On Wed, 2019-07-24 at 21:24 +0200, Krzysztof Kozlowski wrote:
> On Tue, Jul 23, 2019 at 02:20:13PM +0200, Artur Świgoń wrote:
> > This patch adds two fields tp the Exynos4412 DTS:
>
> tp->to
Fixed. Thanks for catching the typo :)
> > - parent: to declare connections between nodes that are not in a
> > parent-child relation in devfreq;
>
> Is it a standard property?
> The explanation needs some improvement... why are you adding parent to a
> devices which are not child-parent?
This is not a standard property. I actually wanted to call it 'neighbor' at first. If you take a look at [1] and search for 'Exynos4x12', you will see that there are two power lines, and each has exactly one parent block (the rest are modelled in devfreq as its children). In [2], the parent of each child is indicated using the 'devfreq' property, e.g.,
&bus_display {
devfreq = <&bus_leftbus>;
status = "okay";
};
The single piece missing to make this topology a connected graph (for
interconnect QoS purposes) is the 'parent' property I proposed in this patch.
bus_leftbus is dependent on bus_dmc, therefore using the term 'parent' is
justified IMHO.
The explanation could be improved by adding what Chanwoo Choi <
cw00.choi@xxxxxxxxxxx> expressed in a parallel reply to this patch:
> - If 'devfreq' property is used between buses,
> it indicates that there are requirement of sharing of power line.
> - If 'parent' property is used between buses,
> it indicates that there are requirement of interconnect connection.
[1] Documentation/devicetree/bindings/devfreq/exynos-bus.txt
[2] arch/arm/boot/dts/exynos4412-odroid-common.dtsi (subject of this patch)
Best regards,
--
Artur Świgoń
Samsung R&D Institute Poland
Samsung Electronics
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