| Message ID | 20210422033841.22211-1-digetx@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] iio: gyro: mpu3050: Fix reported temperature value | expand |
22.04.2021 09:46, Andy Shevchenko пишет: > case IIO_TEMP: > - /* The temperature scaling is (x+23000)/280 > Celsius */ > + /* > + * The temperature scaling is (x+23000)/280 > Celsius, > + * where 23000 includes room temperature > offset of > + * +35C, 280 is the precision scale and x is > the 16-bit > + * signed integer which corresponds to the > temperature > + * range of -40C..85C. > > > > Datasheet says typical -30°... also think about the other comment you > gave, I.e. about temperature of the die itself. Are you suggesting that > at -40° the die T is also -40°? Does it have perpetuum mobile ? ;) it > might dissipate not to much energy, but we don’t know the linearity of > the curve there. My understanding that -40C is the minimum temperature which sensor may report. Alright, I think the comment could be improved a tad anyways. I'll prepare v3, thanks.
diff --git a/drivers/iio/gyro/mpu3050-core.c b/drivers/iio/gyro/mpu3050-core.c index ac90be03332a..ce9d1d3687f5 100644 --- a/drivers/iio/gyro/mpu3050-core.c +++ b/drivers/iio/gyro/mpu3050-core.c @@ -272,7 +272,16 @@ static int mpu3050_read_raw(struct iio_dev *indio_dev, case IIO_CHAN_INFO_OFFSET: switch (chan->type) { case IIO_TEMP: - /* The temperature scaling is (x+23000)/280 Celsius */ + /* + * The temperature scaling is (x+23000)/280 Celsius, + * where 23000 includes room temperature offset of + * +35C, 280 is the precision scale and x is the 16-bit + * signed integer which corresponds to the temperature + * range of -40C..85C. + * + * Temperature value itself represents temperature of + * the sensor die. + */ *val = 23000; return IIO_VAL_INT; default: @@ -329,7 +338,7 @@ static int mpu3050_read_raw(struct iio_dev *indio_dev, goto out_read_raw_unlock; } - *val = be16_to_cpu(raw_val); + *val = (s16)be16_to_cpu(raw_val); ret = IIO_VAL_INT; goto out_read_raw_unlock;
The raw temperature value is a 16-bit signed integer. The sign casting is missing in the code, which results in a wrong temperature reported by userspace tools, fix it. Cc: stable@vger.kernel.org Fixes: 3904b28efb2c ("iio: gyro: Add driver for the MPU-3050 gyroscope") Datasheet: https://www.cdiweb.com/datasheets/invensense/mpu-3000a.pdf Tested-by: Maxim Schwalm <maxim.schwalm@gmail.com> # Asus TF700T Tested-by: Svyatoslav Ryhel <clamor95@gmail.com> # Asus TF201 Reported-by: Svyatoslav Ryhel <clamor95@gmail.com> Reviewed-by: Andy Shevchenko <Andy.Shevchenko@gmail.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Dmitry Osipenko <digetx@gmail.com> --- Changelog: v2: - Replaced "signed 16bit integer" wording with "16-bit signed integer", replaced "Link" tag with the "Datasheet" and added "Fixes" tag as was suggested by Andy Shevchenko. - Added r-b from Andy Shevchenko and Linus Walleij. drivers/iio/gyro/mpu3050-core.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)