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| author |   Gwendal Grignou <gwendal@chromium.org> | 2019-03-13 12:40:02 +0100 |
|---|---|---|
| committer |   Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2019-03-16 16:08:55 +0000 |
| commit | 3d02d7082e5823598090530c3988a35f69689943 (patch) | |
| tree | 1ffcb16eb7ce2e3a5badc8dfa6e703ed980fc385 /drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c | |
| parent | iio: adc: xilinx: prevent touching unclocked h/w on remove (diff) | |
| download | linux-dev-3d02d7082e5823598090530c3988a35f69689943.tar.xz linux-dev-3d02d7082e5823598090530c3988a35f69689943.zip | |
iio: cros_ec: Fix the maths for gyro scale calculation
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>
Diffstat (limited to 'drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c')
| -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 89cb0066a6e0..8d76afb87d87 100644 --- 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 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: /* |