max44000: Initial support for proximity reading

The proximity sensor relies on sending pulses to an external IR led and
it is disabled by default on powerup. The driver will enable it with a
default power setting.
Signed-off-by: Crestez Dan Leonard <leonard.crestez@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/max44000.c

@@ -59,6 +59,11 @@
  */
 #define MAX44000_REG_CFG_RX_DEFAULT 0xf0
 
+/* REG_TX bits */
+#define MAX44000_LED_CURRENT_MASK	0xf
+#define MAX44000_LED_CURRENT_MAX	11
+#define MAX44000_LED_CURRENT_DEFAULT	6
+
 #define MAX44000_ALSDATA_OVERFLOW	0x4000
 
 struct max44000_data {
@@ -75,6 +80,11 @@ static const struct iio_chan_spec max44000_channels[] = {
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
 	},
+	{
+		.type = IIO_PROXIMITY,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+	},
 };
 
 static int max44000_read_alsval(struct max44000_data *data)
@@ -104,11 +114,23 @@ static int max44000_read_alsval(struct max44000_data *data)
 	return regval;
 }
 
+static int max44000_write_led_current_raw(struct max44000_data *data, int val)
+{
+	/* Maybe we should clamp the value instead? */
+	if (val < 0 || val > MAX44000_LED_CURRENT_MAX)
+		return -ERANGE;
+	if (val >= 8)
+		val += 4;
+	return regmap_write_bits(data->regmap, MAX44000_REG_CFG_TX,
+				 MAX44000_LED_CURRENT_MASK, val);
+}
+
 static int max44000_read_raw(struct iio_dev *indio_dev,
 			     struct iio_chan_spec const *chan,
 			     int *val, int *val2, long mask)
 {
 	struct max44000_data *data = iio_priv(indio_dev);
+	unsigned int regval;
 	int ret;
 
 	switch (mask) {
@@ -123,6 +145,15 @@ static int max44000_read_raw(struct iio_dev *indio_dev,
 			*val = ret;
 			return IIO_VAL_INT;
 
+		case IIO_PROXIMITY:
+			mutex_lock(&data->lock);
+			ret = regmap_read(data->regmap, MAX44000_REG_PRX_DATA, &regval);
+			mutex_unlock(&data->lock);
+			if (ret < 0)
+				return ret;
+			*val = regval;
+			return IIO_VAL_INT;
+
 		default:
 			return -EINVAL;
 		}
@@ -260,14 +291,26 @@ static int max44000_probe(struct i2c_client *client,
 	 */
 
 	/* Reset ALS scaling bits */
-	ret = regmap_write(data->regmap, MAX44000_REG_CFG_RX, MAX44000_REG_CFG_RX_DEFAULT);
+	ret = regmap_write(data->regmap, MAX44000_REG_CFG_RX,
+			   MAX44000_REG_CFG_RX_DEFAULT);
+	if (ret < 0) {
+		dev_err(&client->dev, "failed to write default CFG_RX: %d\n",
+			ret);
+		return ret;
+	}
+
+	/*
+	 * By default the LED pulse used for the proximity sensor is disabled.
+	 * Set a middle value so that we get some sort of valid data by default.
+	 */
+	ret = max44000_write_led_current_raw(data, MAX44000_LED_CURRENT_DEFAULT);
 	if (ret < 0) {
-		dev_err(&client->dev, "failed to write default CFG_RX: %d\n", ret);
+		dev_err(&client->dev, "failed to write init config: %d\n", ret);
 		return ret;
 	}
 
-	/* Reset CFG bits to ALS-only mode and no interrupts */
-	reg = MAX44000_CFG_TRIM | MAX44000_CFG_MODE_ALS_GIR;
+	/* Reset CFG bits to ALS_PRX mode which allows easy reading of both values. */
+	reg = MAX44000_CFG_TRIM | MAX44000_CFG_MODE_ALS_PRX;
 	ret = regmap_write(data->regmap, MAX44000_REG_CFG_MAIN, reg);
 	if (ret < 0) {
 		dev_err(&client->dev, "failed to write init config: %d\n", ret);