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

[Hans de Goede <hdegoede@redhat.com>]

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) ?

Regards,

Hans