[U-Boot] What if ATF can be part of U-Boot source, like SPL?

[Tom Rini]

On Sun, Jun 30, 2019 at 04:03:52PM +0200, Marek Vasut wrote:
> On 6/30/19 3:57 PM, Tom Rini wrote:
> > On Sat, Jun 29, 2019 at 08:32:00PM +0530, Jagan Teki wrote:
> > 
> >> In terms of code maintenance and development feasibility it is always
> >> a better approach to have out-of-tree code or binary to be part of
> >> in-house source tree.
> >>
> >> This is what exactly it was done for SPL, if I'm not wrong. So can we
> >> do the same thing for ATF on ARM64 SoCs?
> >>
> >> We are using ATF (on Allwinner) to switch EL3 to EL2 for start loading
> >> U-Boot proper and minimal PSCI, PMIC initialization. So assuming the
> >> functionality of ATF (like here) is limited so the code it require can
> >> be limited too, so why can't this code to be part of U-Boot tree?
> >>
> >> This would ultimately avoid out-off-tree ATF builds with associated
> >> variable exporting during u-boot builds.
> >>
> >> More over this idea would also help to design a single-step bootloader
> >> where it can't depends on out-of-tree sources.
> >>
> >> Code sync from ATF source to U-Boot can be possible in-terms licensing
> >> point-of-view since ATF licensed under BSD-3-Clause.
> >>
> >> I'm thinking this can be a worth-idea to look at it and I'm sure It
> >> may require some hard changes and other things to consider but just
> >> posted to understand how hard or feasible or meaningful it is?
> >>
> >> Feel free for any comments?
> > 
> > Given that we have "TPL" and "SPL", my "pie in the sky" wish would be
> > for the ability to build different U-Boots to fill the different aspects
> > of the aarch64 boot flow.
> > 
> > That said, patches that would in turn allow for users to locally add ATF
> > as a git submodule and then build that, if cleanly done, could be
> > interesting.  But must not impact the normal build flow.
> 
> So can we also add Linux as a submodule ? And glibc ? Maybe busybox too ?

Just as you suggested Jagan look at other SoCs and how they assemble
images, I think you also need to take a wider look around.  The concept
of "take U-Boot, other firmware blobs, combine and mangle that" is
somewhat widely used.  It's not just sunxi that spits out a "can't find
ATF, this image won't boot!" warning.  If we can cleanly and solve that
by easy for users to add git submodules to their tree (I am _not_ saying
mainline U-Boot add submodules, to be clear) and they then get
functional images, that will help a lot of different groups.  We have a
lot of README files today in-tree telling people to jump through hoops
to get ATF and put it somewhere and run another tool on top.

-- 
Tom
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