[U-Boot-Custodians] SPL / TPL

[Tom Rini]

On Fri, Oct 11, 2019 at 12:26:10PM +0900, Masahiro Yamada wrote:
> On Fri, Oct 11, 2019 at 12:17 PM Tom Rini <trini at konsulko.com> wrote:
> >
> > On Fri, Oct 11, 2019 at 12:10:53PM +0900, Masahiro Yamada wrote:
> > > 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?
> >
> > I believe the answer is yes, Rockchip (and a few other aarch64
> > platforms) have small and non-power-of-2 initial memory constraints.
> 
> Why is "non-power-of-2" constraint relevant to this topic?

You mentioned 4k, which is a natural feeling constraint.  I'm just
noting that some of the platforms here end up with limits that aren't a
nice round number.

-- 
Tom
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