iio: pressure: bmp280: add ability to control oversampling rate

This adds ability to control the oversampling ratio of the temperature
and pressure measurement for both bmp180 and bmp280.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Vlad Dogaru <vlad.dogaru@intel.com>
Cc: Christoph Mair <christoph.mair@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/pressure/bmp280.c

@@ -48,19 +48,21 @@
 
 #define BMP280_OSRS_TEMP_MASK		(BIT(7) | BIT(6) | BIT(5))
 #define BMP280_OSRS_TEMP_SKIP		0
-#define BMP280_OSRS_TEMP_1X		BIT(5)
-#define BMP280_OSRS_TEMP_2X		BIT(6)
-#define BMP280_OSRS_TEMP_4X		(BIT(6) | BIT(5))
-#define BMP280_OSRS_TEMP_8X		BIT(7)
-#define BMP280_OSRS_TEMP_16X		(BIT(7) | BIT(5))
+#define BMP280_OSRS_TEMP_X(osrs_t)	((osrs_t) << 5)
+#define BMP280_OSRS_TEMP_1X		BMP280_OSRS_TEMP_X(1)
+#define BMP280_OSRS_TEMP_2X		BMP280_OSRS_TEMP_X(2)
+#define BMP280_OSRS_TEMP_4X		BMP280_OSRS_TEMP_X(3)
+#define BMP280_OSRS_TEMP_8X		BMP280_OSRS_TEMP_X(4)
+#define BMP280_OSRS_TEMP_16X		BMP280_OSRS_TEMP_X(5)
 
 #define BMP280_OSRS_PRESS_MASK		(BIT(4) | BIT(3) | BIT(2))
 #define BMP280_OSRS_PRESS_SKIP		0
-#define BMP280_OSRS_PRESS_1X		BIT(2)
-#define BMP280_OSRS_PRESS_2X		BIT(3)
-#define BMP280_OSRS_PRESS_4X		(BIT(3) | BIT(2))
-#define BMP280_OSRS_PRESS_8X		BIT(4)
-#define BMP280_OSRS_PRESS_16X		(BIT(4) | BIT(2))
+#define BMP280_OSRS_PRESS_X(osrs_p)	((osrs_p) << 2)
+#define BMP280_OSRS_PRESS_1X		BMP280_OSRS_PRESS_X(1)
+#define BMP280_OSRS_PRESS_2X		BMP280_OSRS_PRESS_X(2)
+#define BMP280_OSRS_PRESS_4X		BMP280_OSRS_PRESS_X(3)
+#define BMP280_OSRS_PRESS_8X		BMP280_OSRS_PRESS_X(4)
+#define BMP280_OSRS_PRESS_16X		BMP280_OSRS_PRESS_X(5)
 
 #define BMP280_MODE_MASK		(BIT(1) | BIT(0))
 #define BMP280_MODE_SLEEP		0
@@ -98,6 +100,10 @@ struct bmp280_data {
 	struct regmap *regmap;
 	const struct bmp280_chip_info *chip_info;
 
+	/* log of base 2 of oversampling rate */
+	u8 oversampling_press;
+	u8 oversampling_temp;
+
 	/*
 	 * Carryover value from temperature conversion, used in pressure
 	 * calculation.
@@ -108,6 +114,12 @@ struct bmp280_data {
 struct bmp280_chip_info {
 	const struct regmap_config *regmap_config;
 
+	const int *oversampling_temp_avail;
+	int num_oversampling_temp_avail;
+
+	const int *oversampling_press_avail;
+	int num_oversampling_press_avail;
+
 	int (*chip_config)(struct bmp280_data *);
 	int (*read_temp)(struct bmp280_data *, int *);
 	int (*read_press)(struct bmp280_data *, int *, int *);
@@ -123,11 +135,13 @@ enum { P1, P2, P3, P4, P5, P6, P7, P8, P9 };
 static const struct iio_chan_spec bmp280_channels[] = {
 	{
 		.type = IIO_PRESSURE,
-		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
+				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
 	},
 	{
 		.type = IIO_TEMP,
-		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
+				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
 	},
 };
 
