[PATCH 1/2] bloblist: fix the overriding of fdt from bloblist

[Raymond Mao]

Hi Simon,

On Fri, 28 Mar 2025 at 10:26, Simon Glass <sjg at chromium.org> wrote:
>
> Hi Raymond,
>
> On Fri, 28 Mar 2025 at 08:17, Raymond Mao <raymond.mao at linaro.org> wrote:
> >
> > Hi Simon,
> >
> > On Fri, 28 Mar 2025 at 07:34, Simon Glass <sjg at chromium.org> wrote:
> > >
> > > Hi Raymond,
> > >
> > > On Thu, 27 Mar 2025 at 17:13, Raymond Mao <raymond.mao at linaro.org> wrote:
> > > >
> > > > When a bloblist is valid and contains fdt, it explicitly means
> > > > a previous boot stage is passing transfer list compliant with
> > > > Firmware Handoff specification, thus the fdt from bloblist should
> > > > not be overridden with the ones from board or env variables.
> > >
> > > Why is that? The board can choose to override it, if it wishes, but in
> > > general, if gd->fdt_blob is already set up, it should return -EEXIST
> > > from board_fdt_blob_setup().
> > >
> > First, if a board is running in a "stand-alone" mode, there should not
> > be a transfer list passed from the previous boot stage.
> > Secondly, overriding the transfer list with the env variables does not
> > make sense, since booti, bootm and bootefi are actually using the env
> > variables to get the fdt when launching to the kernel.
> > We need to do the opposite way - override the env variable with the
> > one pointing to the bloblist fdt (See my patch [2/2]), then all boot
> > commands can work with the transfer list.
>
> OK, but now we are going back to the OF_BLOBLIST thing that I did 18
> months ago and ended up being the major reason I had to create my own
> U-Boot tree just to get my boards working.
>
> Anyway, Tom has agreed to let me maintain bloblist (and maybe fdt?)
> again, so I am going to send a series to 'clean this up' as Ilias
> would say. Let's see if that passes muster, because I do agree with
> you that if the devicetree is in the bloblist, it should be
> definitive.
>
> Re your second point, do you know why we have fdt_addr? Is it just for
> the distro scripts? I'm wondering if we could restrict the use of
> fdt_addr to just the places that actually need to use environment
> variables.
>

I understand that there is a clean-up plan from you, so this time I am
just trying to minimize the changes (as you can see, just a few lines)
to make the transfer list work again.
I am also working on the OP-TEE repo project to enable qemu v8 build
with transfer list enabled, so users can just use a single command to
test the Firmware Handoff feature from TF-A to kernel.
But since 70fe23859437, it is broken in U-Boot due to the overriding
of the fdt, I made this hotfix in order to let us have the feature
work again before the upcoming release.

Regards,
Raymond


> Regards,
> SImon