Please use below two changes to disable SMMU for PCIe.
(The first change shows how it is to be done for the C5 controller. If the controller in question is not C5, then, a similar change needs to be made for the respective controller.
The second change is a common change.)
--- a/kernel-dts/tegra194-soc/tegra194-soc-pcie.dtsi
+++ b/kernel-dts/tegra194-soc/tegra194-soc-pcie.dtsi
@@ -867,13 +867,6 @@
pinctrl-0 = <&pex_rst_c5_out_state>;
pinctrl-1 = <&clkreq_c5_bi_dir_state>;
- iommus = <&smmu TEGRA_SID_PCIE5>;
- dma-coherent;
-#if LINUX_VERSION >= 414
- iommu-map = <0x0 &smmu TEGRA_SID_PCIE5 0x1000>;
- iommu-map-mask = <0x0>;
-#endif
-
#interrupt-cells = <1>;
interrupt-map-mask = <0 0 0 0>;
interrupt-map = <0 0 0 0 &intc 0 53 0x04>;
and
--- a/drivers/iommu/arm-smmu-t19x.c
+++ b/drivers/iommu/arm-smmu-t19x.c
@@ -2535,7 +2535,10 @@ static void arm_smmu_device_reset(struct arm_smmu_device *smmu)
reg = readl_relaxed(ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);
/* Enable fault reporting */
- reg |= (sCR0_GFRE | sCR0_GFIE | sCR0_GCFGFRE | sCR0_GCFGFIE | sCR0_USFCFG);
+ reg |= (sCR0_GFRE | sCR0_GFIE | sCR0_GCFGFRE | sCR0_GCFGFIE);
+
+ /* Disable Unidentified stream fault reporting */
+ reg &= ~(sCR0_USFCFG);
/* Disable TLB broadcasting. */
reg |= (sCR0_VMIDPNE | sCR0_PTM);