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

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Date: Fri, 29 Dec 2023 18:28:40 -0300
From: Nícolas F. R. A. Prado <nfraprado@...labora.com>
To: Viresh Kumar <viresh.kumar@...aro.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>
Cc: kernel@...labora.com,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Nícolas F. R. A. Prado <nfraprado@...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: [PATCH 2/2] arm64: dts: mediatek: cherry: Add CPU supply dependency to cpufreq-hw

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";
-- 
2.43.0