Hi Tom,
On Tue, 11 Feb 2025 at 14:22, Tom Rini <tr...@konsulko.com> wrote:
>
> On Tue, Feb 11, 2025 at 08:03:20AM -0700, Simon Glass wrote:
> > Hi,
> >
> > I just wanted to send a note to (re-)introduce my ideas[1] for the
> > next iteration of xPL.
> >
> > A recent series introduced 'xPL' as the name for the various
> > pre-U-Boot phases, so now CONFIG_XPL_BUILD means that this is any xPL
> > phase and CONFIG_SPL means this really is the SPL phase, not TPL. We
> > still use filenames and function naming which uses 'spl', but could
> > potentially adjust that.
> >
> > The major remaining problem IMO is that it is quite tricky and
> > expensive (in terms of time) to add a new phase. We also have some
> > medium-sized problems:
> >
> > a. The $(PHASE_), $(SPL_) rules in the Makefile are visually ugly and
> > can be confusing, particularly when combined with ifdef and ifneq
> >
> > b. We have both CONFIG_IS_ENABLED() and IS_ENABLED() and they mean
> > different things. For any given option, some code uses one and some
> > the other, depending on what problems people have met along the way.
> >
> > c. An option like CONFIG_FOO is ambiguous, in that it could mean that
> > the option is enabled in one or more xPL phases, or just in U-Boot
> > proper. The only way to know is to look for $(PHASE_) etc. in the
> > Makefiles and CONFIG_IS_ENABLED() in the code. This is very confusing
> > and has not scaled well.
> >
> > d. We need to retain an important feature: options from different
> > phases can depend on each other. As an example, we might want to
> > enable MMC in SPL by default, if MMC is enabled in U-Boot proper. We
> > may also want to share values between phases, such as TEXT_BASE. We
> > can do this easily today, just by adding Kconfig rules.
>
> I agree with a through c and for d there are likely some cases even if
> I'm not sure TEXT_BASE is a good example. But I'm not sure it's as
> important as the other ones.
OK. No, TEXT_BASE is not a great example in my book either. But it is
true that SPL needs to know U-Boot's text base.
Here's another:
config SPL_SYS_MALLOC_F_LEN
default SYS_MALLOC_F_LEN
config TPL_SYS_MALLOC_F
default y if SPL_SYS_MALLOC_F
config TPL_SYS_MALLOC_F_LEN
depends on TPL_SYS_MALLOC_F
default SPL_SYS_MALLOC_F_LEN
>
> > Proposal
> >
> > 1. Adjust kconf to generate separate autoconf.h files for each phase.
> > These contain the values for each Kconfig option for that phase. For
> > example CONFIG_TEXT_BASE in autoconf_spl.h is SPL's text base.
> >
> > 2. Add a file to resolve the ambiguity in (c) above, listing the
> > Kconfig options which should not be enabled/valid in any xPL build.
> > There are around 200 of these.
> >
> > 3. Introduce CONFIG_PPL as a new prefix, meaning U-Boot proper (only),
> > useful in rare cases. This indicates that the option applies only to
> > U-Boot proper and is not defined in any xPL build. It is analogous to
> > CONFIG_TPL_xxx meaning 'enabled in TPL'. Only a dozen of these are
> > needed at present, basically to allow access to the value for another
> > phase, e.g. SPL wanting to find CONFIG_PPL_TEXT_BASE so that it knows
> > the address to which U-Boot should be loaded.
> >
> > 4. There is no change to the existing defconfig files, or 'make
> > menuconfig', which works just as today, including dependencies between
> > options across all phases.
> >
> > 5. (next) Expand the Kconfig language[2] to support declaring phases
> > (SPL, TPL, etc.) and remove the need for duplicating options (DM_MMC,
> > SPL_DM_MMC, TPL_DM_MMC, VPL_DM_MMC), so allowing an option to be
> > declared once for any/all phases. We can then drop the file in 2
> > above.
> >
> > With this, maintaining Kconfig options, Makefiles and adding a new
> > phase should be considerably easier.
>
> I think this will not make our life easier, it will make things harder.
>
> I think what we've reached now shows that Yamada-san was correct at the
> time in saying that we were going down the wrong path with how we
> handled SPL/TPL.
You've mentioned this quite a few times over the years. Is there a
reference to what he suggested we should do? Or perhaps it is what you
have below.
>
> My request instead is:
> - Largely drop SPL/TPL/VPL (so no DM_MMC and SPL_DM_MMC and so on, just
> DM_MMC) as a prefix.
> - Likely need to introduce a PPL symbol as you suggest.
> - Make PPL/SPL/TPL/VPL be a choice statement when building a defconfig.
Good idea.
> - Split something like rockpro64-rk3399_defconfig in to
> rockpro64-rk3399_ppl_defconfig
> rockpro64-rk3399_spl_defconfig rockpro64-rk3399_tpl_defconfig
> and add Makefile logic such that for X_defconfig as a build target but
> not configs/X_defconfig not existing, we see if any of
> configs/X_{ppl,spl,tpl,vpl}_defconfig exist and we run a builds in
> subdirectories of our object directory, and then using binman combine
> as needed.
This means splitting the existing file into a separate one for each
phase. I believe that will be hard to manage.
> - Maybe instead the Makefile logic above we would parse X_defconfig
> and see if it's a different format of say PHASE:file to make it
> easier to say share a single TPL config with all rk3399, have a few
> common SPL configs and then just a board specific PPL.
>
> This solves (a) by removing them entirely. This solves (b) by removing
> the ambiguity entirely (it will be enabled or not). As a bonus for (b)
> we can switch everyone to IS_ENABLED(CONFIG_FOO) and match up with the
> Linux Kernel again. This solves (c) again by removing it entirely.
The scheme I propose removes a-c also. I should have made that clear.
There is not a huge difference between your scheme and mine. My
question is, how do you handle (d)?
The way I see it, both schemes remove the ambiguity. Mine retains a
single deconfig file and a single 'make menuconfig' for each board.
Yours feels more like building independent U-Boot images.
Regards,
Simon
