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Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree
From: |
Simon Glass |
Subject: |
Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree |
Date: |
Mon, 27 Sep 2021 09:17:51 -0600 |
Hi Peter,
On Mon, 27 Sept 2021 at 02:48, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Sun, 26 Sept 2021 at 19:55, Simon Glass <sjg@chromium.org> wrote:
> > In the case of U-Boot at least, it uses the devicetree for
> > configuration (it is a boot loader, so there is no user space to
> > provide configuration). So the current setup is not sufficient to boot
> > it correctly in all cases. On the other hand, the 'virt' feature is
> > very useful for testing U-Boot, so it would be great to be able to
> > support this.
>
> So what is missing in the QEMU-provided DTB that it needs?
Quite a lot. Here are some examples:
U-Boot has limited pre-relocation memory so tries to avoid
binding/probing devices that are not used before relocation:
https://u-boot.readthedocs.io/en/latest/develop/driver-model/design.html#pre-relocation-support
There is a configuration node (which is likely to change form in
future releases, but will still be there)
https://github.com/u-boot/u-boot/blob/master/doc/device-tree-bindings/config.txt
Then there are various features which put things in U-Boot's control
dtb, such as verified boot, which adds public keys during signing:
https://github.com/u-boot/u-boot/blob/master/doc/uImage.FIT/signature.txt#L135
More generally, the U-Boot tree has hundreds of files which add
properties for each board, since we try to keep the U-Boot-specific
things out of the Linux tree:
$ find . -name *u-boot.dtsi |wc -l
398
Quite a bit of this is to do with SPL and so far it seems that QEMU
mostly runs U-Boot proper only, although I see that SPL is starting to
creep in too in the U-Boot CI.
So at present QEMU is not able to support U-Boot fully. It would be
great to add this as we use QEMU heavily in CI testing, e.g. see the
second column here:
https://source.denx.de/u-boot/custodians/u-boot-dm/-/pipelines/9260
Regards,
Simon
- [PATCH] hw/arm/virt: Allow additions to the generated device tree, Simon Glass, 2021/09/26
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Peter Maydell, 2021/09/26
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Simon Glass, 2021/09/26
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Peter Maydell, 2021/09/27
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree,
Simon Glass <=
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Peter Maydell, 2021/09/27
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Simon Glass, 2021/09/27
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Peter Maydell, 2021/09/27
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Simon Glass, 2021/09/27
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Peter Maydell, 2021/09/28
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Simon Glass, 2021/09/28
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Peter Maydell, 2021/09/29
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Simon Glass, 2021/09/29
- Re: [PATCH] hw/arm/virt: Allow additions to the generated device tree, Andrew Jones, 2021/09/29