[U-Boot] [PATCH v5 10/13] tegra: Use a U-Boot-specific .dtsi file

[Stephen Warren]

On 11/28/2016 03:09 PM, Simon Glass wrote:
> Hi Stephen,
>
> On 17 November 2016 at 12:45, Stephen Warren <swarren at wwwdotorg.org> wrote:
>>
>> On 11/16/2016 06:13 PM, Simon Glass wrote:
>>>
>>> With the new device-tree rules it is possible to put device-tree changes
>>> needed by U-Boot into their own file. As an example of this approach, move
>>> Tegra over to use it.
>>
>>
>> Sounds like a good idea.
>>
>>> diff --git a/arch/arm/dts/tegra20-u-boot.dtsi b/arch/arm/dts/tegra20-u-boot.dtsi

>> I'd expect to see more "U-Boot overlay" DTs than this; I recall there being more differences between U-Boot and kernel DTS files when I last sync'd the two.
>
> Yes but most of those changes should be dropped. I did a partial sync
> a few months back but if you recall there were still differences. Is
> this something the Tegra maintainer might look at?
>
> I don't want to immortalise those differences in a separate U-Boot
> file when really we should just get rid of them.

 From my perspective, we should have two files:

1) The base DT.

This should not contain any U-Boot modifications, and should exactly 
match the DT used elsewhere, such as in mainline Linux. Since this 
should always match other DTs, we should pretty much always be able to 
over-write it with any updated DT from other sources.

2) The U-Boot modifications.

This always contain /all/ local modifications applied by U-Boot. It 
shouldn't matter why the change was made, or how long we hope/expect the 
delta to continue to exist. This will isolate all U-Boot changes into 
this file so it's obvious what local changes exist. If some changes are 
intended to be temporary, we can add a comment to that effect, and 
eventually submit a patch to remove the delta.

I don't think that putting a change into this "U-Boot local overlay" 
should in any way imply that the change is by definition correct and 
long-term; some changes may satisfy that decription and others won't. 
Just like we sometimes have C code that we wish we didn't and eventually 
clean up.