[U-Boot] [RFC PATCH] arm: bootm: Boot kernel with U-Boot's FDT blob

[Alexander Graf]

On 01/10/2017 02:05 PM, Michal Simek wrote:
> On 10.1.2017 14:02, Alexander Graf wrote:
>> On 01/10/2017 01:58 PM, Michal Simek wrote:
>>> U-Boot configured via DTB can use the same DTB for booting the kernel.
>>> When OF_CONTROL is used fdtcontroladdr is setup and can be use for boot.
>>>
>>> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
>>> ---
>>>
>>> Didn't check if there is any side effect or not but it looks weird when
>>> you have DT driver u-boot that you have to load dtb again.
>> I agree, and I think it's very reasonable to try and use the same device
>> tree for U-Boot and Linux.
>>
>> I'm not sure it's a great idea to check for the builtin device tree
>> after ATAGs though. Shouldn't we prefer the built-in one over ATAGs?
> No problem to do it. The reason why I have done it in this way was not
> to change behavior for existing platforms.
>
> u-boot is also doing some automatic updates which can require fdt resize
> but I didn't check if resize can be done in that space where build-in
> dtb is.

Good point. It probably makes sense to copy it out, as we do in the EFI 
boot path (see the copy_fdt() call):

   https://github.com/trini/u-boot/blob/master/cmd/bootefi.c#L173

I also agree on the default behavior change problem. But in the patch as 
is, won't most boards just fall back to ATAG boot?


Alex