[U-Boot-Custodians] SPL / TPL

[Masahiro Yamada]

On Fri, Oct 11, 2019 at 4:08 AM Tom Rini <trini at konsulko.com> wrote:
>
> 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.


You can check that by building every board with CONFIG_TPL=y,
and comparing the sizes between SPL and TPL.



For example, I built  evb-rk3229_defconfig, and got this:

$ arm-linux-gnueabihf-size   spl/u-boot-spl
   text    data     bss     dec     hex filename
  32818    1836      20   34674    8772 spl/u-boot-spl
$ arm-linux-gnueabihf-size   tpl/u-boot-tpl
   text    data     bss     dec     hex filename
  19558    2516      76   22150    5686 tpl/u-boot-tpl


TPL is smaller than SPL, so the rockchip platforms work
in the boot order of TPL -> SPL -> U-Boot


As for rockchip cases, TPL is smaller than SPL, but
is not as small as 4KB.

Was the 3-stage bootstrap needed
in the first place?





> 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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-- 
Best Regards
Masahiro Yamada