iio: ltr501: Add integration time support

Added support to modify and read ALS integration time.
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/ltr501.c

@@ -28,6 +28,7 @@
 
 #define LTR501_ALS_CONTR 0x80 /* ALS operation mode, SW reset */
 #define LTR501_PS_CONTR 0x81 /* PS operation mode */
+#define LTR501_ALS_MEAS_RATE 0x85 /* ALS integ time, measurement rate*/
 #define LTR501_PART_ID 0x86
 #define LTR501_MANUFAC_ID 0x87
 #define LTR501_ALS_DATA1 0x88 /* 16-bit, little endian */
@@ -49,11 +50,17 @@
 
 #define LTR501_REGMAP_NAME "ltr501_regmap"
 
+static const int int_time_mapping[] = {100000, 50000, 200000, 400000};
+
+static const struct reg_field reg_field_it =
+				REG_FIELD(LTR501_ALS_MEAS_RATE, 3, 4);
+
 struct ltr501_data {
 	struct i2c_client *client;
 	struct mutex lock_als, lock_ps;
 	u8 als_contr, ps_contr;
 	struct regmap *regmap;
+	struct regmap_field *reg_it;
 };
 
 static int ltr501_drdy(struct ltr501_data *data, u8 drdy_mask)
@@ -74,6 +81,58 @@ static int ltr501_drdy(struct ltr501_data *data, u8 drdy_mask)
 	return -EIO;
 }
 
+static int ltr501_set_it_time(struct ltr501_data *data, int it)
+{
+	int ret, i, index = -1, status;
+
+	for (i = 0; i < ARRAY_SIZE(int_time_mapping); i++) {
+		if (int_time_mapping[i] == it) {
+			index = i;
+			break;
+		}
+	}
+	/* Make sure integ time index is valid */
+	if (index < 0)
+		return -EINVAL;
+
+	ret = regmap_read(data->regmap, LTR501_ALS_CONTR, &status);
+	if (ret < 0)
+		return ret;
+
+	if (status & LTR501_CONTR_ALS_GAIN_MASK) {
+		/*
+		 * 200 ms and 400 ms integ time can only be
+		 * used in dynamic range 1
+		 */
+		if (index > 1)
+			return -EINVAL;
+	} else
+		/* 50 ms integ time can only be used in dynamic range 2 */
+		if (index == 1)
+			return -EINVAL;
+
+	return regmap_field_write(data->reg_it, index);
+}
+
+/* read int time in micro seconds */
+static int ltr501_read_it_time(struct ltr501_data *data, int *val, int *val2)
+{
+	int ret, index;
+
+	ret = regmap_field_read(data->reg_it, &index);
+	if (ret < 0)
+		return ret;
+
+	/* Make sure integ time index is valid */
+	if (index < 0 || index >= ARRAY_SIZE(int_time_mapping))
+		return -EINVAL;
+
+	*val2 = int_time_mapping[index];
+	*val = 0;
+
+	return IIO_VAL_INT_PLUS_MICRO;
+}
+
 static int ltr501_read_als(struct ltr501_data *data, __le16 buf[2])
 {
 	int ret;
@@ -121,7 +180,8 @@ static int ltr501_read_ps(struct ltr501_data *data)
 static const struct iio_chan_spec ltr501_channels[] = {
 	LTR501_INTENSITY_CHANNEL(0, LTR501_ALS_DATA0, IIO_MOD_LIGHT_BOTH, 0),
 	LTR501_INTENSITY_CHANNEL(1, LTR501_ALS_DATA1, IIO_MOD_LIGHT_IR,
-				 BIT(IIO_CHAN_INFO_SCALE)),
+				 BIT(IIO_CHAN_INFO_SCALE) |
+				 BIT(IIO_CHAN_INFO_INT_TIME)),
 	{
 		.type = IIO_PROXIMITY,
 		.address = LTR501_PS_DATA,
@@ -196,6 +256,13 @@ static int ltr501_read_raw(struct iio_dev *indio_dev,
 		default:
 			return -EINVAL;
 		}
+	case IIO_CHAN_INFO_INT_TIME:
+		switch (chan->type) {
+		case IIO_INTENSITY:
+			return ltr501_read_it_time(data, val, val2);
+		default:
+			return -EINVAL;
+		}
 	}
 	return -EINVAL;
 }
@@ -246,16 +313,30 @@ static int ltr501_write_raw(struct iio_dev *indio_dev,
 		default:
 			return -EINVAL;
 		}
+	case IIO_CHAN_INFO_INT_TIME:
+		switch (chan->type) {
+		case IIO_INTENSITY:
+			if (val != 0)
+				return -EINVAL;
+			mutex_lock(&data->lock_als);
+			i = ltr501_set_it_time(data, val2);
+			mutex_unlock(&data->lock_als);
+			return i;
+		default:
+			return -EINVAL;
+		}
 	}
 	return -EINVAL;
 }
 
 static IIO_CONST_ATTR(in_proximity_scale_available, "1 0.25 0.125 0.0625");
 static IIO_CONST_ATTR(in_intensity_scale_available, "1 0.005");
+static IIO_CONST_ATTR_INT_TIME_AVAIL("0.05 0.1 0.2 0.4");
 
 static struct attribute *ltr501_attributes[] = {
 	&iio_const_attr_in_proximity_scale_available.dev_attr.attr,
 	&iio_const_attr_in_intensity_scale_available.dev_attr.attr,
+	&iio_const_attr_integration_time_available.dev_attr.attr,
 	NULL
 };
 
@@ -404,6 +485,13 @@ static int ltr501_probe(struct i2c_client *client,
 	mutex_init(&data->lock_als);
 	mutex_init(&data->lock_ps);
 
+	data->reg_it = devm_regmap_field_alloc(&client->dev, regmap,
+					       reg_field_it);
+	if (IS_ERR(data->reg_it)) {
+		dev_err(&client->dev, "Integ time reg field init failed.\n");
+		return PTR_ERR(data->reg_it);
+	}
+
 	ret = regmap_read(data->regmap, LTR501_PART_ID, &partid);
 	if (ret < 0)
 		return ret;