linux-kernel - Re: [PATCH 1/2] arm64: dts: rk3328: add gpu opp table

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Date:   Sun, 17 Oct 2021 11:29:41 -0400
From:   Trevor Woerner <twoerner@...il.com>
To:     Johan Jonker <jbx6244@...il.com>
Cc:     linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>, Chen-Yu Tsai <wens@...e.org>,
        David Wu <david.wu@...k-chips.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Cameron Nemo <cnemo@...anota.com>,
        Robin Murphy <robin.murphy@....com>,
        Elaine Zhang <zhangqing@...k-chips.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:ARM/Rockchip SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Rockchip SoC support" 
        <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH 1/2] arm64: dts: rk3328: add gpu opp table

On Sat 2021-10-16 @ 10:45:04 PM, Johan Jonker wrote:
> On 10/16/21 5:45 PM, Trevor Woerner wrote:
> > Add an operating-points table and cooling entry to the GPU on the
> > RK3328 SoC to improve its performance. According to its datasheet[1]
> > the maximum frequency of the Mali-450 MP2 GPU found on the RK3328 SoC
> > is 500MHz.
> > 
> > On my rock64 device, under x11, glmark2-es2 performance increased from
> > around 60 to just over 100. Same device running glmark2-es2 under
> > wayland/weston improved from just over 100 to just over 200.
> > 
> > [1] https://rockchip.fr/RK3328%20datasheet%20V1.2.pdf
> > 
> > Signed-off-by: Trevor Woerner <twoerner@...il.com>
> > ---
> >  arch/arm64/boot/dts/rockchip/rk3328.dtsi | 26 +++++++++++++++++++++++-
> >  1 file changed, 25 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/boot/dts/rockchip/rk3328.dtsi b/arch/arm64/boot/dts/rockchip/rk3328.dtsi
> > index 8c821acb21ff..5e1dcf71e414 100644
> > --- a/arch/arm64/boot/dts/rockchip/rk3328.dtsi
> > +++ b/arch/arm64/boot/dts/rockchip/rk3328.dtsi
> > @@ -532,7 +532,8 @@ map0 {
> >  					cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> >  							 <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> >  							 <&cpu2 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > -							 <&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> > +							 <&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > +							 <&gpu THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> >  					contribution = <4096>;
> >  				};
> >  			};
> > @@ -617,6 +618,29 @@ gpu: gpu@...00000 {
> >  		clocks = <&cru ACLK_GPU>, <&cru ACLK_GPU>;
> >  		clock-names = "bus", "core";
> >  		resets = <&cru SRST_GPU_A>;
> > +		operating-points-v2 = <&gpu_opp_table>;
> > +		#cooling-cells = <2>;
> > +	};
> > +
> 
> > +	gpu_opp_table: gpu-opp-table {
> 
> After the conversion to YAML of the Operating Performance Points(OPP)
> binding the operating-points-v2 property expects the nodename to have
> the '^opp-table(-[a-z0-9]+)?$' format.
> 
> make ARCH=arm64 dtbs_check
> DT_SCHEMA_FILES=Documentation/devicetree/bindings/opp/opp-v2.yaml

Thanks, I wasn't aware.

> > +		compatible = "operating-points-v2";
> > +
> > +		opp-200000000 {
> > +			opp-hz = /bits/ 64 <200000000>;
> > +			opp-microvolt = <1100000>;
> > +		};
> > +		opp-300000000 {
> > +			opp-hz = /bits/ 64 <300000000>;
> > +			opp-microvolt = <1100000>;
> > +		};
> > +		opp-400000000 {
> > +			opp-hz = /bits/ 64 <400000000>;
> > +			opp-microvolt = <1100000>;
> > +		};
> > +		opp-500000000 {
> > +			opp-hz = /bits/ 64 <500000000>;
> > +			opp-microvolt = <1100000>;
> > +		};
> >  	};
> 
> opp-microvolt has the same value for every node vs. table below?

On page 1 of the schematic for the rock64
https://files.pine64.org/doc/rock64/ROCK64_Schematic_v3.0_20181105.pdf is a
table ("Power Timing") showing BUCK1 at 1.1V. I interpreted this to mean that
VDD_LOG should always be at 1.1V, regardless of frequency.

> See also previous discussion:
> 
> https://lore.kernel.org/linux-rockchip/3c95c29b-6c07-5945-ac22-d683997e1ca0@arm.com/
> 
> Is that now fixed/checked?

I wasn't aware of the previous/on-going discussion regarding a gpu opp table
for this SoC. Perhaps that explains my suspicions? I couldn't help wonder why
the frequency is always reported as 163840000 even when I have an opp table
that only has the 500MHz entry?

I'll investigate whether I can prove or disprove the scaling is actually
occurring?

Best regards,
	Trevor