Hi Tom, On Thu, 2 Dec 2021 at 09:59, Tom Rini <tr...@konsulko.com> wrote: > > On Thu, Dec 02, 2021 at 09:49:51AM -0700, Simon Glass wrote: > > Hi Tom, > > > > On Thu, 2 Dec 2021 at 09:38, Tom Rini <tr...@konsulko.com> wrote: > > > > > > On Thu, Dec 02, 2021 at 05:33:53PM +0100, François Ozog wrote: > > > > Hi Simon > > > > > > > > Le jeu. 2 déc. 2021 à 17:00, Simon Glass <s...@chromium.org> a écrit : > > > > > > > > > With Ilias' efforts we have dropped OF_PRIOR_STAGE and OF_HOSTFILE so > > > > > there are only three ways to obtain a devicetree: > > > > > > > > > > - OF_SEPARATE - the normal way, where the devicetree is built and > > > > > appended to U-Boot > > > > > - OF_EMBED - for development purposes, the devicetree is embedded > > > > > in > > > > > the ELF file (also used for EFI) > > > > > - OF_BOARD - the board figures it out on its own > > > > > > > > > > The last one is currently set up so that no devicetree is needed at > > > > > all > > > > > in the U-Boot tree. Most boards do provide one, but some don't. Some > > > > > don't even provide instructions on how to boot on the board. > > > > > > > > > > The problems with this approach are documented in another patch in > > > > > this > > > > > series: "doc: Add documentation about devicetree usage" > > > > > > > > > > In practice, OF_BOARD is not really distinct from OF_SEPARATE. Any > > > > > board > > > > > can obtain its devicetree at runtime, even it is has a devicetree > > > > > built > > > > > in U-Boot. This is because U-Boot may be a second-stage bootloader > > > > > and its > > > > > caller may have a better idea about the hardware available in the > > > > > machine. > > > > > This is the case with a few QEMU boards, for example. > > > > > > > > > > So it makes no sense to have OF_BOARD as a 'choice'. It should be an > > > > > option, available with either OF_SEPARATE or OF_EMBED. > > > > > > > > > > This series makes this change, adding various missing devicetree files > > > > > (and placeholders) to make the build work. > > > > > > > > > > Note: If board maintainers are able to add their own patch to add the > > > > > files, some patches in this series can be dropped. > > > > > > > > > > It also provides a few qemu clean-ups discovered along the way. The > > > > > qemu-riscv64_spl problem is fixed. > > > > > > > > > > [1] > > > > > https://patchwork.ozlabs.org/project/uboot/patch/20210919215111.3830278-3-...@chromium.org/ > > > > > > > > > > Changes in v6: > > > > > - Fix description of OF_BOARD so it refers just to the current state > > > > > - Explain that the 'two devicetrees' refers to two *control* > > > > > devicetrees > > > > > - Expand the commit message based on comments > > > > > - Expand the commit message based on comments > > > > > > > > You haven’t addressed any concerns expressed on the mailing list.so I am > > > > not in favor of this new version either. > > > > If you make a version without « fake DTs » as you name them, there are > > > > good > > > > advances in the documentation and other areas that would be better in > > > > mainline…. > > > > If I am the only one thinking this way and the patch can be accepted, I > > > > would love there is a warning in capital letters at the top of the DTS > > > > fake > > > > files that explains the intent of this fake DT, the possible outcomes of > > > > not using the one provided by the platform and the right way of dealing > > > > with DTs for the platform. > > > > > > This is the part that I too am still unhappy about. I do not want > > > reference or fake or whatever device trees in the U-Boot source tree. > > > We should be able to _remove_ the ones we have, that are not required, > > > with doc/board/...rst explaining how to get / view one. Not adding > > > more. > > > > I understand you don't like it and that others don't as well. I wish > > it had not come to this. > > > > However we are only talking about 10 boards, three of which don't even > > have a devicetree anywhere I can find. > > > > I think on balance this is a substantial clean-up. I am happy to add > > whatever caveats and documentation people want to clarify what is > > going on here. I'm happy to look at future options where the > > devicetree is hosted elsewhere, so long as it is trivial to build it > > within U-Boot for development purposes. > > > > I'll also note that the bootstd series shows the devicetree source: > > > > Core: 246 devices, 88 uclasses, devicetree: board > > > > But for now, I still feel this is the best path forward. > > I'm not sure how to proceed here. The reviews are rather strongly > against the "include a device tree that won't be used". The use case of > "but for development someone might need to modify the device tree" is > handled by platforms documenting where / how to get the real one. We > should even update the Kconfig help to note that if you enable this your > board docs MUST explain where the device tree can be seen (or have some > legal reason you think it's OK to not...).
Right, we can do lots of things as we have discussed. I am very willing to work on these and make sure it is hard to do the thing. But this series is long enough already. It is more than just development. A devicetree is needed for binman to work, even if it is empty. The documentation idea doesn't really work, as I think I have proven by the difficulty in getting this series together. An automated mechanism that runs in CI might be acceptable, but that is in the future. For now, I believe it just HAS to be in-tree. > > And yes, we're "only" talking about 10 platforms, which include things > like the "everyone" has one Pi family, the extraordinarily flexible (and > so easy for the reference device tree to be very wrong) QEMU families > and then platforms that are including a dts in-tree now because they > were told that was required. Actually it is only rpi4 that doesn't have an in-tree DT. There is actually no reason for it not to, e.g. Linux has it. Why not U-Boot? The argument is the same. Most QEMU boards have an in-tree devicetree. It is only ARM (now copied by RISC-V) which doesn't. > > How about adjusting the make logic so that if a tree isn't found, we use > a dummy minimal valid dts file? This is what I have done for the boards where I could not figure out how to get any sort of DT, yes. But I don't think that should be the default. Regards, Simon
