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

[Michal Simek]

On 10.1.2017 14:08, Alexander Graf wrote:
> 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?

Only that one which has it enabled.
I expect most of boards with has OF_CONTROL enabled are not using ATAG.

Thanks,
Michal