diff options
| author | Gwendal Grignou <gwendal@chromium.org> | 2019-03-13 12:40:02 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-04-27 09:35:35 +0200 |
| commit | 0336305753a66205f0b74ab9c7236cd436238870 (patch) | |
| tree | 3b54adcc303c2db2980f942d49f072f684776153 /drivers/iio | |
| parent | f245ce44d58e88c74d37d73b23ac9617789038d2 (diff) | |
iio: cros_ec: Fix the maths for gyro scale calculation
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>
Diffstat (limited to 'drivers/iio')
| -rw-r--r-- | drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c index 38e8783e4b05..287fbe08264d 100644 --- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c +++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c @@ -104,9 +104,10 @@ static int cros_ec_sensors_read(struct iio_dev *indio_dev, * 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: /* |