Problem with U-boot | Configuration Signature not being checked while booting

[Tom Rini]

On Fri, Sep 17, 2021 at 10:19:18AM -0600, Simon Glass wrote:
> Hi Mark,
> 
> On Wed, 15 Sept 2021 at 05:52, Mark Kettenis <mark.kettenis at xs4all.nl> wrote:
> >
> > > From: Simon Glass <sjg at chromium.org>
> > > Date: Wed, 15 Sep 2021 04:13:24 -0600
> >
> > Hi Simon,
> >
> > > Hi Mark,
> > >
> > > On Sat, 11 Sept 2021 at 13:18, Mark Kettenis <mark.kettenis at xs4all.nl> wrote:
> > > >
> > > > > From: Moiz Imtiaz <moizimtiaz1 at gmail.com>
> > > > > Date: Sat, 11 Sep 2021 23:19:05 +0500
> > > > >
> > > > > Hi Simon,
> > > > >
> > > > > Thanks for the reply.  I already followed the steps mentioned in
> > > > > "doc/uImage.FIT/beaglebone_vboot.txt".
> > > > >
> > > > > >I wonder if rpi is not using the devicetree compiled with U-Boot, but
> > > > > instead one provided by the earlier-stage firmware?
> > > > >
> > > > > Not sure, but seems like this is the case. I checked and there isn't any
> > > > > dtb or dts for rpi4 (bcm2711-rpi-4-b) in arc/arm/dts in u-boot. I tried to
> > > > > add the dtb and other dts dtsi
> > > > > <https://github.com/raspberrypi/linux/tree/rpi-5.10.y/arch/arm64/boot/dts/broadcom>files
> > > > > from the raspberry pi Linux and compile them with CONFIG_OF_SEPARATE and
> > > > > CONFIG_OF_EMBED (one at a time) *but it couldn't even boot the U-Boot and
> > > > > it would just give a blank screen*. I wonder why there isn't any device
> > > > > tree in the U-boot repo for RPI4. Is U-boot control FDT not supported by
> > > > > RPI4?
> > > >
> > > > The issue with the rpi4 is that the addresses of devices move around
> > > > based on the version of the Raspberry Pi firmware you're using.  And
> > > > possibly on the amount of memory on the board as well.  So U-Boot
> > > > pretty much has to use the device tree passed by the firmware since
> > > > the device tree in the U-Boot tree would be wrong for many
> > > > combinations of firmware and hardware.
> > > >
> > > > Simon, this sort of thing is exactly the reason why I think the idea
> > > > of having all U-Boot configuration information in a single device tree
> > > > with the hardware description doesn't work everywhere.
> > >
> > > >From my reading of this thread, it rather reinforces the need to
> > > provide a way to give U-Boot the config it needs, in the devicetree.
> >
> > As long as that configuration is optional, yes, maybe.
> >
> > > It seems that rpi is actually OK in this regard. If you think about
> > > it, it would be pretty hopeless if first-stage firmware assumed that
> > > it could provide a devicetree to whatever is next.
> >
> > Not hopeless.  If that device tree provides a hardware description
> > that is complete enough to boot Linux, it should be good enough to run
> > U-Boot.
> 
> Not in general. I hope I have covered this in enormous detail in the
> devicetree patch. But if you don't need verified boot, SPL or some
> other feature that needs config, then perhaps you will get away with
> it.

Wait, why does SPL _need_ it?  If something provides us with a device
tree, we don't need u-boot,dm-spl as that's used to filter nodes in to a
smaller DT to use.  Dealing with u-boot,dm-pre-reloc could be trickier,
but means whatever loaded us needs to have enabled any early clocks we
need.  But even then, it's just going to be output related?  And some
"was already configured" path could be used.

-- 
Tom
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