[U-Boot] [RFC PATCH v2 00/12] Add support for applications of overlays in SPL

[Simon Glass]

Hi Jean-Jacques,

On Wed, 17 Apr 2019 at 02:48, Jean-Jacques Hiblot <jjhiblot at ti.com> wrote:
>
> Tom, Simon,
>
> On 28/03/2019 15:03, Michal Simek wrote:
> > On 27. 03. 19 16:38, Jean-Jacques Hiblot wrote:
> >> The purpose of this series is to provide the SPL with ability to apply
> >> overlays for u-boot. this is only a RFC so far, to get a feedback on the
> >> approach.
> >>
> >> Our use-case is the support of the daughter boards of the AM65x EVM. In
> >> Linux, each board is supported by a unique overlay. The presence of the
> >> boards is detected at runtime, and some useful features (like USB) are
> >> implemented on those daughter boards. Instead of providing multiple dtbs
> >> and fall in a combinatorial pit, we propose to use DT overlays.
> >>
> >> Patch #1 "spl: fit: Add support for applying DT overlay" has been posted
> >> a few weeks ago by Michal Simek.
> >> Patch #2 and #3 amend Michal's patch.
> >> Patch #4 and #5 are simple fixes for the Makefile
> >> Patch #6 is not required but relates to this series and will be required
> >> later by the AM6x platform
> >> Patch #7 may be a bit controversial. It basically replaces u-boot.img with
> >> a symlink to u-boot.itb in case we use a "complex" FIT (ie: if
> >> SPL_FIT_SOURCE or SPL_FIT_GENERATOR are set). This breaks buildman for
> >> several platforms because not all the binaries embedded in the FIT are
> >> available.
> >> Patch #9 adds a way to dynamically select the DT overlays. That is were we
> >> would use HW detection to select the required overlays. In that case, the
> >> board-level code tells what overlay it needs (it gives the name of the
> >> node).
> >> Patch #10 disables advanced SPL FIT features to keep the size of the SPL of
> >> the am335x_evm in check
> >> Patch #11 is not required, but demonstrates on a DRA76-evm how this series
> >> can be used.
> >>
> >> On arm, if overlay are supported, this series increases the size of the SPL
> >> by 3-4 kB.
> >>
> >> Changes in v2:
> >> - reworked board_fit_get_additionnal_images() and how it used in spl_fit.c
> >> - removed dtbo generation from dtso files and use .dts extension for the
> >>    overlays
> >> - add dynamic allocation usage in a separate patch
> >> - defconfig change for the am335x_evm
>
> I don't know if you had time to look at this series. Its purpose is to
> allow the SPL to apply DT overlays to the FDT loaded for u-boot based on
> a runtime detection of the HW.
>
> We are going to need this kind of feature in our tree, I would really
> appreciate your feedback. I don't want to go in the wrong direction.

No I have not looked at this yet. My only comment so far is to make
sure that this feature is fully optional so it does not expand the
size of SPL for other boards.

Regards,
Simon