[U-Boot] Making U-Boot smaller

[Jagan Teki]

On Tue, May 21, 2019 at 10:14 PM Simon Glass <sjg at chromium.org> wrote:
>
> Hi,
>
> (moved from thread "U-Boot PXA support")
>
> We have of-platdata, which produces C data from the DT, for linking
> into U-Boot. It saves libfdt and DT space. But we still have the DM
> overhead.
>
> We have binman which can insert values into the binary after
> link-time. This is barely used at present, only for accessing the
> location of things in flash.
>
> Another thing is that every little tweak and feature adds a few bytes
> and there are dozens of them in each release. It would be interesting
> to build a board from 10 years ago (like PXA) and see where the growth
> is. My bet is that we could add Kconfig options to disable extra
> features (and enhancements of features) and make quite a difference.
>
> For DM, I think it would be interesting to revisit and compare against
> the initial release, and see if some features could be made optional
> in SPL.
>
> Finally I feel we could implement a single-device API for where
> CONFIG_SPL_DM is not set. We could use the debug UART for serial, a
> single instance of tiny MMC for MMC, etc.

This is what I'm looking for quite sometime, a tiny MMC which would
bypass the mmc stack and do the possible stuff in SPL, since we don't
have any option to use full DM in SPL (specifically for Allwinner 64
SoC's). API that would atleast compatible with DM with small
foot-print would help.