linux-kernel - Re: [PATCH v2 4/7] arm64: dts: allwinner: h6: Add GPU Operating Performance Points table

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Date:   Mon, 6 Apr 2020 10:58:44 +0200
From:   Clément Péron <peron.clem@...il.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH v2 4/7] arm64: dts: allwinner: h6: Add GPU Operating
 Performance Points table

Hi Maxime,

On Mon, 6 Apr 2020 at 10:16, Maxime Ripard <maxime@...no.tech> wrote:
>
> On Sun, Apr 05, 2020 at 07:35:58PM +0200, Clément Péron wrote:
> > Add an Operating Performance Points table for the GPU to
> > enable Dynamic Voltage & Frequency Scaling on the H6.
> >
> > Signed-off-by: Clément Péron <peron.clem@...il.com>
> > ---
> >  .../boot/dts/allwinner/sun50i-h6-gpu-opp.dtsi | 74 +++++++++++++++++++
> >  1 file changed, 74 insertions(+)
> >  create mode 100644 arch/arm64/boot/dts/allwinner/sun50i-h6-gpu-opp.dtsi
> >
> > diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6-gpu-opp.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-h6-gpu-opp.dtsi
> > new file mode 100644
> > index 000000000000..4a1814844fe0
> > --- /dev/null
> > +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6-gpu-opp.dtsi
> > @@ -0,0 +1,74 @@
> > +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
> > +// Copyright (C) 2020 Clément Péron <peron.clem@...il.com>
> > +
> > +/ {
> > +     gpu_opp_table: opp_table1 {
>
> A node name is supposed to be a generic description, so what about
> using gpu-opp-table (and cpu-opp-table) instead?
>
> > +             compatible = "operating-points-v2";
> > +
> > +             opp@...000000 {
> > +                     opp-hz = /bits/ 64 <756000000>;
> > +                     opp-microvolt = <1040000>;
> > +             };
> > +             opp@...000000 {
> > +                     opp-hz = /bits/ 64 <624000000>;
> > +                     opp-microvolt = <950000>;
> > +             };
>
> Ordering by ascending frequency would be great here.
Indeed will fix it.

>
> Also, why did you need to create a new DTSI for it? Is there some
> downside to enabling it for all the users?

I didn't want to enable it for all boards as I can't test them and not all board
have a dedicated regulator for VDD-GPU.
Hence my question in the cover,
But with Jernej Škrabec test on Tanix TX6 I think it can be safely
enable on all boards.

Regards,
Clement

>
> Maxime