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

[Michal Simek]

On 10.1.2017 18:52, Stephen Warren wrote:
> On 01/10/2017 09:58 AM, Alexander Graf wrote:
>> On 01/10/2017 05:47 PM, Ryan Harkin wrote:
>>> On 10 January 2017 at 16:35, Alexander Graf <agraf at suse.de> wrote:
>>>> On 01/10/2017 05:31 PM, york sun wrote:
>>>>> On 01/10/2017 05:02 AM, 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.
>>>>>>
>>> Would this prevent the user loading a DTB into ram and using bootm to
>>> over-ride the built-in DTB?
>>>
>>> I have a background task to refactor u-boot support for ARM Ltd
>>> boards. One of many options I was considering was to have a minimal
>>> DTB to configure the platform with only the nodes needed for u-boot.
>>> The ARM Ltd device trees fluctuate so much, I wouldn't be able to
>>> commit to one DTB that will work forever...
>>
>> No, it's only meant as a fallback when no manual device tree is
>> provided. In an ideal world however, device trees are static and
>> complete, so you could just put a final dt into U-Boot and have it
>> propagated all the way through.
> 
> Can the commit message be updated to reflect this? From the commit
> message, it sounds like the control FDT will always be used. Something
> like "arm: bootm: fall back to U-Boot's FDT blob when booting kernel"
> would sound a lot less scary.

Sure not a problem to change it. Plus there must be a solution for c&p
dtb to location where can be resized.

Thanks,
Michal