Hi Mark, On Thu, 2 Dec 2021 at 12:22, Mark Kettenis <mark.kette...@xs4all.nl> wrote: > > > From: Simon Glass <s...@chromium.org> > > Date: Thu, 2 Dec 2021 11:53:53 -0700 > > > > Hi Mark, > > > > On Thu, 2 Dec 2021 at 11:47, Mark Kettenis <mark.kette...@xs4all.nl> wrote: > > > > > > > From: Simon Glass <s...@chromium.org> > > > > Date: Thu, 2 Dec 2021 11:21:22 -0700 > > > > > > > > Hi Mark, > > > > > > > > On Thu, 2 Dec 2021 at 11:15, Mark Kettenis <mark.kette...@xs4all.nl> > > > > wrote: > > > > > > > > > > > From: Ilias Apalodimas <ilias.apalodi...@linaro.org> > > > > > > Date: Thu, 2 Dec 2021 19:03:46 +0200 > > > > > > > > > > > > On Thu, 2 Dec 2021 at 18:38, 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. > > > > > > > > > > > > So this is a key point for me and the reason I completely disagree > > > > > > with this approach. This proposal is working in the *exact* > > > > > > opposite > > > > > > direction and we'll never be able to get rid of device trees from > > > > > > U-Boot, even if at some point they move out of the kernel to a > > > > > > 'common' repo'. I'll just repeat what I've been saying since v1. > > > > > > Personally I'd be way happier if we could figure out were the > > > > > > specific > > > > > > U-Boot config nodes are needed and when are they needed. Based on > > > > > > what we figure out we could, pick up the device tree from a previous > > > > > > state bootloader and fix it up with our special nodes before we > > > > > > start > > > > > > using it, using internal DTS files (compiled to .dtbos or similar) > > > > > > that indeed belong in the u-boot tree. > > > > > > > > > > I don't think it makes sense to put stuff in the DT that is specific > > > > > for U-Boot only to pull it out moments later. Maybe it does make some > > > > > sense to do this to pass information between TPL/SPL and U-Boot > > > > > proper. But otherwise you can just use global variables... > > > > > > > > > > Now I just ran into an issue on Apple M1 that may have some relevance > > > > > here. I'm adding support for power domains and the serial port > > > > > requires certain power domains to be on. Since the serial port is > > > > > initialized in the pre-relocation phase this means that the device > > > > > tree nodes for the power domain controllers need to have the > > > > > "u-boot,dm-pre-reloc" property on them. Otherwise the DM code won't > > > > > be able to bind the power domain controller driver in this phase and > > > > > binding the serial port driver itself will fail. Which makes U-Boot > > > > > hang without any visible output on the serial console. > > > > > > > > > > Within the Asahi Linux group we're currently discussing how to solve > > > > > this. We could just add the "u-boot,dm-pre-reloc" properties in the > > > > > device trees that we're going to distribute as part of m1n1 (the > > > > > "bootloader" than embeds U-Boot). Or we can write some code that adds > > > > > those properties to the device tree nodes that are dependencies for > > > > > the serial port. > > > > > > > > > > I don't think the suggestion of applying an overlay embedded in U-Boot > > > > > would work here. The code applying the overlay would need to run very > > > > > early on in the pre-relocation phase. We'd also have to include > > > > > overlays for all the models that Apple offers and pick the right one. > > > > > And if a new model appears we can no longer just add a new device tree > > > > > to m1n1. > > > > > > > > Well put. > > > > > > > > > > > > > > But maybe there is a case where the overlay approach would make > > > > > sense... > > > > > > > > There might be, but I haven't found it yet. > > > > > > > > BTW I suggest we figure out how to upstream the binding for this. I > > > > will see if I can send a patch to start the process. The last patch > > > > didn't get any comments though. > > > > > > > > In the interim there is probably no choice but to add the properties > > > > into the m1n1 project. Of course, for development, you could just turn > > > > off OF_BOARD, with my series applied. Which is a lot of the point of > > > > all of this discussion... > > > > > > And that is exactly why I don't see the point of this series. There > > > is no chance of that working. The device tree that is currently in > > > the U-Boot tree (essentially because you made me add one) is only a > > > template that gets modified by m1n1 to account for hardware > > > characteristics (amount of memory, cores that are actually enabled, > > > MAC addresses, WiFi antenna configuration, etc. etc.). If I flip > > > OF_BOARD U-Boot would simply not work. > > > > > > The way I do development is that I simply build a device tree, build > > > U-boot and upload them over serial to m1n1 running on the device. I > > > currently do build my device trees out of the U-Boot tree, but the > > > main reason for that is because the Linux development model means that > > > too many of the device tree patches are still in flight. I often use > > > the device tree from a different U-Boot repository clone than the one > > > I do the actual U-Boot development in anyway. > > > > Yes and I think you have made my point. That is all I am saying. I am > > not claiming that U-Boot needs to be the golden repo for the .dts, > > just that it should have something suitable that works well enough for > > development, and can be modified and updated as development > > progresses. > > No you are missing my point. I'm only doing it this way because the > Linux development model is so broken that it takes months for patches > posted on the mailing list to end up in a somewhat official source > tree and I would go bat-shit crazy having to deal with all the merges > and rebasing going on. > > If there was a separate device tree project, I would very much prefer > to use that and make device tree changes there such that I could > submit any additions to the canonical sources. I'm currently spending > too much of my development time synching the device trees in my U-Boot > tree with what's going on on the Linux side.
Right, exactly. I have exactly the same problem and so do other people working with U-Boot. At least we have a work-around. Regards, Simon
