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

From: Viresh Kumar <viresh.kumar@linaro.org>
To: "Nícolas F. R. A. Prado" <nfraprado@collabora.com>
Cc: "Rafael J . Wysocki" <rafael@kernel.org>,
	kernel@collabora.com,
	AngeloGioacchino Del Regno
	<angelogioacchino.delregno@collabora.com>,
	Conor Dooley <conor+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org
Subject: Re: [PATCH 2/2] arm64: dts: mediatek: cherry: Add CPU supply dependency to cpufreq-hw
Date: Tue, 2 Jan 2024 11:41:23 +0530	[thread overview]
Message-ID: <20240102061123.frvwltggqqh6m7pm@vireshk-i7> (raw)
In-Reply-To: <20231229212853.277334-2-nfraprado@collabora.com>

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@collabora.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