Need help with FDT overlay

[Simon Glass]

Hi Matwey,

On Sat, 21 Mar 2026 at 11:20, Matwey V. Kornilov
<matwey.kornilov at gmail.com> wrote:
>
> I compile dtbo as the following;
>
> cpp -x assembler-with-cpp -I /home/matwey/lab/linux/include
> overlay.dtso overlay.i
> dtc -@ -O dtb -o overlay.dtbo overlay.i
>
> Decompiled overlay.dtbo looks like this:
>
> /dts-v1/;
>
> / {
>
>     fragment at 0 {
>         target = <0xffffffff>;
>
>         __overlay__ {
>             status = "okay";
>         };
>     };
>
>     fragment at 1 {
>         target = <0xffffffff>;
>
>         __overlay__ {
>             status = "okay";
>         };
>     };
>
>     fragment at 2 {
>         target-path = "/";
>
>         __overlay__ {
>
>             i2c-gpio {
>                 compatible = "i2c-gpio";
>                 sda-gpios = <0xffffffff 0x08 0x00 0x06>;
>                 scl-gpios = <0xffffffff 0x08 0x0f 0x06>;
>                 i2c-gpio,delay-us = <0x02>;
>                 #address-cells = <0x01>;
>                 #size-cells = <0x00>;
>                 status = "okay";
>                 phandle = <0x01>;
>             };
>         };
>     };
>
>     __symbols__ {
>         i2c_gpio = "/fragment at 2/__overlay__/i2c-gpio";
>     };
>
>     __fixups__ {
>         i2c0 = "/fragment at 0:target:0";
>         i2c1 = "/fragment at 1:target:0";
>         pio = "/fragment at 2/__overlay__/i2c-gpio:sda-gpios:0",
> "/fragment at 2/__overlay__/i2c-gpio:scl-gpios:0";
>     };
> };
>
>
> I am not sure about the size. How do I check it correctly? Now, I just do
>
> fdt resize 16384
>
> сб, 21 мар. 2026 г. в 18:02, Simon Glass <sjg at chromium.org>:
> >
> > Hi Matwey,
> >
> > On Sat, 21 Mar 2026 at 06:55, Matwey V. Kornilov
> > <matwey.kornilov at gmail.com> wrote:
> > >
> > > Hello,
> > >
> > > I am running U-boot 2026.01 with orangepi_zero2w config and I am
> > > trying to apply my hand-written dtbo via fdt apply.
> > > The issue is that the fdi apply command just hangs forever for me. The
> > > issue only appears when I try to append a new node to the root. How
> > > could I find what is going wrong here?
> > >
> > > The overlay source is the following:
> > >
> > > /dts-v1/;
> > > /plugin/;
> > >
> > > #include <dt-bindings/i2c/i2c.h>
> > > #include <dt-bindings/gpio/gpio.h>
> > >
> > >
> > > &i2c0 {
> > >     status = "okay";
> > > };
> > >
> > > &i2c1 {
> > >     status = "okay";
> > > };
> > >
> > > &{/} {
> > >     i2c_gpio: i2c-gpio {
> > >         compatible = "i2c-gpio";
> > >         sda-gpios = <&pio 8 0 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>; // PI0  (29)
> > >         scl-gpios = <&pio 8 15 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>; // PI15 (31)
> > >         i2c-gpio,delay-us = <2>;        /* ~100 kHz */
> > >         #address-cells = <1>;
> > >         #size-cells = <0>;
> > >         status = "okay";
> > >     };
> > > };
> > >
> >
> > Can you provide thte dtc command you are using to build this? Is there
> > enough spare space in the dtb? I'm not sure what would cause it to
> > hang.
> >
> > Regards,
> > Simon

It might help to have the console log too. I can't see any way this
can hang unless the addreses are wrong and something important is
overwritten.

Try this to see the address:

fdt header

Compare to 'meminfo' so you can tell that there is nothing important
above the fdt. Also where do you load the overlay?

BTW U-Boot uses hex, so it should be 'fdt resize 4000'

Regards,
Simon