@@ -333,6 +347,21 @@ static int bmp280_read_raw(struct iio_dev *indio_dev,
 			break;
 		}
 		break;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			*val = 1 << data->oversampling_press;
+			ret = IIO_VAL_INT;
+			break;
+		case IIO_TEMP:
+			*val = 1 << data->oversampling_temp;
+			ret = IIO_VAL_INT;
+			break;
+		default:
+			ret = -EINVAL;
+			break;
+		}
+		break;
 	default:
 		ret = -EINVAL;
 		break;
@@ -343,22 +372,135 @@ static int bmp280_read_raw(struct iio_dev *indio_dev,
 	return ret;
 }
 
+static int bmp280_write_oversampling_ratio_temp(struct bmp280_data *data,
+					       int val)
+{
+	int i;
+	const int *avail = data->chip_info->oversampling_temp_avail;
+	const int n = data->chip_info->num_oversampling_temp_avail;
+
+	for (i = 0; i < n; i++) {
+		if (avail[i] == val) {
+			data->oversampling_temp = ilog2(val);
+
+			return data->chip_info->chip_config(data);
+		}
+	}
+	return -EINVAL;
+}
+
+static int bmp280_write_oversampling_ratio_press(struct bmp280_data *data,
+					       int val)
+{
+	int i;
+	const int *avail = data->chip_info->oversampling_press_avail;
+	const int n = data->chip_info->num_oversampling_press_avail;
+
+	for (i = 0; i < n; i++) {
+		if (avail[i] == val) {
+			data->oversampling_press = ilog2(val);
+
+			return data->chip_info->chip_config(data);
+		}
+	}
+	return -EINVAL;
+}
+
+static int bmp280_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int val, int val2, long mask)
+{
+	int ret = 0;
+	struct bmp280_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		mutex_lock(&data->lock);
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			ret = bmp280_write_oversampling_ratio_press(data, val);
+			break;
+		case IIO_TEMP:
+			ret = bmp280_write_oversampling_ratio_temp(data, val);
+			break;
+		default:
+			ret = -EINVAL;
+			break;
+		}
+		mutex_unlock(&data->lock);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static ssize_t bmp280_show_avail(char *buf, const int *vals, const int n)
+{
+	size_t len = 0;
+	int i;
+
+	for (i = 0; i < n; i++)
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%d ", vals[i]);
+
+	buf[len - 1] = '\n';
+
+	return len;
+}
+
+static ssize_t bmp280_show_temp_oversampling_avail(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct bmp280_data *data = iio_priv(dev_to_iio_dev(dev));
+
+	return bmp280_show_avail(buf, data->chip_info->oversampling_temp_avail,
+				 data->chip_info->num_oversampling_temp_avail);
+}
+
+static ssize_t bmp280_show_press_oversampling_avail(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct bmp280_data *data = iio_priv(dev_to_iio_dev(dev));
+
+	return bmp280_show_avail(buf, data->chip_info->oversampling_press_avail,
+				 data->chip_info->num_oversampling_press_avail);
+}
+
+static IIO_DEVICE_ATTR(in_temp_oversampling_ratio_available,
+	S_IRUGO, bmp280_show_temp_oversampling_avail, NULL, 0);
+
+static IIO_DEVICE_ATTR(in_pressure_oversampling_ratio_available,
+	S_IRUGO, bmp280_show_press_oversampling_avail, NULL, 0);
+
+static struct attribute *bmp280_attributes[] = {
+	&iio_dev_attr_in_temp_oversampling_ratio_available.dev_attr.attr,
+	&iio_dev_attr_in_pressure_oversampling_ratio_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group bmp280_attrs_group = {
+	.attrs = bmp280_attributes,
+};
+
 static const struct iio_info bmp280_info = {
 	.driver_module = THIS_MODULE,
 	.read_raw = &bmp280_read_raw,
+	.write_raw = &bmp280_write_raw,
+	.attrs = &bmp280_attrs_group,
 };
 
 static int bmp280_chip_config(struct bmp280_data *data)
 {
 	int ret;
+	u8 osrs = BMP280_OSRS_TEMP_X(data->oversampling_temp + 1) |
+		  BMP280_OSRS_PRESS_X(data->oversampling_press + 1);
 
