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

[Jean-Jacques Hiblot]

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.

JJ


> This series looks better.
> Is this able to also handle different images then just dtbs?
> Thanks,
> Michal
>