iommu/arm-smmu-v3: Document nesting-related errata

Both MMU-600 and MMU-700 have similar errata around TLB invalidation
while both stages of translation are active, which will need some
consideration once nesting support is implemented. For now, though,
it's very easy to make our implicit lack of nesting support explicit
for those cases, so they're less likely to be missed in future.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Link: https://lore.kernel.org/r/696da78d32bb4491f898f11b0bb4d850a8aa7c6a.1683731256.git.robin.murphy@arm.comSigned-off-by: Will Deacon <will@kernel.org>

Documentation/arm64/silicon-errata.rst

@@ -140,9 +140,9 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | MMU-500         | #841119,826419  | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
-| ARM            | MMU-600         | #1076982        | N/A                         |
+| ARM            | MMU-600         | #1076982,1209401| N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
-| ARM            | MMU-700         | #2812531        | N/A                         |
+| ARM            | MMU-700         | #2268618,2812531| N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+
 | Broadcom       | Brahma-B53      | N/A             | ARM64_ERRATUM_845719        |

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -3457,11 +3457,16 @@ static void arm_smmu_device_iidr_probe(struct arm_smmu_device *smmu)
 			/* Arm erratum 1076982 */
 			if (variant == 0 && revision <= 2)
 				smmu->features &= ~ARM_SMMU_FEAT_SEV;
+			/* Arm erratum 1209401 */
+			if (variant < 2)
+				smmu->features &= ~ARM_SMMU_FEAT_NESTING;
 			break;
 		case IIDR_PRODUCTID_ARM_MMU_700:
 			/* Arm erratum 2812531 */
 			smmu->features &= ~ARM_SMMU_FEAT_BTM;
 			smmu->options |= ARM_SMMU_OPT_CMDQ_FORCE_SYNC;
+			/* Arm errata 2268618, 2812531 */
+			smmu->features &= ~ARM_SMMU_FEAT_NESTING;
 			break;
 		}
 		break;