linux-kernel - [PATCH v2 2/2] arm64: dts: qcom: sc8280xp: Describe the PCIe SMMUv3

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Message-Id: <20231219-topic-8280_smmuv3-v2-2-c67bd3226687@linaro.org>
Date: Sat, 09 Mar 2024 14:31:10 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Bjorn Andersson <andersson@...nel.org>, 
 Rob Herring <robh+dt@...nel.org>, 
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
 Conor Dooley <conor+dt@...nel.org>, Will Deacon <will@...nel.org>, 
 Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>, 
 Rob Herring <robh@...nel.org>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>, 
 linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 iommu@...ts.linux.dev, Johan Hovold <johan+linaro@...nel.org>, 
 Konrad Dybcio <konrad.dybcio@...aro.org>
Subject: [PATCH v2 2/2] arm64: dts: qcom: sc8280xp: Describe the PCIe
 SMMUv3

SC8280XP actually has a third SMMU, which can be seen in e.g. the IORT
ACPI table and is used for the PCIe hosts.

Unfortunately though, the secure firmware seems to be configured in a
way such that Linux can't touch it, not even read back the ID registers.
It also seems like the SMMU is configured to run in some sort of bypass
mode, completely opaque to the OS.

Describe it so that one can configure it when running Linux as a
hypervisor (e.g with [1]) and for hardware description completeness.

[1] https://github.com/TravMurav/slbounce
Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
---
 arch/arm64/boot/dts/qcom/sc8280xp.dtsi | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
index a5b194813079..28edd30a9c04 100644
--- a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
+++ b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
@@ -4648,6 +4648,22 @@ cci3_i2c1_sleep: cci3-i2c1-sleep-pins {
 			};
 		};
 
+		pcie_smmu: iommu@...80000 {
+			compatible = "qcom,sc8280xp-smmu-v3", "arm,smmu-v3";
+			reg = <0 0x14f80000 0 0x80000>;
+			interrupts = <GIC_SPI 951 IRQ_TYPE_EDGE_RISING>,
+				     <GIC_SPI 955 IRQ_TYPE_EDGE_RISING>,
+				     <GIC_SPI 953 IRQ_TYPE_EDGE_RISING>;
+			interrupt-names = "eventq",
+					  "gerror",
+					  "cmdq-sync";
+			#iommu-cells = <1>;
+			dma-coherent;
+
+			/* The hypervisor prevents register access from Linux */
+			status = "reserved";
+		};
+
 		apps_smmu: iommu@...00000 {
 			compatible = "qcom,sc8280xp-smmu-500", "arm,mmu-500";
 			reg = <0 0x15000000 0 0x100000>;

-- 
2.44.0