linux-kernel - [PATCH] Revert "arm64: dts: qcom: sdm845: Affirm IDR0.CCTW on apps

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Message-Id: <20250225-topic-845_smmu_not_coherent-v1-1-98ca9d17471c@oss.qualcomm.com>
Date: Tue, 25 Feb 2025 14:44:40 +0100
From: Konrad Dybcio <konradybcio@...nel.org>
To: Bjorn Andersson <andersson@...nel.org>, 
 Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>, 
 Konrad Dybcio <quic_kdybcio@...cinc.com>, linux-arm-msm@...r.kernel.org, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Konrad Dybcio <konrad.dybcio@....qualcomm.com>, 
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: [PATCH] Revert "arm64: dts: qcom: sdm845: Affirm IDR0.CCTW on
 apps_smmu"

From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>

There are reports that the pagetable walker cache coherency is not a
given across the spectrum of SDM845/850 devices, leading to lock-ups
and resets. It works fine on some devices (like the Dragonboard 845c,
but not so much on the Lenovo Yoga C630).

This unfortunately looks like a fluke in firmware development, where
likely somewhere in the vast hypervisor stack, a change to accommodate
for this was only introduced after the initial software release (which
often serves as a baseline for products).

Revert the change to avoid additional guesswork around crashes.

This reverts commit 6b31a9744b8726c69bb0af290f8475a368a4b805.

Reported-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Closes: https://lore.kernel.org/linux-arm-msm/20250215-yoga-dma-coherent-v1-1-2419ee184a81@linaro.org/
Fixes: 6b31a9744b87 ("arm64: dts: qcom: sdm845: Affirm IDR0.CCTW on apps_smmu")
Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
---
 arch/arm64/boot/dts/qcom/sdm845.dtsi | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi
index e0ce804bb1a35047b092d4745988170738a3cd03..d0314cdf0b92fd282915e7184f88b52bf309b2c2 100644
--- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
+++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
@@ -5163,7 +5163,6 @@ apps_smmu: iommu@...00000 {
 				     <GIC_SPI 341 IRQ_TYPE_LEVEL_HIGH>,
 				     <GIC_SPI 342 IRQ_TYPE_LEVEL_HIGH>,
 				     <GIC_SPI 343 IRQ_TYPE_LEVEL_HIGH>;
-			dma-coherent;
 		};
 
 		anoc_1_tbu: tbu@...c5000 {

---
base-commit: 0226d0ce98a477937ed295fb7df4cc30b46fc304
change-id: 20250225-topic-845_smmu_not_coherent-248019b99e7e

Best regards,
-- 
Konrad Dybcio <konrad.dybcio@....qualcomm.com>