Hi Rob,

On Tue, Feb 28, 2017 at 4:52 PM, Rob Herring [off-list ref] wrote:

On Tue, Feb 28, 2017 at 9:14 AM, Ulf Hansson [off-list ref] wrote:

quoted

[...]

quoted

quoted

                                    ---> Parent domain-2 (Contains Perfomance states)
                                    |
                                    |
C.) DeviceX  --->  Parent-domain-1  |
                                    |
                                    |
                                    ---> Parent domain-3 (Contains Perfomance states)

I'm a bit confused. How does a domain have 2 parent domains?

This comes from the early design of the generic PM domain, thus I
assume we have some HW with such complex PM topology. However, I don't
know if it is actually being used.

Moreover, the corresponding DT bindings for "power-domains" parents,
can easily be extended to cover more than one parent. See more in
Documentation/devicetree/bindings/power/power_domain.txt

I could easily see device having 2 power domains. For example a cpu
may have separate domains for RAM/caches and logic. And nesting of
power domains is certainly common, but a power domain being contained
in 2 different parents? I don't even see how that is possible in the
physical design. Now if we're mixing PM and power domains again and
the cpu device is pointing to the cpu PM domain which contains 2 power
domains, then certainly that is possible.

One of them could be a power area, the other a clock domain.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds