@@ -422,8 +547,6 @@ enum {
 static int isl29018_chip_init(struct isl29018_chip *chip)
 {
 	int status;
-	unsigned int new_adc_bit;
-	unsigned int new_range;
 
 	if (chip->type == isl29035) {
 		status = isl29035_detect(chip);
@@ -472,14 +595,19 @@ static int isl29018_chip_init(struct isl29018_chip *chip)
 	usleep_range(1000, 2000);	/* per data sheet, page 10 */
 
 	/* set defaults */
-	status = isl29018_set_range(chip, chip->range, &new_range);
+	status = isl29018_set_scale(chip, chip->scale.scale,
+				    chip->scale.uscale);
 	if (status < 0) {
 		dev_err(chip->dev, "Init of isl29018 fails\n");
 		return status;
 	}
 
-	status = isl29018_set_resolution(chip, chip->adc_bit,
-						&new_adc_bit);
+	status = isl29018_set_integration_time(chip,
+			isl29018_int_utimes[chip->type][chip->int_time]);
+	if (status < 0) {
+		dev_err(chip->dev, "Init of isl29018 fails\n");
+		return status;
+	}
 
 	return 0;
 }
@@ -609,8 +737,8 @@ static int isl29018_probe(struct i2c_client *client,
 	chip->type = dev_id;
 	chip->calibscale = 1;
 	chip->ucalibscale = 0;
-	chip->range = 1000;
-	chip->adc_bit = 16;
+	chip->int_time = ISL29018_INT_TIME_16;
+	chip->scale = isl29018_scales[chip->int_time][0];
 	chip->suspended = false;
 
 	chip->regmap = devm_regmap_init_i2c(client,