linux-kernel - Re: [PATCH 2/2] arm64: dts: mediatek: cherry: Add CPU supply dependency to cpufreq-hw

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Message-ID: <20240102061123.frvwltggqqh6m7pm@vireshk-i7>
Date: Tue, 2 Jan 2024 11:41:23 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Nícolas F. R. A. Prado <nfraprado@...labora.com>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>, kernel@...labora.com,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Conor Dooley <conor+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 2/2] arm64: dts: mediatek: cherry: Add CPU supply
 dependency to cpufreq-hw

On 29-12-23, 18:28, Nícolas F. R. A. Prado wrote:
> When the mediatek-cpufreq-hw driver enables the hardware (by
> writing to REG_FREQ_ENABLE), if the regulator supplying the voltage to
> the big CPUs hasn't probed yet, the platform hangs shortly after and
> "rcu: INFO: rcu_preempt detected stalls on CPUs/tasks" are printed in
> the log.
> 
> To prevent this from happening, describe the big CPUs regulator in the
> performance-controller DT node, so that devlink ensures the regulator
> has been probed and configured before the frequency scaling hardware is
> probed and enabled.
> 
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> 
> ---
> 
>  arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi b/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi
> index dd5b89b73190..505da60eee90 100644
> --- a/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi
> +++ b/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi
> @@ -502,6 +502,10 @@ &pcie1 {
>  	pinctrl-0 = <&pcie1_pins_default>;
>  };
>  
> +&performance {
> +	big-cpus-supply = <&mt6315_6_vbuck1>;
> +};
> +
>  &pio {
>  	mediatek,rsel-resistance-in-si-unit;
>  	pinctrl-names = "default";

I think the regulator needs to be mentioned in the CPU's node and not
here ?

-- 
viresh