 	ret = regmap_update_bits(data->regmap, BMP280_REG_CTRL_MEAS,
 				 BMP280_OSRS_TEMP_MASK |
 				 BMP280_OSRS_PRESS_MASK |
 				 BMP280_MODE_MASK,
-				 BMP280_OSRS_TEMP_2X |
-				 BMP280_OSRS_PRESS_16X |
-				 BMP280_MODE_NORMAL);
+				 osrs | BMP280_MODE_NORMAL);
 	if (ret < 0) {
 		dev_err(&data->client->dev,
 			"failed to write ctrl_meas register\n");
@@ -377,8 +519,17 @@ static int bmp280_chip_config(struct bmp280_data *data)
 	return ret;
 }
 
+static const int bmp280_oversampling_avail[] = { 1, 2, 4, 8, 16 };
+
 static const struct bmp280_chip_info bmp280_chip_info = {
 	.regmap_config = &bmp280_regmap_config,
+
+	.oversampling_temp_avail = bmp280_oversampling_avail,
+	.num_oversampling_temp_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
+	.oversampling_press_avail = bmp280_oversampling_avail,
+	.num_oversampling_press_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
 	.chip_config = bmp280_chip_config,
 	.read_temp = bmp280_read_temp,
 	.read_press = bmp280_read_press,
@@ -433,7 +584,7 @@ static int bmp180_measure(struct bmp280_data *data, u8 ctrl_meas)
 	if (ctrl_meas == BMP180_MEAS_TEMP)
 		delay_us = 4500;
 	else
-		delay_us = conversion_time_max[ilog2(8)];
+		delay_us = conversion_time_max[data->oversampling_press];
 
 	usleep_range(delay_us, delay_us + 1000);
 
@@ -573,7 +724,7 @@ static int bmp180_read_adc_press(struct bmp280_data *data, int *val)
 {
 	int ret;
 	__be32 tmp = 0;
-	u8 oss = ilog2(8);
+	u8 oss = data->oversampling_press;
 
 	ret = bmp180_measure(data, BMP180_MEAS_PRESS_X(oss));
 	if (ret)
@@ -599,7 +750,7 @@ static u32 bmp180_compensate_press(struct bmp280_data *data, s32 adc_press)
 	s32 x1, x2, x3, p;
 	s32 b3, b6;
 	u32 b4, b7;
-	s32 oss = ilog2(8);
+	s32 oss = data->oversampling_press;
 	struct bmp180_calib calib;
 
 	ret = bmp180_read_calib(data, &calib);
@@ -660,8 +811,20 @@ static int bmp180_chip_config(struct bmp280_data *data)
 	return 0;
 }
 
+static const int bmp180_oversampling_temp_avail[] = { 1 };
+static const int bmp180_oversampling_press_avail[] = { 1, 2, 4, 8 };
+
 static const struct bmp280_chip_info bmp180_chip_info = {
 	.regmap_config = &bmp180_regmap_config,
+
+	.oversampling_temp_avail = bmp180_oversampling_temp_avail,
+	.num_oversampling_temp_avail =
+		ARRAY_SIZE(bmp180_oversampling_temp_avail),
+
+	.oversampling_press_avail = bmp180_oversampling_press_avail,
+	.num_oversampling_press_avail =
+		ARRAY_SIZE(bmp180_oversampling_press_avail),
+
 	.chip_config = bmp180_chip_config,
 	.read_temp = bmp180_read_temp,
 	.read_press = bmp180_read_press,
@@ -693,9 +856,13 @@ static int bmp280_probe(struct i2c_client *client,
 	switch (id->driver_data) {
 	case BMP180_CHIP_ID:
 		data->chip_info = &bmp180_chip_info;
+		data->oversampling_press = ilog2(8);
+		data->oversampling_temp = ilog2(1);
 		break;
 	case BMP280_CHIP_ID:
 		data->chip_info = &bmp280_chip_info;
+		data->oversampling_press = ilog2(16);
+		data->oversampling_temp = ilog2(2);
 		break;
 	default:
 		return -EINVAL;