linux-kernel - Re: [PATCH v2 01/11] arm64: dts: amlogic: Add cache information to the Amlogic GXBB and GXL SoC

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Message-Id: <19AB5D06-DEB6-4C38-B90D-FCDD9719312C@hewittfamily.org.uk>
Date: Mon, 25 Aug 2025 11:58:48 +0400
From: Christian Hewitt <christian@...ittfamily.org.uk>
To: Anand Moon <linux.amoon@...il.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>,
 Kevin Hilman <khilman@...libre.com>,
 Jerome Brunet <jbrunet@...libre.com>,
 Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 "moderated list:ARM/Amlogic Meson SoC support" <linux-arm-kernel@...ts.infradead.org>,
 "open list:ARM/Amlogic Meson SoC support" <linux-amlogic@...ts.infradead.org>,
 "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 01/11] arm64: dts: amlogic: Add cache information to
 the Amlogic GXBB and GXL SoC

> On 25 Aug 2025, at 10:51 am, Anand Moon <linux.amoon@...il.com> wrote:
> 
> As per S905 and S905X datasheet add missing cache information to
> the Amlogic GXBB and GXL SoC.
> 
> - Each Cortex-A53 core has 32KB of L1 instruction cache available and
> 32KB of L1 data cache available.
> - Along with 512KB Unified L2 cache.
> 
> Cache memory significantly reduces the time it takes for the CPU
> to access data and instructions, leading to faster program execution
> and overall system responsiveness.

Hello Anand,

I’m wondering if we are “enabling caching” in these patches (could be
a significant gain, as per text) or we are “optimising caching” meaning
the kernel currently assumes generic/safe defaults so having accurate
descriptions in dt allows better efficiency (marginal gain)?

Stats are also subjective to the workload used, but do you have any
kind of before/after benchmarks? (for any of the SoCs in the patchset)

Christian

> Signed-off-by: Anand Moon <linux.amoon@...il.com>
> ---
> arch/arm64/boot/dts/amlogic/meson-gx.dtsi | 27 +++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/amlogic/meson-gx.dtsi b/arch/arm64/boot/dts/amlogic/meson-gx.dtsi
> index 7d99ca44e660..c1d8e81d95cb 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-gx.dtsi
> +++ b/arch/arm64/boot/dts/amlogic/meson-gx.dtsi
> @@ -95,6 +95,12 @@ cpu0: cpu@0 {
> compatible = "arm,cortex-a53";
> reg = <0x0 0x0>;
> enable-method = "psci";
> + d-cache-line-size = <32>;
> + d-cache-size = <0x8000>;
> + d-cache-sets = <32>;
> + i-cache-line-size = <32>;
> + i-cache-size = <0x8000>;
> + i-cache-sets = <32>;
> next-level-cache = <&l2>;
> clocks = <&scpi_dvfs 0>;
> #cooling-cells = <2>;
> @@ -105,6 +111,12 @@ cpu1: cpu@1 {
> compatible = "arm,cortex-a53";
> reg = <0x0 0x1>;
> enable-method = "psci";
> + d-cache-line-size = <32>;
> + d-cache-size = <0x8000>;
> + d-cache-sets = <32>;
> + i-cache-line-size = <32>;
> + i-cache-size = <0x8000>;
> + i-cache-sets = <32>;
> next-level-cache = <&l2>;
> clocks = <&scpi_dvfs 0>;
> #cooling-cells = <2>;
> @@ -115,6 +127,12 @@ cpu2: cpu@2 {
> compatible = "arm,cortex-a53";
> reg = <0x0 0x2>;
> enable-method = "psci";
> + d-cache-line-size = <32>;
> + d-cache-size = <0x8000>;
> + d-cache-sets = <32>;
> + i-cache-line-size = <32>;
> + i-cache-size = <0x8000>;
> + i-cache-sets = <32>;
> next-level-cache = <&l2>;
> clocks = <&scpi_dvfs 0>;
> #cooling-cells = <2>;
> @@ -125,6 +143,12 @@ cpu3: cpu@3 {
> compatible = "arm,cortex-a53";
> reg = <0x0 0x3>;
> enable-method = "psci";
> + d-cache-line-size = <32>;
> + d-cache-size = <0x8000>;
> + d-cache-sets = <32>;
> + i-cache-line-size = <32>;
> + i-cache-size = <0x8000>;
> + i-cache-sets = <32>;
> next-level-cache = <&l2>;
> clocks = <&scpi_dvfs 0>;
> #cooling-cells = <2>;
> @@ -134,6 +158,9 @@ l2: l2-cache0 {
> compatible = "cache";
> cache-level = <2>;
> cache-unified;
> + cache-size = <0x80000>; /* L2. 512 KB */
> + cache-line-size = <64>;
> + cache-sets = <512>;
> };
> };
> 
> -- 
> 2.50.1
> 
> 
> _______________________________________________
> linux-amlogic mailing list
> linux-amlogic@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-amlogic

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