Re: [PATCH] ARM: dts: omap3-n900: correct the accelerometer orientation

On Mon, 29 Jul 2024 22:40:22 +0200
Sicelo [off-list ref] wrote:

Hello Andreas

On Sun, Jul 28, 2024 at 10:06:58AM +0200, Andreas Kemnade wrote:

quoted

quoted

On Mon, Jul 22, 2024 at 01:31:11PM +0200, Sicelo A. Mhlongo
wrote:  

quoted

Negate the values reported for the accelerometer z-axis in
order to match
Documentation/devicetree/bindings/iio/mount-matrix.txt.

Fixes: 14a213dcb004 ("ARM: dts: n900: use iio driver for
accelerometer")

Signed-off-by: Sicelo A. Mhlongo <redacted>
---
 arch/arm/boot/dts/ti/omap/omap3-n900.dts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/ti/omap/omap3-n900.dts

b/arch/arm/boot/dts/ti/omap/omap3-n900.dts index
07c5b963af78..4bde3342bb95 100644 ---
a/arch/arm/boot/dts/ti/omap/omap3-n900.dts +++
b/arch/arm/boot/dts/ti/omap/omap3-n900.dts @@ -781,7 +781,7 @@
accelerometer@1d { 
 		mount-matrix =	 "-1",  "0",  "0",
 				  "0",  "1",  "0",
-				  "0",  "0",  "1";
+				  "0",  "0",  "-1";
 	};
 
 	cam1: camera@3e {
-- 
2.45.2
    

CC: Aaro Koskinen <aaro.koskinen@iki.fi>, Andreas Kemnade
[off-list ref]
  

I would expect it to be a rotation matrix but it is not. So maybe
this should be fixed in,the driver?  

The mount matrix is documented in the kernel docs [1], and this patch
implements the suggestion that the z-axis should "be negative under
the screen and positive in front of it, toward the face of the user."

On the N900, the accelerometer is mounted such that the raw z-values
are opposite to the specification in the kernel docs. The driver
itself seems to be correct, and is used on a number of other boards
(such as Motorola Droid 4), reporting expected values when used in
conjuction with mount matrices.

Ok, I did not notice the other -1. It was mirroring before and now it
is a clear 180 deg turn on the y-axis.

So
Reviewed-By: Andreas Kemnade <andreas@kemnade.info>