iio: light: vcnl4000: Add oversampling_ratio for 4040/4200

Add the proximity multi pulse (PS_MPS) as oversampling_ratio.
Instead of one single pulse per every defined time frame, one can
program2, 4, or even 8 pulses. This leads to a longer IRED on-time
for each proximity measurement value, which also results in a higher
detection range.

Add read/write attribute for proximity oversampling-ratio and read
attribute for available oversampling-ratio.
This is supported for vcnl4040 and vcnl4200.
Signed-off-by: Astrid Rost <astrid.rost@axis.com>
Link: https://lore.kernel.org/r/20230613135025.2596641-8-astrid.rost@axis.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/vcnl4000.c

@@ -61,6 +61,7 @@
 
 #define VCNL4200_AL_CONF	0x00 /* Ambient light configuration */
 #define VCNL4200_PS_CONF1	0x03 /* Proximity configuration */
+#define VCNL4200_PS_CONF3	0x04 /* Proximity configuration */
 #define VCNL4040_PS_THDL_LM	0x06 /* Proximity threshold low */
 #define VCNL4040_PS_THDH_LM	0x07 /* Proximity threshold high */
 #define VCNL4040_ALS_THDL_LM	0x02 /* Ambient light threshold low */
@@ -90,6 +91,7 @@
 #define VCNL4040_PS_CONF2_PS_IT	GENMASK(3, 1) /* Proximity integration time */
 #define VCNL4040_CONF1_PS_PERS	GENMASK(5, 4) /* Proximity interrupt persistence setting */
 #define VCNL4040_PS_CONF2_PS_INT	GENMASK(9, 8) /* Proximity interrupt mode */
+#define VCNL4040_PS_CONF3_MPS		GENMASK(6, 5) /* Proximity multi pulse number */
 #define VCNL4040_PS_IF_AWAY		BIT(8) /* Proximity event cross low threshold */
 #define VCNL4040_PS_IF_CLOSE		BIT(9) /* Proximity event cross high threshold */
 #define VCNL4040_ALS_RISING		BIT(12) /* Ambient Light cross high threshold */
@@ -158,6 +160,7 @@ static const int vcnl4200_als_it_times[][2] = {
 
 static const int vcnl4040_als_persistence[] = {1, 2, 4, 8};
 static const int vcnl4040_ps_persistence[] = {1, 2, 3, 4};
+static const int vcnl4040_ps_oversampling_ratio[] = {1, 2, 4, 8};
 
 #define VCNL4000_SLEEP_DELAY_MS	2000 /* before we enter pm_runtime_suspend */
 
@@ -770,6 +773,53 @@ static ssize_t vcnl4040_write_ps_period(struct vcnl4000_data *data, int val, int
 	return ret;
 }
 
+static ssize_t vcnl4040_read_ps_oversampling_ratio(struct vcnl4000_data *data, int *val)
+{
+	int ret;
+
+	ret = i2c_smbus_read_word_data(data->client, VCNL4200_PS_CONF3);
+	if (ret < 0)
+		return ret;
+
+	ret = FIELD_GET(VCNL4040_PS_CONF3_MPS, ret);
+	if (ret >= ARRAY_SIZE(vcnl4040_ps_oversampling_ratio))
+		return -EINVAL;
+
+	*val = vcnl4040_ps_oversampling_ratio[ret];
+
+	return ret;
+}
+
+static ssize_t vcnl4040_write_ps_oversampling_ratio(struct vcnl4000_data *data, int val)
+{
+	unsigned int i;
+	int ret;
+	u16 regval;
+
+	for (i = 0; i < ARRAY_SIZE(vcnl4040_ps_oversampling_ratio); i++) {
+		if (val == vcnl4040_ps_oversampling_ratio[i])
+			break;
+	}
+
+	if (i >= ARRAY_SIZE(vcnl4040_ps_oversampling_ratio))
+		return -EINVAL;
+
+	mutex_lock(&data->vcnl4000_lock);
+
+	ret = i2c_smbus_read_word_data(data->client, VCNL4200_PS_CONF3);
+	if (ret < 0)
+		goto out_unlock;
+
+	regval = FIELD_PREP(VCNL4040_PS_CONF3_MPS, i);
+	regval |= (ret & ~VCNL4040_PS_CONF3_MPS);
+	ret = i2c_smbus_write_word_data(data->client, VCNL4200_PS_CONF3,
+					regval);
+
+out_unlock:
+	mutex_unlock(&data->vcnl4000_lock);
+	return ret;
+}
+
 static int vcnl4000_read_raw(struct iio_dev *indio_dev,
 				struct iio_chan_spec const *chan,
 				int *val, int *val2, long mask)
@@ -820,6 +870,16 @@ static int vcnl4000_read_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		switch (chan->type) {
+		case IIO_PROXIMITY:
+			ret = vcnl4040_read_ps_oversampling_ratio(data, val);
+			if (ret < 0)
+				return ret;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
 	default:
 		return -EINVAL;
 	}
@@ -843,6 +903,13 @@ static int vcnl4040_write_raw(struct iio_dev *indio_dev,
 		default:
 			return -EINVAL;
 		}
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		switch (chan->type) {
+		case IIO_PROXIMITY:
+			return vcnl4040_write_ps_oversampling_ratio(data, val);
+		default:
+			return -EINVAL;
+		}
 	default:
 		return -EINVAL;
 	}
@@ -871,6 +938,16 @@ static int vcnl4040_read_avail(struct iio_dev *indio_dev,
 		}
 		*type = IIO_VAL_INT_PLUS_MICRO;
 		return IIO_AVAIL_LIST;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		switch (chan->type) {
+		case IIO_PROXIMITY:
+			*vals = (int *)vcnl4040_ps_oversampling_ratio;
+			*length = ARRAY_SIZE(vcnl4040_ps_oversampling_ratio);
+			*type = IIO_VAL_INT;
+			return IIO_AVAIL_LIST;
+		default:
+			return -EINVAL;
+		}
 	default:
 		return -EINVAL;
 	}
@@ -1643,8 +1720,10 @@ static const struct iio_chan_spec vcnl4040_channels[] = {
 	}, {
 		.type = IIO_PROXIMITY,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
-			BIT(IIO_CHAN_INFO_INT_TIME),
-		.info_mask_separate_available = BIT(IIO_CHAN_INFO_INT_TIME),
+			BIT(IIO_CHAN_INFO_INT_TIME) |
+			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+		.info_mask_separate_available = BIT(IIO_CHAN_INFO_INT_TIME) |
+			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
 		.ext_info = vcnl4000_ext_info,
 		.event_spec = vcnl4040_event_spec,
 		.num_event_specs = ARRAY_SIZE(vcnl4040_event_spec),