Hello,
I want to apply an overlay to a device tree that is compiled without -@
because that's how dtbs are shipped by the Debian kernel package.
I'm using dtc 1.6.1-1 as provided by Debian.
The machine dtb is bcm2836-rpi-2-b.dtb[1]. The source for the dtbo looks
as follows:
uwe@taurus:~/tmp$ cat dht11-overlay.dts
/*
* Overlay for the DHT11/21/22 humidity/temperature sensor modules.
*/
/dts-v1/;
/plugin/;
/ {
compatible = "brcm,bcm2708";
fragment@0 {
target-path = "/";
__overlay__ {
dht11: dht11@0 {
compatible = "dht11";
pinctrl-names = "default";
pinctrl-0 = <&dht11_pins>;
gpios = <&gpio 4 0>;
status = "okay";
};
};
};
fragment@1 {
target-path = "/soc/";
__overlay__ {
gpio: gpio@7e200000 {
dht11_pins: dht11_pins {
brcm,pins = <4>;
brcm,function = <0>; // in
brcm,pull = <0>; // off
};
};
};
};
__overrides__ {
gpiopin = <&dht11_pins>,"brcm,pins:0",
<&dht11>,"gpios:4";
};
};
which is more or less the overlay with the same name provided by the
RaspberryPi Foundation[2].
I can compile and apply the overlay just fine (well there are warnings,
but ...):
uwe@taurus:~/tmp$ dtc -I dts -O dtb dht11-overlay.dts > dht11-overlay.dtbo
dht11-overlay.dts:14.19-20.6: Warning (unit_address_vs_reg): /fragment@0/__overlay__/dht11@0: node has a unit name, but no reg or ranges property
dht11-overlay.dts:27.24-33.6: Warning (unit_address_vs_reg): /fragment@1/__overlay__/gpio@7e200000: node has a unit name, but no reg or ranges property
dht11-overlay.dts:14.19-20.6: Warning (gpios_property): /fragment@0/__overlay__/dht11@0: Missing property '#gpio-cells' in node /fragment@1/__overlay__/gpio@7e200000 or bad phandle (referred from gpios[0])
uwe@taurus:~/tmp$ fdtoverlay -i bcm2836-rpi-2-b.dtb -o bcm2836-rpi-2-b+dht11.dtb dht11-overlay.dtbo
However there is a problem: The original bcm2836-rpi-2-b.dtb has:
uwe@taurus:~/tmp$ fdtdump bcm2836-rpi-2-b.dtb
...
gpio@7e200000 {
....
phandle = <0x00000006>;
....
hdmi@7e902000 {
...
hpd-gpios = <0x00000006 0x0000002e 0x00000001>;
...
the patched dtb has:
...
dht11@0 {
phandle = <0x0000001d>;
status = "okay";
gpios = <0x0000001c 0x00000004 0x00000000>;
pinctrl-0 = <0x0000001b>;
pinctrl-names = "default";
compatible = "dht11";
};
...
gpio@7e200000 {
phandle = <0x0000001c>;
....
hdmi@7e902000 {
...
hpd-gpios = <0x00000006 0x0000002e 0x00000001>;
...
So the gpios property of the dht11 node points to the gpio node as
expected, however the hpd-gpios property of the hdmi node is broken
because the phandle of gpio@7e200000 changed.
I think it should be possible to not overwrite the phandle of
gpio@7e200000 and just reuse the value 6.
Is this a bug, or did I miss a feature that allows me to create a dtbo
that does the right thing?
@Corsac: Maybe it's worth to test if the rpi firmware does a better job
at applying the dtbo? If you test this, please report here.
Best regards
Uwe
[1] https://www.kleine-koenig.org/tmp/bcm2836-rpi-2-b.dtb
[2] https://raw.githubusercontent.com/raspberrypi/linux/5cc390759ed0461bd35744e817470869e99e0484/arch/arm/boot/dts/overlays/dht11-overlay.dts
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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