linux-kernel - Re: [PATCH v4 3/5] arm64: dts: allwinner: h6: Add GPU OPP table

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Date:   Tue, 6 Sep 2022 21:26:34 +0200
From:   Clément Péron <peron.clem@...il.com>
To:     Jernej Škrabec <jernej.skrabec@...il.com>
Cc:     Chen-Yu Tsai <wens@...e.org>, Samuel Holland <samuel@...lland.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-sunxi@...ts.linux.dev,
        linux-kernel <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v4 3/5] arm64: dts: allwinner: h6: Add GPU OPP table

Hi Jernej,

On Tue, 6 Sept 2022 at 21:10, Jernej Škrabec <jernej.skrabec@...il.com> wrote:
>
> Dne torek, 06. september 2022 ob 17:30:32 CEST je Clément Péron napisal(a):
> > Add an Operating Performance Points table for the GPU to
> > enable Dynamic Voltage & Frequency Scaling on the H6.
> >
> > The voltage range is set with minimal voltage set to the target
> > and the maximal voltage set to 1.2V. This allow DVFS framework to
> > work properly on board with fixed regulator.
> >
> > Signed-off-by: Clément Péron <peron.clem@...il.com>
> > ---
> >  .../boot/dts/allwinner/sun50i-h6-gpu-opp.dtsi | 87 +++++++++++++++++++
> >  1 file changed, 87 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..b48049c4fc85
> > --- /dev/null
> > +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6-gpu-opp.dtsi
> > @@ -0,0 +1,87 @@
> > +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
> > +// Copyright (C) 2022 Clément Péron <peron.clem@...il.com>
> > +
> > +/ {
> > +     gpu_opp_table: opp-table-gpu {
> > +             compatible = "operating-points-v2";
> > +
> > +             opp-216000000 {
> > +                     opp-hz = /bits/ 64 <216000000>;
> > +                     opp-microvolt = <810000 810000 1200000>;
> > +             };
> > +
> > +             opp-264000000 {
> > +                     opp-hz = /bits/ 64 <264000000>;
> > +                     opp-microvolt = <810000 810000 1200000>;
> > +             };
>
> As mentioned in clock patch review, rates below 288 MHz are deemed unstable on
> GPU PLL by vendor GPU kernel driver. At least in the BSP version that I have.
> Did you test these points? If not, better to drop them.

I changed the governor to userspace and set the freq to 216MHz / 264MHz
Run glmark2 and didn't observe any glitch nor issue.

I'm not sure if it's enough to say it's stable but I didn't observe
any strange behavior.

Regards,
Clement

>
> Best regards,
> Jernej
>
> > +
> > +             opp-312000000 {
> > +                     opp-hz = /bits/ 64 <312000000>;
> > +                     opp-microvolt = <810000 810000 1200000>;
> > +             };
> > +
> > +             opp-336000000 {
> > +                     opp-hz = /bits/ 64 <336000000>;
> > +                     opp-microvolt = <810000 810000 1200000>;
> > +             };
> > +
> > +             opp-360000000 {
> > +                     opp-hz = /bits/ 64 <360000000>;
> > +                     opp-microvolt = <820000 820000 1200000>;
> > +             };
> > +
> > +             opp-384000000 {
> > +                     opp-hz = /bits/ 64 <384000000>;
> > +                     opp-microvolt = <830000 830000 1200000>;
> > +             };
> > +
> > +             opp-408000000 {
> > +                     opp-hz = /bits/ 64 <408000000>;
> > +                     opp-microvolt = <840000 840000 1200000>;
> > +             };
> > +
> > +             opp-420000000 {
> > +                     opp-hz = /bits/ 64 <420000000>;
> > +                     opp-microvolt = <850000 850000 1200000>;
> > +             };
> > +
> > +             opp-432000000 {
> > +                     opp-hz = /bits/ 64 <432000000>;
> > +                     opp-microvolt = <860000 860000 1200000>;
> > +             };
> > +
> > +             opp-456000000 {
> > +                     opp-hz = /bits/ 64 <456000000>;
> > +                     opp-microvolt = <870000 870000 1200000>;
> > +             };
> > +
> > +             opp-504000000 {
> > +                     opp-hz = /bits/ 64 <504000000>;
> > +                     opp-microvolt = <890000 890000 1200000>;
> > +             };
> > +
> > +             opp-540000000 {
> > +                     opp-hz = /bits/ 64 <540000000>;
> > +                     opp-microvolt = <910000 910000 1200000>;
> > +             };
> > +
> > +             opp-576000000 {
> > +                     opp-hz = /bits/ 64 <576000000>;
> > +                     opp-microvolt = <930000 930000 1200000>;
> > +             };
> > +
> > +             opp-624000000 {
> > +                     opp-hz = /bits/ 64 <624000000>;
> > +                     opp-microvolt = <950000 950000 1200000>;
> > +             };
> > +
> > +             opp-756000000 {
> > +                     opp-hz = /bits/ 64 <756000000>;
> > +                     opp-microvolt = <1040000 1040000 1200000>;
> > +             };
> > +     };
> > +};
> > +
> > +&gpu {
> > +     operating-points-v2 = <&gpu_opp_table>;
> > +};
> > --
> > 2.34.1
>
>