linux-kernel - Re: [PATCH v3 3/3] arm64: dts: ti: k3-am62l: support cpufreq

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Message-ID: <652d6b5a-57cc-4985-87fb-94eb53c520be@ti.com>
Date: Wed, 21 Jan 2026 10:27:15 -0600
From: Kendall Willis <k-willis@...com>
To: Dhruva Gole <d-gole@...com>, "Rafael J. Wysocki" <rafael@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>, Nishanth Menon <nm@...com>, "Vignesh
 Raghavendra" <vigneshr@...com>, Tero Kristo <kristo@...nel.org>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>
CC: Sebin Francis <sebin.francis@...com>, Bryan Brattlof <bb@...com>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] arm64: dts: ti: k3-am62l: support cpufreq

On 1/20/26 05:47, Dhruva Gole wrote:
> Enable CPUFreq support for AM62L SoC by adding the relevant OPP efuse table
> syscon to k3-am62l-wakeup.dtsi for speed grade detection.
> 
> Add the operating-points-v2 table with CPU frequency steps from 200MHz to
> 1.25GHz to k3-am62l3.dtsi
> 
> Configure CPU clocks to reference the SCMI clock controller for frequency
> scaling
> 
> This enables proper CPU frequency scaling capabilities for the AM62L SoC
> using the ARM SCMI protocol to interact with the power management firmware.
> 
> Signed-off-by: Dhruva Gole <d-gole@...com>
> ---
>   arch/arm64/boot/dts/ti/k3-am62l-wakeup.dtsi |  5 +++
>   arch/arm64/boot/dts/ti/k3-am62l3.dtsi       | 47 +++++++++++++++++++++++++++++
>   2 files changed, 52 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/ti/k3-am62l-wakeup.dtsi b/arch/arm64/boot/dts/ti/k3-am62l-wakeup.dtsi
> index 61bfcdcfc66ea8d802a36ed43cd01fbbf3decc70..a42ccd0d2fcc4d204cae81508f839c44ce83f558 100644
> --- a/arch/arm64/boot/dts/ti/k3-am62l-wakeup.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-am62l-wakeup.dtsi
> @@ -127,6 +127,11 @@ chipid: chipid@14 {
>   			bootph-all;
>   		};
>   
> +		opp_efuse_table: syscon@18 {
> +			compatible = "ti,am62-opp-efuse-table", "syscon";
> +			reg = <0x18 0x4>;
> +		};
> +
>   		cpsw_mac_syscon: ethernet-mac-syscon@...0 {
>   			compatible = "ti,am62p-cpsw-mac-efuse", "syscon";
>   			reg = <0x2000 0x8>;
> diff --git a/arch/arm64/boot/dts/ti/k3-am62l3.dtsi b/arch/arm64/boot/dts/ti/k3-am62l3.dtsi
> index da220b85151227c63f59b2b8ec48ae2ebb37e7bf..f7146421918f7037c6a192cc4765e8814a508afc 100644
> --- a/arch/arm64/boot/dts/ti/k3-am62l3.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-am62l3.dtsi
> @@ -39,6 +39,8 @@ cpu0: cpu@0 {
>   			d-cache-line-size = <64>;
>   			d-cache-sets = <128>;
>   			next-level-cache = <&l2_0>;
> +			operating-points-v2 = <&a53_opp_table>;
> +			clocks = <&scmi_clk 356>;
>   		};
>   
>   		cpu1: cpu@1 {
> @@ -53,6 +55,8 @@ cpu1: cpu@1 {
>   			d-cache-line-size = <64>;
>   			d-cache-sets = <128>;
>   			next-level-cache = <&l2_0>;
> +			operating-points-v2 = <&a53_opp_table>;
> +			clocks = <&scmi_clk 356>;
>   		};
>   	};
>   
> @@ -64,4 +68,47 @@ l2_0: l2-cache0 {
>   		cache-line-size = <64>;
>   		cache-sets = <256>;
>   	};
> +
> +	a53_opp_table: opp-table {
> +		compatible = "operating-points-v2-ti-cpu";
> +		opp-shared;
> +		syscon = <&opp_efuse_table>;
> +
> +		opp-200000000 {
> +			opp-hz = /bits/ 64 <200000000>;
> +			opp-supported-hw = <0x01 0x0007>;
> +			clock-latency-ns = <6000000>;
> +		};
> +
> +		opp-400000000 {
> +			opp-hz = /bits/ 64 <400000000>;
> +			opp-supported-hw = <0x01 0x0007>;
> +			clock-latency-ns = <6000000>;
> +		};
> +
> +		opp-600000000 {
> +			opp-hz = /bits/ 64 <600000000>;
> +			opp-supported-hw = <0x01 0x0007>;
> +			clock-latency-ns = <6000000>;
> +		};
> +
> +		opp-800000000 {
> +			opp-hz = /bits/ 64 <800000000>;
> +			opp-supported-hw = <0x01 0x0007>;
> +			clock-latency-ns = <6000000>;
> +		};
> +
> +		opp-1000000000 {
> +			opp-hz = /bits/ 64 <1000000000>;
> +			opp-supported-hw = <0x01 0x0006>;
> +			clock-latency-ns = <6000000>;
> +		};
> +
> +		opp-1250000000 {
> +			opp-hz = /bits/ 64 <1250000000>;
> +			opp-supported-hw = <0x01 0x0003>;

What is determining the opp-supported-hw values? To my understanding 
based on the DT bindings docs, the values should be based on the number 
of unique speed grades, which there are two for AM62L. Looking at the 
values used here, it looks like it shows 3 unique speed grades.

By this logic, the value of opp-supported-hw should be something like 
0x03 for all OPPs below 833 MHz and 0x02 for all values above it.

> +			clock-latency-ns = <6000000>;
> +			opp-suspend;
> +		};
> +	};
>   };
> 

Best,
Kendall Willis <k-willis@...com>