Re: [PATCH] arm: init: add an option to use FDT from previous bootloader

[Tom Rini <trini@konsulko.com>]

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On Tue, Oct 24, 2023 at 08:52:22PM +0100, Caleb Connolly wrote:
> 
> 
> On 24/10/2023 20:25, Tom Rini wrote:
> > On Tue, Oct 24, 2023 at 12:32:35PM +0100, Caleb Connolly wrote:
> > 
> >> Add a new config option to allow u-boot to reuse the FDT provided by the
> >> previous stage bootloader when available.
> >>
> >> On some boards the previous stage bootloader can populate
> >> platform-specific parts of the devicetree such as the memory node, this
> >> allows us to avoid hardcoding it in u-boot and instead determine it
> >> dynamically at runtime.
> >>
> >> Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
> >> ---
> >> This patch will improve generic support for Qualcomm boards by enabling
> >> us to configure the memory map at runtime rather than having hardcoded
> >> maps on a per-device basis. I've gone for this approach initially to try
> >> and avoid introducing board specific code where possible, but I'm happy
> >> to rework this into mach-snapdragon if that's preferred.
> >> ---
> >> base-commit: e65b5d35c9116485366bb08138043d51220551da
> >>
> >> // Caleb (they/them)
> >> ---
> >>  arch/arm/lib/save_prev_bl_data.c |  7 +++++++
> >>  boot/Kconfig                     | 10 ++++++++++
> >>  include/init.h                   |  9 +++++++++
> >>  lib/fdtdec.c                     |  7 ++++++-
> > 
> > So what is different with this instead of using save_boot_params ? I'm
> > not saying this isn't needed, but I don't immediately see why
> > save_boot_params + (OF_HAS_PRIOR_STAGE=y&&OF_BOARD=y) isn't the solution
> > to the problem.
> 
> OF_BOARD would work here by implementing board_fdt_blob_setup() for
> mach-snapdragon, my hope was to avoid doing this in a board-specific
> way, but if that's preferred then I can totally do that instead.
> 
> I left a comment below the patch about this, although it probably wasn't
> super clear.

Ah, yes.  I guess I don't see what I suggested as "board specific" in
that outside of efforts like bloblist that Simon mentioned, every
semiconductor is slightly different.  So yes please, OF_BOARD and
board_fdt_blob_setup and so forth instead, thanks.

-- 
Tom

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