Hi François, On Sat, 4 Dec 2021 at 04:06, François Ozog <francois.o...@linaro.org> wrote: > > Hi Simon > > Le sam. 4 déc. 2021 à 02:02, Simon Glass <s...@chromium.org> a écrit : >> >> Hi Heinrich, >> >> On Fri, 3 Dec 2021 at 13:28, Heinrich Schuchardt <xypron.g...@gmx.de> wrote: >> > >> > On 12/3/21 9:13 PM, Simon Glass wrote: >> > > Hi Heinrich, >> > > >> > > On Fri, 3 Dec 2021 at 06:09, Heinrich Schuchardt <xypron.g...@gmx.de> >> > > wrote: >> > >> >> > >> On 12/3/21 13:34, Heinrich Schuchardt wrote: >> > >>> On 12/2/21 16:58, Simon Glass wrote: >> > >>>> At present some of the ideas and techniques behind devicetree in >> > >>>> U-Boot >> > >>>> are assumed, implied or unsaid. Add some documentation to cover how >> > >>>> devicetree is build, how it can be modified and the rules about using >> > >>>> the various CONFIG_OF_... options. >> > >>>> >> > >>>> Signed-off-by: Simon Glass <s...@chromium.org> >> > >>>> Reviewed-by: Marcel Ziswiler <marcel.ziswi...@toradex.com> >> > >>>> --- >> > >>>> This patch attracted quite a bit of discussion here: >> > >>>> >> > >>>> https://patchwork.ozlabs.org/project/uboot/patch/20210909201033.755713-4-...@chromium.org/ >> > >>>> >> > >>>> >> > >>>> I have not included the text suggested by François. While I agree that >> > >>>> it would be useful to have an introduction in this space, I do not >> > >>>> agree >> > >>>> that we should have two devicetrees or that U-Boot should not have its >> > >>>> own >> > >>>> things in the devicetree, so it is not clear to me what we should >> > >>>> actually >> > >>>> write. >> > >>>> >> > >>>> The 'Devicetree Control in U-Boot' docs were recently merged and these >> > >>>> provide some base info, for now. >> > >>>> >> > >>>> 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 >> > >>>> >> > >>>> Changes in v5: >> > >>>> - Bring into the OF_BOARD series >> > >>>> - Rebase to master and drop mention of OF_PRIOR_STAGE, since removed >> > >>>> - Refer to the 'control' DTB in the first paragraph >> > >>>> - Use QEMU instead of qemu >> > >>>> >> > >>>> Changes in v3: >> > >>>> - Clarify the 'bug' refered to at the top >> > >>>> - Reword 'This means that there' paragraph to explain U-Boot-specific >> > >>>> things >> > >>>> - Move to doc/develop/devicetree now that OF_CONTROL is in the docs >> > >>>> >> > >>>> Changes in v2: >> > >>>> - Fix typos per Sean (thank you!) and a few others >> > >>>> - Add a 'Use of U-Boot /config node' section >> > >>>> - Drop mention of dm-verity since that actually uses the kernel >> > >>>> cmdline >> > >>>> - Explain that OF_BOARD will still work after these changes (in >> > >>>> 'Once this bug is fixed...' paragraph) >> > >>>> - Expand a bit on the reason why the 'Current situation' is bad >> > >>>> - Clarify in a second place that Linux and U-Boot use the same >> > >>>> devicetree >> > >>>> in 'To be clear, while U-Boot...' >> > >>>> - Expand on why we should have rules for other projects in >> > >>>> 'Devicetree in another project' >> > >>>> - Add a comment as to why devicetree in U-Boot is not 'bad design' >> > >>>> - Reword 'in-tree U-Boot devicetree' to 'devicetree source in U-Boot' >> > >>>> - Rewrite 'Devicetree generated on-the-fly in another project' to >> > >>>> cover >> > >>>> points raised on v1 >> > >>>> - Add 'Why does U-Boot have its nodes and properties?' >> > >>>> - Add 'Why not have two devicetrees?' >> > >>>> >> > >>>> doc/develop/devicetree/dt_update.rst | 555 >> > >>>> +++++++++++++++++++++++++++ >> > >>>> doc/develop/devicetree/index.rst | 1 + >> > >>>> 2 files changed, 556 insertions(+) >> > >>>> create mode 100644 doc/develop/devicetree/dt_update.rst >> > >>>> >> > > [..] >> > > >> > >>>> + >> > >>>> +- The other project may not provide a way to support U-Boot's >> > >>>> requirements