[U-Boot] [PATCH] spl: dm: Make it possible for the SPL to pick its own DTB from a FIT

[Tom Rini <trini@konsulko.com>]

On Fri, Jul 07, 2017 at 01:44:39PM +0200, Jean-Jacques Hiblot wrote:

> u-boot can be embedded within a FIT image with multiple DTBs. It then
> selects at run-time  which one is best suited for the platform.
> Use the same principle here for the SPL: put the DTBs in a FIT image,
> compress it (LZO, GZIP, or no compression) and append it at the end of the
> SPL.
> 
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> ---
> 
> The impact in terms of boot time is not high when using LZO but I gues it can vary
> from platform to platform.
> The size of the SPL binary is increased (1.5kB more code on ARM), but the compression
> really flattens the DTBS. so at the end of the day, enabling this option doesn't add much.
> 
> Here are some sumbers with a DRA7 platform (numbers in bytes):
>                           size  delta with ref
>   MLO.reference         123450
>   MLO.lzo_1_DTB         123715    +265
>   MLO.lzo_4_DTB         124237    +787
>   MLO.gzip_4_DTB        132006    +8556
>   MLO.no_comp_4_DTB     134184    +10734

Bearing in mind that you said in a follow up this is RFC, I'm ignoring
all of the stuff that I believe you would fix in a v1.  At the heart of
it, are you able to tell different boards before you have a DTB loaded?
I keep coming back to the problem that for SPL it seems like we should
be able to do what Franklin did for keystone
(https://patchwork.ozlabs.org/patch/777242/) and have a 'fake' dts file
that represents the SoC such that any real boards can get U-Boot loaded
and from there have the real board dtb be used.  Or am I forgetting
something?  Thanks!

-- 
Tom
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