NVIDIA: SAUCE: iommu/arm-smmu-v3: Allow default substream bypass with a pasid support

When an iommu_domain is set to IOMMU_DOMAIN_IDENTITY, the driver would
skip the allocation of a CD table and set the CONFIG field of the STE
to STRTAB_STE_0_CFG_BYPASS. This works well for devices that only have
one substream, i.e. PASID disabled.

However, there could be a use case, for a pasid capable device, that
allows bypassing the translation at the default substream while still
enabling the pasid feature, which means the driver should not skip the
allocation of a CD table nor simply bypass the CONFIG field. Instead,
the S1DSS field should be set to STRTAB_STE_1_S1DSS_BYPASS and the
SHCFG field should be set to STRTAB_STE_1_SHCFG_INCOMING.

Add s1dss in struct arm_smmu_s1_cfg, to allow a configuration in the
finalise() to support this use case.

Also, according to "13.5 Summary of attribute/permission configuration
fields" in the reference manual, the SHCFG field value is irrelevant.
So, set the SHCFG field of the STE always to STRTAB_STE_1_SHCFG_INCOMING
for simplification.

Signed-off-by: Nicolin Chen <[email protected]>
Reviewed-by: Pritesh Raithatha <[email protected]>
Acked-by: Jamie Nguyen <[email protected]>
Acked-by: Nicolin Chen <[email protected]>

Author: nicolinc

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

@@ -1332,7 +1332,8 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
 
 		BUG_ON(ste_live);
 		dst[1] = cpu_to_le64(
-			 FIELD_PREP(STRTAB_STE_1_S1DSS, STRTAB_STE_1_S1DSS_SSID0) |
+			 FIELD_PREP(STRTAB_STE_1_S1DSS, s1_cfg->s1dss) |
+			 FIELD_PREP(STRTAB_STE_1_SHCFG, STRTAB_STE_1_SHCFG_INCOMING) |
 			 FIELD_PREP(STRTAB_STE_1_S1CIR, STRTAB_STE_1_S1C_CACHE_WBRA) |
 			 FIELD_PREP(STRTAB_STE_1_S1COR, STRTAB_STE_1_S1C_CACHE_WBRA) |
 			 FIELD_PREP(STRTAB_STE_1_S1CSH, ARM_SMMU_SH_ISH) |
@@ -2099,6 +2100,10 @@ static int arm_smmu_domain_finalise_s1(struct arm_smmu_domain *smmu_domain,
 		goto out_unlock;
 
 	cfg->s1cdmax = master->ssid_bits;
+	if (smmu_domain->domain.type == IOMMU_DOMAIN_IDENTITY)
+		cfg->s1dss = STRTAB_STE_1_S1DSS_BYPASS;
+	else
+		cfg->s1dss = STRTAB_STE_1_S1DSS_SSID0;
 
 	smmu_domain->stall_enabled = master->stall_enabled;
 
@@ -2178,7 +2183,11 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain,
 	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
 	struct arm_smmu_device *smmu = smmu_domain->smmu;
 
-	if (domain->type == IOMMU_DOMAIN_IDENTITY) {
+	/*
+	 * A master with a pasid capability might need a CD table, so only set
+	 * ARM_SMMU_DOMAIN_BYPASS if IOMMU_DOMAIN_IDENTITY and non-pasid master
+	 */
+	if (domain->type == IOMMU_DOMAIN_IDENTITY && !master->ssid_bits) {
 		smmu_domain->stage = ARM_SMMU_DOMAIN_BYPASS;
 		return 0;
 	}

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

@@ -595,6 +595,7 @@ struct arm_smmu_s1_cfg {
 	struct arm_smmu_ctx_desc_cfg	cdcfg;
 	struct arm_smmu_ctx_desc	cd;
 	u8				s1fmt;
+	u8				s1dss;
 	u8				s1cdmax;
 };