iio: magn: bmc150_magn: add oversampling ratio

Export the oversampling ratio so that the user can change the
number of repetions for x/y/z axis.

The sampling frequency is limited by the oversampling ratio.
The available sampling frequencies might change depending
on the values of oversampling_ratio.

The specification can be downloaded from:
http://ae-bst.resource.bosch.com/media/products/dokumente/bmc150/BST-BMC150-DS000-04.pdf.
Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/magnetometer/bmc150_magn.c

@@ -146,6 +146,7 @@ struct bmc150_magn_data {
 	s32 buffer[6];
 	struct iio_trigger *dready_trig;
 	bool dready_trigger_on;
+	int max_odr;
 };
 
 static const struct {
@@ -323,6 +324,43 @@ static int bmc150_magn_set_odr(struct bmc150_magn_data *data, int val)
 	return -EINVAL;
 }
 
+static int bmc150_magn_set_max_odr(struct bmc150_magn_data *data, int rep_xy,
+				   int rep_z, int odr)
+{
+	int ret, reg_val, max_odr;
+
+	if (rep_xy <= 0) {
+		ret = regmap_read(data->regmap, BMC150_MAGN_REG_REP_XY,
+				  &reg_val);
+		if (ret < 0)
+			return ret;
+		rep_xy = BMC150_MAGN_REGVAL_TO_REPXY(reg_val);
+	}
+	if (rep_z <= 0) {
+		ret = regmap_read(data->regmap, BMC150_MAGN_REG_REP_Z,
+				  &reg_val);
+		if (ret < 0)
+			return ret;
+		rep_z = BMC150_MAGN_REGVAL_TO_REPZ(reg_val);
+	}
+	if (odr <= 0) {
+		ret = bmc150_magn_get_odr(data, &odr);
+		if (ret < 0)
+			return ret;
+	}
+	/* the maximum selectable read-out frequency from datasheet */
+	max_odr = 1000000 / (145 * rep_xy + 500 * rep_z + 980);
+	if (odr > max_odr) {
+		dev_err(&data->client->dev,
+			"Can't set oversampling with sampling freq %d\n",
+			odr);
+		return -EINVAL;
+	}
+	data->max_odr = max_odr;
+
+	return 0;
+}
+
 static s32 bmc150_magn_compensate_x(struct bmc150_magn_trim_regs *tregs, s16 x,
 				    u16 rhall)
 {
@@ -422,7 +460,7 @@ static int bmc150_magn_read_raw(struct iio_dev *indio_dev,
 				int *val, int *val2, long mask)
 {
 	struct bmc150_magn_data *data = iio_priv(indio_dev);
-	int ret;
+	int ret, tmp;
 	s32 values[AXIS_XYZ_MAX];
 
 	switch (mask) {
@@ -467,6 +505,26 @@ static int bmc150_magn_read_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		switch (chan->channel2) {
+		case IIO_MOD_X:
+		case IIO_MOD_Y:
+			ret = regmap_read(data->regmap, BMC150_MAGN_REG_REP_XY,
+					  &tmp);
+			if (ret < 0)
+				return ret;
+			*val = BMC150_MAGN_REGVAL_TO_REPXY(tmp);
+			return IIO_VAL_INT;
+		case IIO_MOD_Z:
+			ret = regmap_read(data->regmap, BMC150_MAGN_REG_REP_Z,
+					  &tmp);
+			if (ret < 0)
+				return ret;
+			*val = BMC150_MAGN_REGVAL_TO_REPZ(tmp);
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
 	default:
 		return -EINVAL;
 	}
@@ -481,10 +539,50 @@ static int bmc150_magn_write_raw(struct iio_dev *indio_dev,
 
 	switch (mask) {
 	case IIO_CHAN_INFO_SAMP_FREQ:
+		if (val > data->max_odr)
+			return -EINVAL;
 		mutex_lock(&data->mutex);
 		ret = bmc150_magn_set_odr(data, val);
 		mutex_unlock(&data->mutex);
 		return ret;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		switch (chan->channel2) {
+		case IIO_MOD_X:
+		case IIO_MOD_Y:
+			if (val < 1 || val > 511)
+				return -EINVAL;
+			mutex_lock(&data->mutex);
+			ret = bmc150_magn_set_max_odr(data, val, 0, 0);
+			if (ret < 0) {
+				mutex_unlock(&data->mutex);
+				return ret;
+			}
+			ret = regmap_update_bits(data->regmap,
+						 BMC150_MAGN_REG_REP_XY,
+						 0xFF,
+						 BMC150_MAGN_REPXY_TO_REGVAL
+						 (val));
+			mutex_unlock(&data->mutex);
+			return ret;
+		case IIO_MOD_Z:
+			if (val < 1 || val > 256)
+				return -EINVAL;
+			mutex_lock(&data->mutex);
+			ret = bmc150_magn_set_max_odr(data, 0, val, 0);
+			if (ret < 0) {
+				mutex_unlock(&data->mutex);
+				return ret;
+			}
+			ret = regmap_update_bits(data->regmap,
+						 BMC150_MAGN_REG_REP_Z,
+						 0xFF,
+						 BMC150_MAGN_REPZ_TO_REGVAL
+						 (val));
+			mutex_unlock(&data->mutex);
+			return ret;
+		default:
+			return -EINVAL;
+		}
 	default:
 		return -EINVAL;
 	}
@@ -501,10 +599,31 @@ static int bmc150_magn_validate_trigger(struct iio_dev *indio_dev,
 	return 0;
 }
 
-static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("2 6 8 10 15 20 25 30");
+static ssize_t bmc150_magn_show_samp_freq_avail(struct device *dev,
+						struct device_attribute *attr,
+						char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct bmc150_magn_data *data = iio_priv(indio_dev);
+	size_t len = 0;
+	u8 i;
+
+	for (i = 0; i < ARRAY_SIZE(bmc150_magn_samp_freq_table); i++) {
+		if (bmc150_magn_samp_freq_table[i].freq > data->max_odr)
+			break;
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%d ",
+				 bmc150_magn_samp_freq_table[i].freq);
+	}
+	/* replace last space with a newline */
+	buf[len - 1] = '\n';
+
+	return len;
+}
+
+static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(bmc150_magn_show_samp_freq_avail);
 
 static struct attribute *bmc150_magn_attributes[] = {
-	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
+	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
 	NULL,
 };
 
@@ -516,7 +635,8 @@ static const struct attribute_group bmc150_magn_attrs_group = {
 	.type = IIO_MAGN,						\
 	.modified = 1,							\
 	.channel2 = IIO_MOD_##_axis,					\
-	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
+			      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),	\
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ) |	\
 				    BIT(IIO_CHAN_INFO_SCALE),		\
 	.scan_index = AXIS_##_axis,					\
@@ -616,6 +736,11 @@ static int bmc150_magn_init(struct bmc150_magn_data *data)
 		goto err_poweroff;
 	}
 
+	ret = bmc150_magn_set_max_odr(data, preset.rep_xy, preset.rep_z,
+				      preset.odr);
+	if (ret < 0)
+		goto err_poweroff;
+
 	ret = bmc150_magn_set_power_mode(data, BMC150_MAGN_POWER_MODE_NORMAL,
 					 true);
 	if (ret < 0) {