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Date: Tue, 30 Apr 2024 00:10:02 +0100
From: Andre Przywara <andre.przywara@arm.com>
To: Dragan Simic <dsimic@manjaro.org>
Cc: linux-sunxi@lists.linux.dev, wens@csie.org, jernej.skrabec@gmail.com,
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 conor+dt@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: dts: allwinner: Add cache information to the SoC
 dtsi for H6
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On Sun, 28 Apr 2024 13:40:36 +0200
Dragan Simic <dsimic@manjaro.org> wrote:

> Add missing cache information to the Allwinner H6 SoC dtsi, to allow
> the userspace, which includes lscpu(1) that uses the virtual files provided
> by the kernel under the /sys/devices/system/cpu directory, to display the
> proper H6 cache information.
> 
> Adding the cache information to the H6 SoC dtsi also makes the following
> warning message in the kernel log go away:
> 
>   cacheinfo: Unable to detect cache hierarchy for CPU 0
> 
> The cache parameters for the H6 dtsi were obtained and partially derived
> by hand from the cache size and layout specifications found in the following
> datasheets and technical reference manuals:
> 
>   - Allwinner H6 V200 datasheet, version 1.1
>   - ARM Cortex-A53 revision r0p3 TRM, version E
> 
> For future reference, here's a brief summary of the documentation:
> 
>   - All caches employ the 64-byte cache line length
>   - Each Cortex-A53 core has 32 KB of L1 2-way, set-associative instruction
>     cache and 32 KB of L1 4-way, set-associative data cache
>   - The entire SoC has 512 KB of unified L2 16-way, set-associative cache
> 
> Signed-off-by: Dragan Simic <dsimic@manjaro.org>

I can confirm that the data below matches the manuals, but also the
decoding of the architectural cache type registers (CCSIDR_EL1):
  L1D: 32 KB: 128 sets, 4 way associative, 64 bytes/line
  L1I: 32 KB: 256 sets, 2 way associative, 64 bytes/line
  L2: 512 KB: 512 sets, 16 way associative, 64 bytes/line

tinymembench results for the H6 are available here:
https://github.com/ThomasKaiser/sbc-bench/blob/master/results/26Ph.txt
and confirm the theory. Also ran it locally with similar results.

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Thanks,
Andre

> ---
>  arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi | 37 ++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> index d11e5041bae9..1a63066396e8 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> @@ -29,36 +29,73 @@ cpu0: cpu@0 {
>  			clocks = <&ccu CLK_CPUX>;
>  			clock-latency-ns = <244144>; /* 8 32k periods */
>  			#cooling-cells = <2>;
> +			i-cache-size = <0x8000>;
> +			i-cache-line-size = <64>;
> +			i-cache-sets = <256>;
> +			d-cache-size = <0x8000>;
> +			d-cache-line-size = <64>;
> +			d-cache-sets = <128>;
> +			next-level-cache = <&l2_cache>;
>  		};
>  
>  		cpu1: cpu@1 {
>  			compatible = "arm,cortex-a53";
>  			device_type = "cpu";
>  			reg = <1>;
>  			enable-method = "psci";
>  			clocks = <&ccu CLK_CPUX>;
>  			clock-latency-ns = <244144>; /* 8 32k periods */
>  			#cooling-cells = <2>;
> +			i-cache-size = <0x8000>;
> +			i-cache-line-size = <64>;
> +			i-cache-sets = <256>;
> +			d-cache-size = <0x8000>;
> +			d-cache-line-size = <64>;
> +			d-cache-sets = <128>;
> +			next-level-cache = <&l2_cache>;
>  		};
>  
>  		cpu2: cpu@2 {
>  			compatible = "arm,cortex-a53";
>  			device_type = "cpu";
>  			reg = <2>;
>  			enable-method = "psci";
>  			clocks = <&ccu CLK_CPUX>;
>  			clock-latency-ns = <244144>; /* 8 32k periods */
>  			#cooling-cells = <2>;
> +			i-cache-size = <0x8000>;
> +			i-cache-line-size = <64>;
> +			i-cache-sets = <256>;
> +			d-cache-size = <0x8000>;
> +			d-cache-line-size = <64>;
> +			d-cache-sets = <128>;
> +			next-level-cache = <&l2_cache>;
>  		};
>  
>  		cpu3: cpu@3 {
>  			compatible = "arm,cortex-a53";
>  			device_type = "cpu";
>  			reg = <3>;
>  			enable-method = "psci";
>  			clocks = <&ccu CLK_CPUX>;
>  			clock-latency-ns = <244144>; /* 8 32k periods */
>  			#cooling-cells = <2>;
> +			i-cache-size = <0x8000>;
> +			i-cache-line-size = <64>;
> +			i-cache-sets = <256>;
> +			d-cache-size = <0x8000>;
> +			d-cache-line-size = <64>;
> +			d-cache-sets = <128>;
> +			next-level-cache = <&l2_cache>;
> +		};
> +
> +		l2_cache: l2-cache {
> +			compatible = "cache";
> +			cache-level = <2>;
> +			cache-unified;
> +			cache-size = <0x80000>;
> +			cache-line-size = <64>;
> +			cache-sets = <512>;
>  		};
>  	};
>  
>