| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <q2am2ffsvb5ajyzmns3gr5xns43mlpkfbj2ohvltml6tedhzre@d2h2jvp73ctv>
Date: Sun, 21 Sep 2025 15:23:08 +0200
From: Ondřej Jirman <megi@....cz>
To: guptarud@...il.com, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
Heiko Stuebner <heiko@...ech.de>, devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/5] arm64: dts: rk3399-pinephone-pro: Add
accelerometer sensor support
On Sun, Sep 21, 2025 at 03:10:50PM +0200, megi xff wrote:
> Hi,
>
> On Sun, Sep 21, 2025 at 01:04:20AM -0700, Rudraksha Gupta via B4 Relay wrote:
> > From: Ondrej Jirman <megi@....cz>
> >
> > Pinephone Pro uses mpu6500.
> >
> > Signed-off-by: Ondrej Jirman <megi@....cz>
> > Signed-off-by: Rudraksha Gupta <guptarud@...il.com>
> > ---
> > arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts b/arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts
> > index 65ee0b805034a4357a766d4f1f9efa2d4a843d77..21ff12ac5f6e52041f485c9f2702f5a15ee831f9 100644
> > --- a/arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts
> > +++ b/arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts
> > @@ -544,7 +544,13 @@ mpu6500@68 {
> > reg = <0x68>;
> > interrupt-parent = <&gpio1>;
> > interrupts = <RK_PC6 IRQ_TYPE_LEVEL_LOW>;
> > + vdd-supply = <&vcc_1v8>;
> > vddio-supply = <&vcc_1v8>;
> > +
> > + mount-matrix =
> > + "1", "0", "0",
> > + "0", "-1", "0",
> > + "0", "0", "1";
>
> I'm not sure where you got this patch, but it's not from me (I know for sure
> I never did any mount-matrix testing/DT patches) and should not have my
> Signed-of-by.
Oh well, this is about the accelerometer. :) Anyway, this review should still be
useful for the other patch in your series adding magnetometer support. You
should add mount-matrix to that, too, since it's not an identity matrix
apparently, which is the default without specifying mount-matrix in DT.
Regards,
o.
> I have this in my tree https://codeberg.org/megi/linux/commit/d7cd2eab931e32fa94408a96d73b4e6c0616107a
> Which is:
>
> Signed-of-by: Leonardo G. Trombetta <lgtrombetta@....com>
>
> And has different values on top of that and much more explanation. :)
>
> mount-matrix =
> "0", "1", "0",
> "-1", "0", "0",
> "0", "0", "1";
>
> So I guess you'd need to provide a bit more information about how you
> tested/verified these values, or where you've got them from.
>
> See: https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/iio/mount-matrix.txt#L93
>
> Looking at where the magnetometer is mounted, it's mounted on the bottom side of
> the PCB (U29 chip):
>
> https://xff.cz/dl/tmp/a0a36024d1ce9b15.png
> https://xff.cz/dl/tmp/8f9dce63f3a7f3f4.png
>
> Which means it would face from the PCB in the direction of the display and up
> towards the user who is looking at the display, due to the way PCB is mounted.
>
> From the datasheet: https://xff.cz/dl/tmp/6b163fbe4335e58e.png the relationship
> of the chip orientation to measured XYZ values.
>
> Putting it together https://xff.cz/dl/tmp/a17eec1488ea7705.png
>
>
> - Z increases downwards away from user looking at the phone display
> - Y increases to the left
> - X increases to the bottom of the display (towards USB-C connector)
>
>
> DT bindings state:
>
> - Magnetometers (compasses) have their world frame of reference relative to the
> geomagnetic field. The system orientation vis-a-vis the world is defined with
> respect to the local earth geomagnetic reference frame where (y) is in the
> ground plane and positive towards magnetic North, (x) is in the ground plane,
> perpendicular to the North axis and positive towards the East and (z) is
> perpendicular to the ground plane and positive upwards.
>
> ^^^ North: y > 0
>
> (---------)
> ! !
> ! !
> ! !
> ! ! >
> ! ! > North: x > 0
> ! 1 2 3 ! >
> ! 4 5 6 !
> ! 7 8 9 !
> ! * 0 # !
> (---------)
>
> Mount matrix in your patch just flips Y axis and leaves the rest as is, so that
> doesn't seem to match what bindings ask for at all.
>
> Just based on the PCB component placement and datasheets we should have:
> (small letters = DT bindings, big letters output from magnetometer)
>
> x = -Y
> y = -X
> z = -Z
>
> So that gives:
>
> mount-matrix =
> "0", "-1", "0",
> "-1", "0", "0",
> "0", "0", "-1";
>
> I did a quick test (rotating the phone on the table with display
> facing up):
>
> - Y is highest when right edge of the phone faces north:
>
> in_magn_x_raw: -3074
> in_magn_y_raw: -690
> in_magn_z_raw: -1622
>
> and lowest when pointing south
>
> in_magn_x_raw: -3569
> in_magn_y_raw: -2052
> in_magn_z_raw: -1824
>
> (X is roughly the same)
>
> so that matches x = Y
>
>
> - X is highest when top edge of the phone faces north:
>
> in_magn_x_raw: -3990
> in_magn_y_raw: -1287
> in_magn_z_raw: -1677
>
> and lowest when facing south
>
> in_magn_x_raw: -2553
> in_magn_y_raw: -1314
> in_magn_z_raw: -1624
>
> (Y is roughly the same)
>
> y = X
>
> - Z is lower when display faces up
>
> in_magn_x_raw: -4083
> in_magn_y_raw: -1179
> in_magn_z_raw: -2436
>
> and higher with display facing down
>
> in_magn_x_raw: -3999
> in_magn_y_raw: -1584
> in_magn_z_raw: 393
>
> z = -Z
>
> So based on that mount-matrix should be:
>
> mount-matrix =
> "0", "1", "0",
> "1", "0", "0",
> "0", "0", "-1";
>
> Go figure. :-D
>
> Best regards,
> o.
>
>
> > };
> > };
> >
> >
> > --
> > 2.51.0
> >
> >
Powered by blists - more mailing lists