linux-kernel - Re: [PATCH v2 0/3] arm64: dts: rockchip: minimal support for Pre-ICT tester adapter for RK3588 Jaguar + add overlay tests

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Message-ID: <3324197.aV6nBDHxoP@diego>
Date: Thu, 23 Jan 2025 15:13:01 +0100
From: Heiko Stübner <heiko@...ech.de>
To: Quentin Schulz <quentin.schulz@...rry.de>,
 Niklas Cassel <cassel@...nel.org>
Cc: Quentin Schulz <foss+kernel@...il.net>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 Jagan Teki <jagan@...eble.ai>,
 Michael Riesch <michael.riesch@...fvision.net>, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject:
 Re: [PATCH v2 0/3] arm64: dts: rockchip: minimal support for Pre-ICT tester
 adapter for RK3588 Jaguar + add overlay tests

Am Mittwoch, 22. Januar 2025, 17:12:26 CET schrieb Niklas Cassel:
> On Wed, Jan 22, 2025 at 04:38:16PM +0100, Quentin Schulz wrote:
> > So essentially, if SPL_ATF_NO_PLATFORM_PARAM is selected (the default for
> > RK356x, RK3588, forced on on RK3308, enabled for the majority of RK3399
> > boards, enabled for all RK3328 boards) the DT won't be passed to TF-A so no
> > issue in terms of size on that side.
> > If it is not selected, for TF-A < 2.4 (released 20201117, 4 years ago), a
> > DTB bigger than 64KiB will crash TF-A.
> > If it is not selected, for TF-A >= 2.4, a DTB bigger than 128KiB will result
> > in TF-A not being able to read the DTB (for Rockchip, that means not being
> > able to derive the UART settings (controller and baudrate) to use, and will
> > use the compile-time default instead).
> 
> Not everyone is using binary blobs from Rockchip.
> On my rock5b (rk3588), I'm building the bootloader using buildroot,
> which is using upstream TrustedFirmware-A (v2.12).
> 
> 
> > In short, I don't know where to go with that additional piece of
> > information, but this is a bit bigger than simply moving things around and
> > adding compile-time tests for overlay application.
> 
> This is significant information indeed.

I guess the question is, can this hurt existing devices?

As Quentin mentioned, this only affects DTs that get handed over from
U-Boot to TF-A (and maybe OP-TEE).

So the whole range of things loading their DT from extlinux.conf or
whatever are not really affected.


DTs U-Boot can hand over are 2 types,
(1) built from within u-boot and
(2) stored somewhere centrally (SPI flash).


Case (1) is again not affected, as U-Boot (and other bootloaders) may
very well sync the DTS files, but generally not the build-system, so if
U-Boot (or any other bootloader) creates DTBs with symbols is completely
their own choice.


And for case (2) I see the manufacturer being responsible. Having the DT
in central storage makes it somewhat part of a "bios"-level in the hirarchy
and the general guarantee is that new software _will work_ with older DTs,
but the other way around is more a nice to have (old SW with new DTB).

So if some manufacturer has a centrally located DTB this does not matter
until they upgrade, and when that happens I do expect testing to happen
at the manufacturers side, before rolling out a "bios update"


Heiko