u-boot DT configuration node

From: Michal Simek <michal.simek@xilinx.com>
To: Rob Herring <robh@kernel.org>
Cc: "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"u-boot@lists.denx.de" <u-boot@lists.denx.de>,
	Tom Rini <trini@konsulko.com>,
	Loic Poulain <loic.poulain@linaro.org>
Subject: u-boot DT configuration node
Date: Wed, 1 Apr 2020 11:23:13 +0200	[thread overview]
Message-ID: <6cdf20c3-7b74-679c-0e6f-4d385d12f9fe@xilinx.com> (raw)

Hi Rob and others,

for couple of years already u-boot is using config node in root DT for
u-boot configuration.

Here is one example in u-boot source code.
https://gitlab.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/exynos5250-spring.dts#L47

And here is dt binding description
https://gitlab.denx.de/u-boot/u-boot/-/blob/master/doc/device-tree-bindings/config.txt

I was checking dt binding specification and there no such a thing
described there. It means I expect this is more adhoc u-boot solution.
We have reached the point where could be beneficial to put some u-boot
specific configurations to DT.

Actually I have done similar thing some time ago too by using chosen
node and add xilinx specific property there to point to eeprom.
https://gitlab.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/zynqmp-zcu102-revA.dts#L39

I think it is a time to discuss it and do it properly.

First of all my question is where we could list SW prefixes to make sure
that they are listed and everybody is aware about it. We have
vendor-prefixes and we should have a way to record also prefixes for sw
projects. U-Boot is using u-boot. Xen has file in the kernel with using
xen prefix. At least these two should be listed.

Next my question is what is the recommended way to pass sw specific
parameters via DT? I think using chosen node is more appropriate then
adhoc config node. Or is there a better way how this should be done?

Thanks,
Michal