On Thu, Feb 4, 2021 at 10:44 PM Hector Martin 'marcan' [off-list ref] wrote:

On 05/02/2021 06.29, Arnd Bergmann wrote:

quoted

On Thu, Feb 4, 2021 at 9:39 PM Hector Martin [off-list ref] wrote:

We tend to split the dts file into one file per SoC and one for the
specific board. I guess in this case the split can be slightly different,
but it does feel better to be prepared for sharing a lot of the contents
between the different products.

In most cases, you'd want the 'aliases' and 'chosen' nodes to be
in the board specific file.

I thought about that, but wasn't sure if splitting it up at this early
stage made much sense since I'm not sure what the split should be, given
all supported hardware is the same for all 3 released devices.

I'm happy to throw the aliases/chosen nodes into board specific files if
you think that's a good starting point. Perhaps /memory too? Those
properties are filled in/patched by the bootloader anyway...

Yes, I think that would help make it more consistent with other
platforms even if we don't care too much here.

There are also DT overlays; I was wondering if we could use those to
keep the hierarchy and avoid having many duplicate trees in a
hypothetical bootloader that embeds support for a large set of hardware,
having it construct the final devicetree on the fly from SoC + a board
overlay (and possibly further levels); but I'm not sure how that ties in
with the device trees that live in the Linux tree. Do you have any
pointers about this?

We don't really have overlays in the kernel sources (yet), though it
is something that keeps coming up. For the moment, I'd just
assume you can have one .dts file for each thing you want to
support and keep the shared bits in .dtsi files.

quoted

Did you see the discussion on the #armlinux channel about the possibility
of moving the cpu-enable method to PSCI based on a UEFI runtime
interface?

...

I saw it go by but need to review it again; I've been missing too much
sleep this week :) thanks for the reminder.

I think we might want to start with spin-table for now, given that there
are no kernel changes needed anyway, but I'm happy to take the protoype
for a spin (:)) and try implementing it in m1n1.

I do think it's valuable for whatever we do, at this stage, to not
require u-boot; having that be an integral part of the boot chain is
perfectly fine in the future but right now it helps to have a simple
boot chain while we work out the early bring-up, and while u-boot grows
the required support.

Agreed.

       Arnd

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