Re: [PATCH 0/3] Synchronize DTC to 1.7.2

[Tom Rini <trini@konsulko.com>]

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On Thu, Nov 13, 2025 at 01:21:07PM +0100, Marek Vasut wrote:

> Synchronize local copy of DTC with Linux 6.17 , using commits picked
> from Linux kernel. This also includes two fix up patches to make the
> DM core work with new 8-byte alignment checking in libfdt and another
> fix for NULL pointer check that is missing in libfdt.
> 
> This depends on the following patches sent separately, which fix
> various 8-byte alignment problems in the code base:
> 
>  - boot: android: Always use 8-byte aligned DT with libfdt
>  - test/py: android: Point fdt command to aligned addresses
>  - test/py: Use aligned address for overlays in 'extension' test
>  - sandbox: Fix DT compiler address warnings in sandbox DTs
>  - sandbox: Fix DT compiler pin warnings in sandbox DTs
>  - boot: Assure FDT is always at 8-byte aligned address
>  - arm: qemu: Eliminate fdt_high and initrd_high misuse
>  - efi_loader: Assure fitImage from capsule is used from 8-byte aligned address
>  - MIPS: Assure end of U-Boot is at 8-byte aligned offset

So, taking a look at the test branch you pointed me at, my big concern
is size growth. On imx8mp_dhcom_drc02 (where we're already LTO'ing),
with the CI gcc-14.2.0 toolchain full U-Boot grows by more than 6KiB and
SPL by a bit more than 2KiB. This is a bit of a worst-case, imx8mp_navqp
is a bit more than 3KiB / 548 bytes, with the average feeling like
~4KiB/1KiB for aarch64.

I know there are some configuration choices to make libfdt be more
risk-adverse and perform less sanity checks, but I also think we had
fully enabled them.

Frustratingly I think this is why we ended up with:
commit 088bbc1efa8c1efe8e2714b9640055ce984aec93
Author: Patrice Chotard <patrice.chotard@foss.st.com>
Date:   Fri Mar 28 17:31:15 2025 +0100

    dtc: introduce label relative path references
    
    Since introduction of OF_UPSTREAM flag, U-Boot's dtc must be able
    to compile Kernel's device tree.
    
    Since kernel commit 7de129f5389b ("ARM: dts: stm32: stm32mp151a-prtt1l:
    Fix QSPI configuration"), label relative path references has been
    introduced. These label relative path references is not supported
    by current U-Boot dtc version 1.5.0: (see mailing list discussion [1]).
    
    In order to support such label relative patch references
    adds following commit from upstream DTC tree:
    
    commit 651410e54cb9 ("util: introduce xstrndup helper")
    commit ec7986e682cf ("dtc: introduce label relative path references")
    
    [1] https://lore.kernel.org/all/20250115144428.GZ3476@bill-the-cat/T/
    
    Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
    Cc: Tom Rini <trini@konsulko.com>
    Cc: Simon Glass <sjg@chromium.org>
    Reviewed-by: Tom Rini <trini@konsulko.com>
    Reviewed-by: Simon Glass <sjg@chromium.org>

Rather than a full-resync for the last time we needed a feature found
upstream.

There are things we *need* like to be 8-byte aligned and also the
phandle resolution thing I believe inspired your investigations here,
but I don't know if we can take the whole sync. Or maybe needing to work
with upstream to shrink down some parts, I'm unsure.

-- 
Tom

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