iommu/qcom: Disable and reset context bank before programming

Writing	the new	TTBRs, TCRs and MAIRs on a previously enabled
context bank may trigger a context fault, resulting in firmware
driven AP resets: change the domain initialization programming
sequence to disable the context bank(s) and to also clear the
related fault address (CB_FAR) and fault status (CB_FSR)
registers before writing new values to TTBR0/1, TCR/TCR2, MAIR0/1.

Fixes: 0ae349a ("iommu/qcom: Add qcom_iommu")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230622092742.74819-4-angelogioacchino.delregno@collabora.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: AngeloGioacchino Del Regno

drivers/iommu/arm/arm-smmu/qcom_iommu.c

@@ -273,6 +273,13 @@ static int qcom_iommu_init_domain(struct iommu_domain *domain,
 			ctx->secure_init = true;
 		}
 
+		/* Disable context bank before programming */
+		iommu_writel(ctx, ARM_SMMU_CB_SCTLR, 0);
+
+		/* Clear context bank fault address fault status registers */
+		iommu_writel(ctx, ARM_SMMU_CB_FAR, 0);
+		iommu_writel(ctx, ARM_SMMU_CB_FSR, ARM_SMMU_FSR_FAULT);
+
 		/* TTBRs */
 		iommu_writeq(ctx, ARM_SMMU_CB_TTBR0,
 				pgtbl_cfg.arm_lpae_s1_cfg.ttbr |