for >> > >>>> + devicetree, such as the /config node. Note: On the U-Boot mailing >> > >>>> linst, this >> > >>> >> > >>> Even if you remove these lines in 17/25 I would prefer not to introduce >> > >>> typos here: >> > >>> >> > >>> %s/linst/list/ >> > >>> >> > > >> > > OK I can fix that. >> > > >> > > [..] >> > > >> > >>>> +Normally, supporting U-Boot's features is trivial, since the >> > >>>> devicetree compiler >> > >>>> +(dtc) can compile the source, including any U-Boot pieces. So the >> > >>>> burden is >> > >>>> +extremely low. >> > >>>> + >> > >>>> +In this case, the devicetree in the other project must track U-Boot's >> > >>>> use of >> > >>>> +device tree, so that it remains compatible. See `Devicetree in >> > >>>> another project`_ >> > >>>> +for reasons why. >> > >>> >> > >>> Did you ever ask the QEMU community what they think about your ideas? >> > >>> What was the reply? >> > >> >> > >> Looking at the thread >> > >> https://lore.kernel.org/all/20210926183410.256484-1-...@chromium.org/ >> > >> the QEMU project said NAK. This matches the expectation that I expressed >> > >> repeatedly. >> > >> >> > >> Why don't you mention the QEMU reply in this patch series and adjust >> > >> your design accordingly? >> > > >> > > The QEMU maintainer may react when he sees a problem. >> > >> > Why are you unwilling to admit the problem? QEMU will never support >> > U-Boot specific stuff. >> > >> > Please, develop concepts that solve U-Boot's needs within U-Boot. >> >> So you are saying that because QEMU wrote it's devicetree support with >> Linux in mind, we should, what...? Spent 500ms merging devicetrees >> before relocation? Move back to platdata? Delete driver model? Rewrite >> U-Boot? > > heinrich did not said that. He said that QEMU team said it doesn’t want to > deal with specifics of *any* payload, be it a Linux kernel, a hypervisor, > TFA, U-Boot, Coreboot or *Boot.
Except that QEMU does deal with the Linux specifics. See the qemu-arm.dts file in this series, which is directly taken from QEMU. It has linux, properties and a chosen node. I wasn't even suggesting that it deal with U-Boot specifics, just provide a way to adjust the DT that it creates out of whole cloth. > In that spirit, TFA made sure they can have the DT they need in the FIP. > I add now: U-Boot when loaded by SPL in QEMU can follow the same pattern and > have a FIT contain U-Boot and the control DTs it needs and deal with it. > Binman should be used to assemble that image. Something along those lines… Yes, except U-Boot cannot even boot from SPL without some DT properties. See my patch https://patchwork.ozlabs.org/project/uboot/patch/20211101011734.1614781-15-...@chromium.org/ I have been working on this for years. Trust me... Regards, Simon >> >> >> U-Boot works quite nicely as it is. The problem is that people are >> still coming to terms with U-Boot's right to use the devicetree. This >> could take a few more years, I think, or it may never happen. Most >> people don't even know how U-Boot works. We just need to be patient. >> >> Regards, >> Simon >> >> >> > >> > Best regards >> > >> > Heinrich >> > >> > > >> > > I have already clearly stated that there is no way we are have two >> > > control DTBs. The overlay is also unworkable and unnecessary. That is >> > > why I put so much effort into this patch, after all. >> >> >> > > >> > > So for now, people will just have to deal with what QEMU provides. I >> > > sent a patch to resolve the problem which can be accepted at any point >> > > if people complain enough. So far only François has offered support >> > > for it. >> > > >> > > Regards, >> > > Simon >> > > >> > > > -- > François-Frédéric Ozog | Director Business Development > T: +33.67221.6485 > francois.o...@linaro.org | Skype: ffozog >