Re: PMU node location

[Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 01/12/2013 09:10 PM, Stephen Warren wrote:
> On 01/12/2013 08:54 AM, Rob Herring wrote:
>> On 01/10/2013 07:47 AM, Michal Simek wrote:
>>> Hi Rob, Mark, Grant and others,
>>>
>>> I want to check with you the location of ARM pmu node
>>> I see that
>>> 1) highbank and dbx5x0 have it in soc node
>>>
>>> 2) vexpress and tegra have no main bus and pmu is in root like all
>>> others devices.
>>> (Any reason no to have main bus? Does it mean that there is no bus or
>>> that all
>>> devices are accessible?)
>>
>> That seems really wrong in general. Any memory mapped device is on a bus
>> of some kind. I'm not sure the reasoning. Perhaps Stephen can explain.
> 
> I saw no need to have add a bus node (there wasn't one before I started
> touching DT on Tegra); the top-level of the DT represents the CPU's
> entire view of the address space and has #address-cells/#size-cells, so
> devices get probed there just fine, whether they're addressed MMIO
> devices or not.

The top level doesn't really represent a bus. It is basically all the
things that have no hierarchical relationship (cpu, memory, chosen,
peripheral buses). The reason to have a bus node is to define "simple-bus"

While I would do it differently, I don't recommend changing it at this
point. Although, this could be changed without compatibility issues.

Rob