linux-kernel - [PATCH] arm64: dts: mediatek: mt8195: Set DSU PMU status to fail

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Message-ID: <20230720200753.322133-1-nfraprado@collabora.com>
Date:   Thu, 20 Jul 2023 16:07:51 -0400
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
Cc:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, kernel@...labora.com,
        Chen-Yu Tsai <wenst@...omium.org>,
        Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>, Conor Dooley <conor+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Seiya Wang <seiya.wang@...iatek.com>,
        Tinghan Shen <tinghan.shen@...iatek.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org
Subject: [PATCH] arm64: dts: mediatek: mt8195: Set DSU PMU status to fail

The DSU PMU allows monitoring performance events in the DSU cluster,
which is done by configuring and reading back values from the DSU PMU
system registers. However, for write-access to be allowed by ELs lower
than EL3, the EL3 firmware needs to update the setting on the ACTLR3_EL3
register, as it is disallowed by default.

That configuration is not done on the firmware used by the MT8195 SoC,
as a consequence, booting a MT8195-based machine like
mt8195-cherry-tomato-r2 with CONFIG_ARM_DSU_PMU enabled hangs the kernel
just as it writes to the CLUSTERPMOVSCLR_EL1 register, since the
instruction faults to EL3, and BL31 apparently just re-runs the
instruction over and over.

Mark the DSU PMU node in the Devicetree with status "fail", as the
machine doesn't have a suitable firmware to make use of it from the
kernel, and allowing its driver to probe would hang the kernel.

Fixes: 37f2582883be ("arm64: dts: Add mediatek SoC mt8195 and evaluation board")
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>

---

 arch/arm64/boot/dts/mediatek/mt8195.dtsi | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/boot/dts/mediatek/mt8195.dtsi b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
index 5c670fce1e47..0705d9c3a6a7 100644
--- a/arch/arm64/boot/dts/mediatek/mt8195.dtsi
+++ b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
@@ -313,6 +313,7 @@ dsu-pmu {
 		interrupts = <GIC_SPI 18 IRQ_TYPE_LEVEL_HIGH 0>;
 		cpus = <&cpu0>, <&cpu1>, <&cpu2>, <&cpu3>,
 		       <&cpu4>, <&cpu5>, <&cpu6>, <&cpu7>;
+		status = "fail";
 	};

 	dmic_codec: dmic-codec {
-- 
2.41.0