From: Sean Nyekjaer <sean@geanix.com>
Date: Fri, 2 May 2025 09:37:26 +0000 (+0200)
Subject: iio: imu: inv_icm42600: Fix temperature calculation
X-Git-Tag: v6.16-rc1~30^2~35^2~4
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e2f820014239df9360064079ae93f838ff3b7f8c;p=thirdparty%2Flinux.git

iio: imu: inv_icm42600: Fix temperature calculation

>From the documentation:
"offset to be added to <type>[Y]_raw prior toscaling by <type>[Y]_scale"
Offset should be applied before multiplying scale, so divide offset by
scale to make this correct.

Fixes: bc3eb0207fb5 ("iio: imu: inv_icm42600: add temperature sensor support")
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
Acked-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Link: https://patch.msgid.link/20250502-imu-v1-1-129b8391a4e3@geanix.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---

diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_temp.c b/drivers/iio/imu/inv_icm42600/inv_icm42600_temp.c
index 213cce1c3111..91f0f381082b 100644
--- a/drivers/iio/imu/inv_icm42600/inv_icm42600_temp.c
+++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_temp.c
@@ -67,16 +67,18 @@ int inv_icm42600_temp_read_raw(struct iio_dev *indio_dev,
 		return IIO_VAL_INT;
 	/*
 	 * T°C = (temp / 132.48) + 25
-	 * Tm°C = 1000 * ((temp * 100 / 13248) + 25)
+	 * Tm°C = 1000 * ((temp / 132.48) + 25)
+	 * Tm°C = 7.548309 * temp + 25000
+	 * Tm°C = (temp + 3312) * 7.548309
 	 * scale: 100000 / 13248 ~= 7.548309
-	 * offset: 25000
+	 * offset: 3312
 	 */
 	case IIO_CHAN_INFO_SCALE:
 		*val = 7;
 		*val2 = 548309;
 		return IIO_VAL_INT_PLUS_MICRO;
 	case IIO_CHAN_INFO_OFFSET:
-		*val = 25000;
+		*val = 3312;
 		return IIO_VAL_INT;
 	default:
 		return -EINVAL;