Re: [PATCH 08/17] ARM: dts: samsung: exynos4210: use operating-points-v2

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] dts: missing opp-shared property causes conflicting cpufreq policies
--

commit fcba4068b9646df5bfbec161d06e3521379f32ed
Author: Henrik Grimler <henrik.grimler@axis.com>

ARM: dts: samsung: exynos4210: use operating-points-v2

This commit updates the exynos4210 device tree to use operating-points-v2
instead of the deprecated operating-points (v1) format. This resolves dt-check
style warnings about continuation-alignment.

> diff --git a/arch/arm/boot/dts/samsung/exynos4210.dtsi b/arch/arm/boot/dts/samsung/exynos4210.dtsi
> index d37ac0c97dbcf..4981bbb7cf311 100644
> --- a/arch/arm/boot/dts/samsung/exynos4210.dtsi
> +++ b/arch/arm/boot/dts/samsung/exynos4210.dtsi

[ ... ]

> @@ -263,6 +247,46 @@ opp-200000000 {
>  		};
>  	};
>  
> +	cpu_opp_table: opp-table-1 {
> +		compatible = "operating-points-v2";
> +

[Severity: High]
Does this new node need the opp-shared property?

CPU0 and CPU1 on this device share the CLK_ARM_CLK clock. When migrating to
operating-points-v2, the OPP framework relies on the opp-shared property to
know whether CPUs share the same clock line and therefore need a unified
cpufreq policy.

Without this property, the framework assumes the CPUs do not share the table:

drivers/opp/of.c:dev_pm_opp_of_get_sharing_cpus() {
    ...
    /* OPPs are shared ? */
    if (!of_property_read_bool(np, "opp-shared"))
        return 0;
    ...
}

Because the legacy v1 fallback logic is bypassed for v2 nodes, the cpufreq
driver will create independent policies and governors for CPU0 and CPU1. 

Since the cores share the same physical clock line, will this lead to the
independent governors issuing conflicting clk_set_rate requests, potentially
causing chaotic frequency switching and instability?

> +		opp-200000000 {
> +			opp-hz = /bits/ 64 <200000000>;
> +			opp-microvolt = <950000>;
> +			clock-latency-ns = <160000>;
> +		};

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261004-exynos-arm-cleanup-v1-0-45e435353c56@axis.com?part=8