On Thu, Feb 13, 2025 at 07:33:20AM -0700, Simon Glass wrote: > Hi Tom, > > On Thu, 13 Feb 2025 at 07:15, 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. > > > > > > 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. > > > > Here is the big problem I see with your proposal. Today our Kbuild and > > kconfig support is very much out of date. And while my attempts to > > resync them together haven't worked, I believe it comes down to how we > > build *pl targets today, at least in part, because that's just not > > a thing upstream has to do. What you're proposing here will make any > > future resyncs even harder as more of the code will diverge from > > upstream (as seen in your previous RFC series). > > Yes, that's true, but mostly in kconfig. I would be willing to resync > kconfig with Linux, if that helps.
Yes, re-syncing scripts/kconfig to v6.13 (as a stand alone series) would be helpful, thanks. > For kbuild, my series doesn't do much there. I could perhaps offer a > resync of fixdep.c ? That's another part of the infrastructure that is out of date, yes. > Did Linaro show any interest in taking on Kbuild? Linux just has a > huge amount of build-code now. What problems do you have with U-Boot's > current Kbuild? Yes, it's somewhere on various people's "would like to do" list. And in terms of problems: - clang is broken for everything except sandbox I believe - clang + LTO never worked for us - Our dtc ignore warning flags are well out of date (and harder to sync up with) - All of the general fixes with the Kbuild logic post v4.20 are just missing. That's just off the top of my head. -- Tom
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