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. 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… > > 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
