Hello,

On 2014-11-25 10:19, Geert Uytterhoeven wrote:

On Tue, Nov 25, 2014 at 9:57 AM, amit daniel kachhap
[off-list ref]  wrote:

quoted

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diff --git a/Documentation/devicetree/bindings/arm/exynos/power_domain.txt b/Documentation/devicetree/bindings/arm/exynos/power_domain.txt
index 00ebda1..0160bdc 100644
--- a/Documentation/devicetree/bindings/arm/exynos/power_domain.txt
+++ b/Documentation/devicetree/bindings/arm/exynos/power_domain.txt

@@ -24,6 +24,7 @@ Optional Properties:
         - pclkN, clkN: Pairs of parent of input clock and input clock to the
                 devices in this power domain. Maximum of 4 pairs (N = 0 to 3)
                 are supported currently.
+- parents: phandle of parent power domains.

Why not using just "power-domains = <&pd_top>"?
This is consistent with how clocks refer to their parent clocks.

I agree. The only question is weather exynos dts should keep using 
samsung,power-domain
property, or switch to generic 'power-domains' approach. I assume that 
exynos-pm driver
should support both.

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  Node of a device using power domains must have a samsung,power-domain property
  defined with a phandle to respective power domain.

@@ -48,6 +49,7 @@ Example:
         mfc_pd: power-domain at 10044060 {
                 compatible = "samsung,exynos4210-pd", "samsung,exynos7-pd-mfc";
                 reg = <0x10044060 0x20>;
+               parents = <&pd_top>;
                 #power-domain-cells = <0>;
         };

This seems like a good and generic approach to describe that a PM
domain could have a parent. I would suggest to rename it, such it
reflects its a PM domain binding though.

I am not sure if this is generic. I guess PD's represented like below
are more generic.
PD1 {
         PD2 {
                 PD3 {
                 };
         };
};

Such a representation is not always possible.
If you have one power-controller for a hierarchy of PM domains, you can
use it.
If you have multiple power-controllers, the power controller nodes are at the
same level in DT, so you'll have to use "power-domains" properties to link
them together.

I agree. I will send updated patch for this purpose for existing exynos4 
power domain driver.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland