iio: mma8452: Use correct acceleration units.

The userspace interface for acceleration sensors is documented as using
m/s^2 units [Documentation/ABI/testing/sysfs-bus-iio]

The fullscale raw value for the mma8452 (-2048) corresponds to -2G, -4G or -8G
depending on the seleted mode.

The scale table was converting to G rather than m/s^2.
Change the scaling table to match the documented interface.

Signed-off-by: Martin Fuzzey <mfuzzey@parkeon.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Cc: stable@vger.kernel.org

diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
index 17aeea1705665f799990dd7ae69029c7cf09330c..2a5fa9a436e5cd2c7f495207717e0709774b8d48 100644 (file)
--- a/drivers/iio/accel/mma8452.c
+++ b/drivers/iio/accel/mma8452.c
@@ -111,8 +111,14 @@ static const int mma8452_samp_freq[8][2] = {
        {6, 250000}, {1, 560000}
 };
 
+/* 
+ * Hardware has fullscale of -2G, -4G, -8G corresponding to raw value -2048
+ * The userspace interface uses m/s^2 and we declare micro units
+ * So scale factor is given by:
+ *     g * N * 1000000 / 2048 for N = 2, 4, 8 and g=9.80665
+ */
 static const int mma8452_scales[3][2] = {
-       {0, 977}, {0, 1953}, {0, 3906}
+       {0, 9577}, {0, 19154}, {0, 38307}
 };
 
 static ssize_t mma8452_show_samp_freq_avail(struct device *dev,