[U-Boot-Custodians] SPL / TPL

[Tom Rini]

On Thu, Oct 10, 2019 at 09:46:38AM +0200, Marek Vasut wrote:
> On 10/10/19 9:40 AM, Wolfgang Denk wrote:
> > Dear Masahiro,
> > 
> > In message <CAK7LNAR45-6SEAeGyjT8o5jP=6iNcSP=A4pW2rQV9V_JfGTi0w at mail.gmail.com> you wrote:
> >>
> >> This discussion started from this patch:
> >> https://patchwork.ozlabs.org/patch/662396/
> >>
> >> It happened before the rockchip stuff.
> > 
> > Yes, thanks for the link. Apparently I missed that discussion then :-(
> > 
> > I still cannot see where this thinking that "SPL is big and has all
> > features" and "TPL is small" is coming from.  If someone has
> > implemented it in this way, then he did a major mistake.
> 
> Note that back in the old OneNAND days, TPL was used as the 1 kiB tiny
> loader and that loaded the SPL. Even today, there are less features
> available for TPL than for SPL, although they are constantly being added
> to make these two things virtually identical. So I have a feeling that
> this situation naturally evolved that TPL is smaller than SPL and goes
> before SPL.
> 
> Just out of curiosity, how many platforms are there that do
> SPL->TPL->U-Boot and how many do TPL->SPL->U-Boot ?

This last point here is what I'm also wondering about.  My gut is that
README.TPL is more "old aspiration" than "what we have implemented".
And, setting aside some of the back-and-forth jumps we can have, the
flow is:
ROM/etc -> Tiny Program Loader -> SPL -> U-Boot or Linux

and CONFIG_TPL_xxx is used to control the building, or not building, of
various portions.

-- 
Tom
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