projects / thirdparty / kernel / stable-queue.git / blame
| Commit | Line | Data |
|---|---|---|
| 21cf661e GKH |
1 | From 3d02d7082e5823598090530c3988a35f69689943 Mon Sep 17 00:00:00 2001 |
| 2 | From: Gwendal Grignou <gwendal@chromium.org> | |
| 3 | Date: Wed, 13 Mar 2019 12:40:02 +0100 | |
| 4 | Subject: iio: cros_ec: Fix the maths for gyro scale calculation | |
| 5 | ||
| 6 | From: Gwendal Grignou <gwendal@chromium.org> | |
| 7 | ||
| 8 | commit 3d02d7082e5823598090530c3988a35f69689943 upstream. | |
| 9 | ||
| 10 | Calculation did not use IIO_DEGREE_TO_RAD and implemented a variant to | |
| 11 | avoid precision loss as we aim a nano value. The offset added to avoid | |
| 12 | rounding error, though, doesn't give us a close result to the expected | |
| 13 | value. E.g. | |
| 14 | ||
| 15 | For 1000dps, the result should be: | |
| 16 | ||
| 17 | (1000 * pi ) / 180 >> 15 ~= 0.000532632218 | |
| 18 | ||
| 19 | But with current calculation we get | |
| 20 | ||
| 21 | $ cat scale | |
| 22 | 0.000547890 | |
| 23 | ||
| 24 | Fix the calculation by just doing the maths involved for a nano value | |
| 25 | ||
| 26 | val * pi * 10e12 / (180 * 2^15) | |
| 27 | ||
| 28 | so we get a closer result. | |
| 29 | ||
| 30 | $ cat scale | |
| 31 | 0.000532632 | |
| 32 | ||
| 33 | Fixes: c14dca07a31d ("iio: cros_ec_sensors: add ChromeOS EC Contiguous Sensors driver") | |
| 34 | Signed-off-by: Gwendal Grignou <gwendal@chromium.org> | |
| 35 | Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> | |
| 36 | Cc: <Stable@vger.kernel.org> | |
| 37 | Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> | |
| 38 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> | |
| 39 | ||
| 40 | --- | |
| 41 | drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c | 7 ++++--- | |
| 42 | 1 file changed, 4 insertions(+), 3 deletions(-) | |
| 43 | ||
| 44 | --- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c | |
| 45 | +++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors.c | |
| 46 | @@ -104,9 +104,10 @@ static int cros_ec_sensors_read(struct i | |
| 47 | * Do not use IIO_DEGREE_TO_RAD to avoid precision | |
| 48 | * loss. Round to the nearest integer. | |
| 49 | */ | |
| 50 | - *val = div_s64(val64 * 314159 + 9000000ULL, 1000); | |
| 51 | - *val2 = 18000 << (CROS_EC_SENSOR_BITS - 1); | |
| 52 | - ret = IIO_VAL_FRACTIONAL; | |
| 53 | + *val = 0; | |
| 54 | + *val2 = div_s64(val64 * 3141592653ULL, | |
| 55 | + 180 << (CROS_EC_SENSOR_BITS - 1)); | |
| 56 | + ret = IIO_VAL_INT_PLUS_NANO; | |
| 57 | break; | |
| 58 | case MOTIONSENSE_TYPE_MAG: | |
| 59 | /* |