Hi Tom,
On Tue, 7 Dec 2021 at 09:07, Tom Rini trini@konsulko.com wrote:
On Tue, Dec 07, 2021 at 09:02:23AM -0700, Simon Glass wrote:
Hi Tom,
On Tue, 7 Dec 2021 at 08:39, Tom Rini trini@konsulko.com wrote:
On Tue, Dec 07, 2021 at 08:33:49AM -0700, Simon Glass wrote:
Hi Andre,
On Tue, 7 Dec 2021 at 08:25, Tom Rini trini@konsulko.com wrote:
On Tue, Dec 07, 2021 at 12:59:48AM +0000, Andre Przywara wrote:
On Mon, 6 Dec 2021 17:11:52 -0700 Simon Glass sjg@chromium.org wrote:
> Sync these files, obtained from Linux v5.15.
Sorry, but this would be wrong. How do you know which board it is? Highbank or Midway? We use the same binary for both, and decide either by the DT nodes we find in DRAM or by some autodetection (Cortex-A9 vs. Cortex-A15) if there are differences. The memory size would possibly be wrong (it's a DIMM slot). If you need *some* DT for build reasons, whatever, but at least go with the empty stub.
And I still don't get this whole development argument: Why would anyone need some random or partial DT sample in the U-Boot tree to do development? If people develop a driver, the document to code against is the *binding* documentation, which describes what to expect from the DT nodes. Then you *test* it against an actual tree, but on the actual hardware, in which case you get the actual DTB, from the board. If a developer needs to take a sneak peek into an actual DTB, there are so many simple ways to do that: QEMU's dumpdtb, RPi's SD card content, U-Boot's "fdt addr $fdtcontroladdr; fdt print", the kernel's /sys/firmware/devicetree/base, ... When you port U-Boot to a board, getting hands on the actual DT is probably the least of your problems.
So why would we need some mostly wrong DTs in the U-Boot tree? It seems to suggest that you can hack the DT to make things work, but this sounds bonkers, as the real DTB comes from somewhere else (SPI flash, SD card, generated based on command line), and patching U-Boot's copy to make things work is just wishful thinking.
I can see the hacker's desire to play around with the DTB from time to time (What happens if the GPIO is wrong? Can we deal with two instances of the same device?), but for those experiments there are plenty of ways to achieve this - and be it temporarily replacing the empty DT stub. I just feel that bending the (board's) DT design ideas for a hacker's pleasure is not justified.
Andre, if you'd like to attend the U-Boot contributor call in an hour, please do.
This, largely, is why I still don't understand or agree with the direction this series is taking platforms that currently use CONFIG_OF_BOARD=y today.
I am not sure what else to do at this point. For real boards, there has to be some base devicetree somewhere that is put into the firmware.
Yes, there is. It's in the firmware on the hardware. That's where it lives.
Just because it changes at runtime does not change that fact. So we can inject any DT into the firmware and the same transformations should happen. We just need to have the same one as everyone else uses.
I think you're missing the point here still. The DT lives IN the firmware. In that an official dts for that firmware exists somewhere, I gather it's not public, because it doesn't have to be.
That was my question to François a while back and I gathered from the answer that everything is public / open-source.
We already know every DT-using platform doesn't have public DTS files, there's the broadcom platform that was talked about an iteration or three back.
Also this is just copied from Linux, which I understand you were comfortable with.
I also said when the custodian doesn't object.
So what is the fallback? Another empty tree?
If it isn't public, why do we have the board in U-Boot? If one board is public and the other isn't, we should only care about the public board, IMO. I hope I just have the wrong end of the stick here.
I'm elaborating on this in a draft right now still, but we support it because it works? That's part of the point of device trees, the information gets provided at run time.
We cannot support that stuff in mainline. It is up to the maintainer to keep things working.
Regards, Simon