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

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Message-ID: <20260122103606.wsuwl7pyyfxo5xlw@lcpd911>
Date: Thu, 22 Jan 2026 16:06:06 +0530
From: Dhruva Gole <d-gole@...com>
To: Kendall Willis <k-willis@...com>
CC: "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>, 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 Jan 21, 2026 at 10:27:15 -0600, Kendall Willis wrote:
> 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.

That's an astute observation indeed, and I will go fix it right now.
Thanks for reviewing thoroughly! I will anyway send this patch on it's
own now that the driver patches are merged and the DT needs to go
separately at this point.

-- 
Best regards,
Dhruva Gole
Texas Instruments Incorporated