From: Gwendal Grignou gwendal@chromium.org
commit 3d02d7082e5823598090530c3988a35f69689943 upstream.
Calculation did not use IIO_DEGREE_TO_RAD and implemented a variant to avoid precision loss as we aim a nano value. The offset added to avoid rounding error, though, doesn't give us a close result to the expected value. E.g.
For 1000dps, the result should be:
(1000 * pi ) / 180 >> 15 ~= 0.000532632218
But with current calculation we get
$ cat scale 0.000547890
Fix the calculation by just doing the maths involved for a nano value
val * pi * 10e12 / (180 * 2^15)
so we get a closer result.
$ cat scale 0.000532632
Fixes: c14dca07a31d ("iio: cros_ec_sensors: add ChromeOS EC Contiguous Sensors driver") Signed-off-by: Gwendal Grignou gwendal@chromium.org Signed-off-by: Enric Balletbo i Serra enric.balletbo@collabora.com Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
--- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c +++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c @@ -103,9 +103,10 @@ static int cros_ec_sensors_read(struct i * Do not use IIO_DEGREE_TO_RAD to avoid precision * loss. Round to the nearest integer. */ - *val = div_s64(val64 * 314159 + 9000000ULL, 1000); - *val2 = 18000 << (CROS_EC_SENSOR_BITS - 1); - ret = IIO_VAL_FRACTIONAL; + *val = 0; + *val2 = div_s64(val64 * 3141592653ULL, + 180 << (CROS_EC_SENSOR_BITS - 1)); + ret = IIO_VAL_INT_PLUS_NANO; break; case MOTIONSENSE_TYPE_MAG: /*