[PATCH] iio: imu: inv_icm45600: fix temperature offset reporting

[PATCH] iio: imu: inv_icm45600: fix temperature offset reporting

[Jean-Baptiste Maneyrol via B4 Relay]

From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>

Correct temperature computation is (raw + offset) * scale and not
apply scale and offset afterward.
Fix temperature offset reporting to the correct value and update
commentaries for the new computation.

Fixes: 27e072bc34d1 ("iio: imu: inv_icm45600: add IMU IIO gyroscope device")

Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Cc: stable@vger.kernel.org
---
 drivers/iio/imu/inv_icm45600/inv_icm45600_core.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/imu/inv_icm45600/inv_icm45600_core.c b/drivers/iio/imu/inv_icm45600/inv_icm45600_core.c
index ab1cb7b9dba435a3280e50ab77cd16e903c7816c..25bd9757a594d0180d7f53b49f959a49a50c64a9 100644
--- a/drivers/iio/imu/inv_icm45600/inv_icm45600_core.c
+++ b/drivers/iio/imu/inv_icm45600/inv_icm45600_core.c
@@ -960,16 +960,17 @@ int inv_icm45600_temp_read_raw(struct iio_dev *indio_dev,
 		return IIO_VAL_INT;
 	/*
 	 * T°C = (temp / 128) + 25
-	 * Tm°C = 1000 * ((temp * 100 / 12800) + 25)
-	 * scale: 100000 / 13248 = 7.8125
-	 * offset: 25000
+	 * Tm°C = ((temp + 25 * 128) / 128)) * 1000
+	 * Tm°C = (temp + 3200) * (1000 / 128)
+	 * scale: 1000 / 128 = 7.8125
+	 * offset: 3200
 	 */
 	case IIO_CHAN_INFO_SCALE:
 		*val = 7;
 		*val2 = 812500;
 		return IIO_VAL_INT_PLUS_MICRO;
 	case IIO_CHAN_INFO_OFFSET:
-		*val = 25000;
+		*val = 3200;
 		return IIO_VAL_INT;
 	default:
 		return -EINVAL;

---
base-commit: a7b10f0963c651a6406d958a5f64b9c5594f84da
change-id: 20251218-inv-icm45600-fix-temperature-offset-reporting-190a09adfdad

Best regards,
-- 
Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>

Re: [PATCH] iio: imu: inv_icm45600: fix temperature offset reporting

[Jonathan Cameron]

On Thu, 18 Dec 2025 11:30:59 +0100
Jean-Baptiste Maneyrol via B4 Relay <devnull+jean-baptiste.maneyrol.tdk.com@kernel.org> wrote:

> From: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
> 
> Correct temperature computation is (raw + offset) * scale and not
> apply scale and offset afterward.
> Fix temperature offset reporting to the correct value and update
> commentaries for the new computation.
> 
> Fixes: 27e072bc34d1 ("iio: imu: inv_icm45600: add IMU IIO gyroscope device")
> 
No blank line here.  That breaks a bunch of scripts and is checked for
in upstream trees so with the line break this would be rejected.
> Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
> Cc: stable@vger.kernel.org
Applied to the fixes-togreg tree.

Thanks,

Jonathan

> ---
>  drivers/iio/imu/inv_icm45600/inv_icm45600_core.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/imu/inv_icm45600/inv_icm45600_core.c b/drivers/iio/imu/inv_icm45600/inv_icm45600_core.c
> index ab1cb7b9dba435a3280e50ab77cd16e903c7816c..25bd9757a594d0180d7f53b49f959a49a50c64a9 100644
> --- a/drivers/iio/imu/inv_icm45600/inv_icm45600_core.c
> +++ b/drivers/iio/imu/inv_icm45600/inv_icm45600_core.c
> @@ -960,16 +960,17 @@ int inv_icm45600_temp_read_raw(struct iio_dev *indio_dev,
>  		return IIO_VAL_INT;
>  	/*
>  	 * T°C = (temp / 128) + 25
> -	 * Tm°C = 1000 * ((temp * 100 / 12800) + 25)
> -	 * scale: 100000 / 13248 = 7.8125
> -	 * offset: 25000
> +	 * Tm°C = ((temp + 25 * 128) / 128)) * 1000
> +	 * Tm°C = (temp + 3200) * (1000 / 128)
> +	 * scale: 1000 / 128 = 7.8125
> +	 * offset: 3200
>  	 */
>  	case IIO_CHAN_INFO_SCALE:
>  		*val = 7;
>  		*val2 = 812500;
>  		return IIO_VAL_INT_PLUS_MICRO;
>  	case IIO_CHAN_INFO_OFFSET:
> -		*val = 25000;
> +		*val = 3200;
>  		return IIO_VAL_INT;
>  	default:
>  		return -EINVAL;
> 
> ---
> base-commit: a7b10f0963c651a6406d958a5f64b9c5594f84da
> change-id: 20251218-inv-icm45600-fix-temperature-offset-reporting-190a09adfdad
> 
> Best regards,