linux-kernel - Re: [RFC PATCH v3 4/7] arm: dts: exynos: Add interconnect bindings for Exynos4412

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Date:   Tue, 31 Dec 2019 08:18:01 +0100
From:   Artur Świgoń <a.swigon@...sung.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        cw00.choi@...sung.com, myungjoo.ham@...sung.com,
        inki.dae@...sung.com, sw0312.kim@...sung.com,
        georgi.djakov@...aro.org, leonard.crestez@....com,
        m.szyprowski@...sung.com, b.zolnierkie@...sung.com
Subject: Re: [RFC PATCH v3 4/7] arm: dts: exynos: Add interconnect bindings
 for Exynos4412

Hi,

On Mon, 2019-12-30 at 16:44 +0100, Krzysztof Kozlowski wrote:
> On Fri, Dec 20, 2019 at 12:56:50PM +0100, Artur Świgoń wrote:
> > This patch adds the following properties to the Exynos4412 DT:
> >   - exynos,interconnect-parent-node: to declare connections between
> >     nodes in order to guarantee PM QoS requirements between nodes;
> >   - #interconnect-cells: required by the interconnect framework.
> > 
> > Note that #interconnect-cells is always zero and node IDs are not
> > hardcoded anywhere.
> > 
> > Signed-off-by: Artur Świgoń <a.swigon@...sung.com>
> > ---
> >  arch/arm/boot/dts/exynos4412-odroid-common.dtsi | 5 +++++
> >  1 file changed, 5 insertions(+)
> 
> The order of patches is confusing. Patches 4 and 6 are split - do the
> depend on 5? I doubt but...

Let me elaborate:

The order of the patches in this series is such that every subsequent
patch adds some functionality (and, of course, applying patches one-by-one
yields a working kernel at every step). Specifically for patches 04--07:

 -- patch 04 adds interconnect _provider_ properties for Exynos4412;
 -- patch 05 implements interconnect provider logic (depends on patch 04);
 -- patch 06 adds interconnect _consumer_ properties for Exynos4412 mixer;
 -- patch 07 implements interconnect consumer logic (depends on patches
    05 & 06);

My reasoning is that this order allows to e.g., merge the interconnect
provider for exynos-bus and leave the consumers for later (not limited to
the mixer). I hope this makes sense.

> Adjust the title to match the contents - you are not adding bindings but
> properties to bus nodes. Also the prefix is ARM: (look at recent
> commits).

OK.

> > 
> > diff --git a/arch/arm/boot/dts/exynos4412-odroid-common.dtsi b/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
> > index 4ce3d77a6704..d9d70eacfcaf 100644
> > --- a/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
> > +++ b/arch/arm/boot/dts/exynos4412-odroid-common.dtsi
> > @@ -90,6 +90,7 @@
> >  &bus_dmc {
> >  	exynos,ppmu-device = <&ppmu_dmc0_3>, <&ppmu_dmc1_3>;
> >  	vdd-supply = <&buck1_reg>;
> > +	#interconnect-cells = <0>;
> 
> This does not look like property of Odroid but Exynos4412 or Exynos4.

Strangely enough, this file is where the 'exynos,parent-bus' (aka. 'devfreq')
properties are located (and everything in this RFC concerns devfreq).

Regards,
-- 
Artur Świgoń
Samsung R&D Institute Poland
Samsung Electronics