[U-Boot] Booting non devicetree enabled kernels using u-boot build with CONFIG_OF_LIBFDT ?

[Tom Rini]

On Thu, Nov 13, 2014 at 07:38:50PM +0100, Hans de Goede wrote:
> Hi,
> 
> On 11/13/2014 07:34 PM, Tom Rini wrote:
> > On Thu, Nov 13, 2014 at 07:08:59PM +0100, Hans de Goede wrote:
> >> Hi all,
> >>
> >> So as you know I've been working on getting mainline u-boot to boot the
> >> older android derived linux-sunxi kernels, as some people need features
> >> not yet in mainline, and I would like there to be only one u-boot for both.
> >>
> >> I had this working a while ago, but recently it broke, this is caused by
> >> config_distro_defaults.h setting CONFIG_OF_LIBFDT, if I undef that
> >> after including config_distro_defaults.h things work again.
> >>
> >> I do not know if CONFIG_OF_LIBFDT is a recent addition to config_distro_defaults.h,
> >> or if something else broke things. But if I do not undef it, boot fails with:
> >>
> >> sun7i# bootm start 0x48000000
> >> ## Booting kernel from Legacy Image at 48000000 ...
> >>    Image Name:   Linux-3.4.75.sun7i+
> >>    Image Type:   ARM Linux Kernel Image (uncompressed)
> >>    Data Size:    3966672 Bytes = 3.8 MiB
> >>    Load Address: 40008000
> >>    Entry Point:  40008000
> >>    Verifying Checksum ... OK
> >> Could not find a valid device tree
> > 
> > My hunch is that we've got more fall-out from Simon's re-org of the
> > bootm code ages ago.  It should be valid to try and boot a kernel
> > without a device tree and other parts of the code base (for example
> > arch/arm/lib/bootm.c) still do a FDT-or-ATAGS dance for example.
> 
> That is good news, because ideally upstream u-boot build with
> OLD_SUNXI_KERNEL_COMPAT should be able to boot old disk images without
> needing them to modify their boot.scr, which requiring bootm 0xfoo - -
> would do.
> 
> So maybe check if there is a third argument to bootm, and if there
> is not still try the dance for finding one appended in various ways,
> and if that fails continue normally (where as with the third
> argument present this of course needs to stay an error) ?

So first, I have to take it back.  This isn't a behavior change
introduced by Simon's re-org (Sorry Simon!).  This is a real long
standing "feature".   I am agreeable to doing whatever the lowest impact
change would be to allow a non-DT tree to boot with CONFIG_OF_LIBFDT
set.   I'm thinking we turn the error into a warning (so that it's still
clear to the user that they booted without a DT, for when they didn't
mean to do that) and instead of a hang we just don't do the follow-up
steps.  That should let all the existing scripts work, yes?

-- 
Tom
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