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Commit c2890547 authored by Daniel Baluta's avatar Daniel Baluta Committed by Jonathan Cameron
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iio: magnetometer: mmc35240: Fix broken processed value 



The current computation for fractional part of the magnetic
field is broken. This patch fixes it by taking a different
approach. We expose the raw reading in milli Gauss (to avoid
rounding errors) with a scale of 0.001.

Thus the final computation is done in userspace where floating
point operation are more relaxed.

Fixes: abeb6b1e ("iio: magnetometer: Add support for MEMSIC MMC35240")
Signed-off-by: default avatarDaniel Baluta <daniel.baluta@intel.com>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent bd35a214

drivers/iio/magnetometer/mmc35240.c

+27 −16
Original line number Diff line number Diff line
@@ -113,8 +113,9 @@ static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("100 200 333 666"); 
	.modified = 1, \

	.channel2 = IIO_MOD_ ## _axis, \

	.address = AXIS_ ## _axis, \

	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \

	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ), \

	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \

	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ) | \

			BIT(IIO_CHAN_INFO_SCALE), \

}



static const struct iio_chan_spec mmc35240_channels[] = {
@@ -241,9 +242,19 @@ static int mmc35240_read_measurement(struct mmc35240_data *data, __le16 buf[3]) 
				3 * sizeof(__le16));

}



static int mmc35240_raw_to_gauss(struct mmc35240_data *data, int index,

				 __le16 buf[],

				 int *val, int *val2)

/**

 * mmc35240_raw_to_mgauss - convert raw readings to milli gauss. Also apply

			    compensation for output value.

 *

 * @data: device private data

 * @index: axis index for which we want the conversion

 * @buf: raw data to be converted, 2 bytes in little endian format

 * @val: compensated output reading (unit is milli gauss)

 *

 * Returns: 0 in case of success, -EINVAL when @index is not valid

 */

static int mmc35240_raw_to_mgauss(struct mmc35240_data *data, int index,

				  __le16 buf[], int *val)

{

	int raw_x, raw_y, raw_z;

	int sens_x, sens_y, sens_z;
@@ -261,18 +272,15 @@ static int mmc35240_raw_to_gauss(struct mmc35240_data *data, int index, 


	switch (index) {

	case AXIS_X:

		*val = (raw_x - nfo) / sens_x;

		*val2 = ((raw_x - nfo) % sens_x) * 1000000;

		*val = (raw_x - nfo) * 1000 / sens_x;

		break;

	case AXIS_Y:

		*val = (raw_y - nfo) / sens_y - (raw_z - nfo) / sens_z;

		*val2 = (((raw_y - nfo) % sens_y - (raw_z - nfo) % sens_z))

			* 1000000;

		*val = (raw_y - nfo) * 1000 / sens_y -

			(raw_z - nfo)  * 1000 / sens_z;

		break;

	case AXIS_Z:

		*val = (raw_y - nfo) / sens_y + (raw_z - nfo) / sens_z;

		*val2 = (((raw_y - nfo) % sens_y + (raw_z - nfo) % sens_z))

			* 1000000;

		*val = (raw_y - nfo) * 1000 / sens_y +

			(raw_z - nfo) * 1000 / sens_z;

		break;

	default:

		return -EINVAL;
@@ -290,16 +298,19 @@ static int mmc35240_read_raw(struct iio_dev *indio_dev, 
	__le16 buf[3];



	switch (mask) {

	case IIO_CHAN_INFO_PROCESSED:

	case IIO_CHAN_INFO_RAW:

		mutex_lock(&data->mutex);

		ret = mmc35240_read_measurement(data, buf);

		mutex_unlock(&data->mutex);

		if (ret < 0)

			return ret;

		ret = mmc35240_raw_to_gauss(data, chan->address,

					    buf, val, val2);

		ret = mmc35240_raw_to_mgauss(data, chan->address, buf, val);

		if (ret < 0)

			return ret;

		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:

		*val = 0;

		*val2 = 1000;

		return IIO_VAL_INT_PLUS_MICRO;

	case IIO_CHAN_INFO_SAMP_FREQ:

		mutex_lock(&data->mutex);