[fedora-arm] Re: uboot dtb overlays: clarification needed

On Fri, Aug 17, 2018 at 5:58 PM, Alessio Ciregia <alciregi@gmail.com> wrote:
> Hello.
> I'm doing a lot of tests with Fedora 28 (armv7hl) and I would like
> some clarifications. I looked around for some info, but I'm unable to
> get specific responses to my questios.
>
> - The loaded dtb (on a Raspberry Pi 3) is bcm2837-rpi-3-b.dtb: who
> tell the system to load such dtb?

U-Boot currently tells it to load.

> - Does the /boot/uEnv.txt file is taken into account in Fedora?

Not really

> - Does the dtoverlay option (n config.txt) is taken into account by Fedora?

Not currently but I'm working to have that work for Fedora 29.
Basically at the moment it uses a kernel provided DT which is loaded
and passed to the kernel by U-Boot. My plan for F-29 (I was hoping it
would actually be in F-28 but there was issues and I don't have the
time to finish it) is to use the firmware to load a "upstream kernel"
DT which then uses the dtoverlay configurations bits in config.txt
which the RPi firmware mashes them all together as a single DT and
passes it to U-Boot which in turn passes it onto the kernel enabling
us to use support HATs.

I believe all the bits are now in place (firmware, U-Boot etc) and I
just need to apply some config and test to make sure it all works, and
falls back to the current way if there's not bits specified.

Peter
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