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

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Message-ID: <20190214143842.nqsh6trwdjxq2ecd@flea>
Date:   Thu, 14 Feb 2019 15:38:42 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Yangtao Li <tiny.windzz@...il.com>
Cc:     wens@...e.org, robh+dt@...nel.org, mark.rutland@....com,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] arm64: dts: allwinner: h6: Add CPU Operating
 Performance Points table

Hi,

On Thu, Feb 14, 2019 at 08:09:10AM -0500, Yangtao Li wrote:
> Add an OPP (Operating Performance Points) table for the CPU cores to
> enable DVFS (Dynamic Voltage & Frequency Scaling) on the H6. This
> information comes from github.
> 
> Signed-off-by: Yangtao Li <tiny.windzz@...il.com>
> ---
>  arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi | 61 ++++++++++++++++++++
>  1 file changed, 61 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> index 57a1390ecdc2..46a4a69eb38f 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> @@ -28,6 +28,8 @@
>  			enable-method = "psci";
>  			clocks = <&ccu CLK_CPUX>; 
>  			clock-latency-ns = <244144>; /* 8 32k periods */
> +			operating-points-v2 = <&cpu_opp_table>;
> +			#cooling-cells = <2>;
>  		};
>  
>  		cpu1: cpu@1 {
> @@ -37,6 +39,8 @@
>  			enable-method = "psci";
>  			clocks = <&ccu CLK_CPUX>; 
>  			clock-latency-ns = <244144>; /* 8 32k periods */
> +			operating-points-v2 = <&cpu_opp_table>;
> +			#cooling-cells = <2>;
>  		};
>  
>  		cpu2: cpu@2 {
> @@ -46,6 +50,8 @@
>  			enable-method = "psci";
>  			clocks = <&ccu CLK_CPUX>; 
>  			clock-latency-ns = <244144>; /* 8 32k periods */
> +			operating-points-v2 = <&cpu_opp_table>;
> +			#cooling-cells = <2>;
>  		};
>  
>  		cpu3: cpu@3 {
> @@ -55,6 +61,61 @@
>  			enable-method = "psci";
>  			clocks = <&ccu CLK_CPUX>; 
>  			clock-latency-ns = <244144>; /* 8 32k periods */
> +			operating-points-v2 = <&cpu_opp_table>;
> +			#cooling-cells = <2>;
> +		};
> +	};
> +
> +	cpu_opp_table: opp_table {
> +		compatible = "operating-points-v2";
> +		opp-shared;
> +
> +		opp@...000000 {
> +			opp-hz = /bits/ 64 <480000000>;
> +			opp-microvolt = <800000 800000 880000>;
> +			clock-latency-ns = <244144>; /* 8 32k periods */
> +		};
> +
> +		opp@...000000 {
> +			opp-hz = /bits/ 64 <720000000>;
> +			opp-microvolt = <800000 800000 880000>;
> +			clock-latency-ns = <244144>; /* 8 32k periods */
> +		};
> +
> +		opp@...000000 {
> +			opp-hz = /bits/ 64 <816000000>;
> +			opp-microvolt = <800000 800000 880000>;
> +			clock-latency-ns = <244144>; /* 8 32k periods */
> +		};
> +
> +		opp@...000000 {
> +			opp-hz = /bits/ 64 <888000000>;
> +			opp-microvolt = <800000 800000 940000>;
> +			clock-latency-ns = <244144>; /* 8 32k periods */
> +		};
> +
> +		opp@...0000000 {
> +			opp-hz = /bits/ 64 <1080000000>;
> +			opp-microvolt = <840000 840000 1060000>;
> +			clock-latency-ns = <244144>; /* 8 32k periods */
> +		};
> +
> +		opp@...0000000 {
> +			opp-hz = /bits/ 64 <1320000000>;
> +			opp-microvolt = <900000 900000 1160000>;
> +			clock-latency-ns = <244144>; /* 8 32k periods */
> +		};
> +
> +		opp@...8000000 {
> +			opp-hz = /bits/ 64 <1488000000>;
> +			opp-microvolt = <960000 960000 1160000>;
> +			clock-latency-ns = <244144>; /* 8 32k periods */
> +		};
> +
> +		opp@...0000000 {
> +			opp-hz = /bits/ 64 <1800000000>;
> +			opp-microvolt = <1060000 1060000 1160000>;
> +			clock-latency-ns = <244144>; /* 8 32k periods */

So we definitely want to have that tested, especially since cpufreq
can lead to all kind of hard to debug errors (brown-outs, CPU lockups,
cache corruption, etc.). I good way to test that would be to use
cpufreq-ljt-stress-test here:
https://github.com/ssvb/cpuburn-arm/blob/master/cpufreq-ljt-stress-test

I'm especially worried about the higher frequencies that will probably
make the SoC heat too much

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com