From: Konrad Dybcio <konrad.dybcio@oss.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@linaro.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@oss.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@15000000 {
 				     <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@150c5000 {

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

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

On Tue, 25 Feb 2025 14:44:40 +0100, Konrad Dybcio wrote:
> 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).
> 
> [...]

Applied, thanks!

[1/1] Revert "arm64: dts: qcom: sdm845: Affirm IDR0.CCTW on apps_smmu"
      commit: f00db31d235946853fb430de8c6aa1295efc8353

Best regards,
-- 
Bjorn Andersson <andersson@kernel.org>

On Tue, Feb 25, 2025 at 02:44:40PM +0100, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@oss.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@linaro.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@oss.qualcomm.com>
> ---
>  arch/arm64/boot/dts/qcom/sdm845.dtsi | 1 -
>  1 file changed, 1 deletion(-)

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Should we enable dma-coherent for RB3 only then?


-- 
With best wishes
Dmitry