[PATCH 02/13] iommu/arm-smmu: Install bypass S2CRs for IOMMU_DOMAIN_IDENTITY domains

[Manoj Iyer]

From: Will Deacon <will.deacon at arm.com>

In preparation for allowing the default domain type to be overridden,
this patch adds support for IOMMU_DOMAIN_IDENTITY domains to the
ARM SMMU driver.

An identity domain is created by placing the corresponding S2CR
registers into "bypass" mode, which allows transactions to flow through
the SMMU without any translation.

BugLink: http://bugs.launchpad.net/bugs/1688158

Reviewed-by: Robin Murphy <robin.murphy at arm.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
(cherry picked from commit 61bc671179f19060be883068b6d3d82ae0b24bc0)
Signed-off-by: Manoj Iyer <manoj.iyer at canonical.com>
---
 drivers/iommu/arm-smmu.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index f819b1553160..9596f1b760e0 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -413,6 +413,7 @@ enum arm_smmu_domain_stage {
 	ARM_SMMU_DOMAIN_S1 = 0,
 	ARM_SMMU_DOMAIN_S2,
 	ARM_SMMU_DOMAIN_NESTED,
+	ARM_SMMU_DOMAIN_BYPASS,
 };
 
 struct arm_smmu_domain {
@@ -835,6 +836,12 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 	if (smmu_domain->smmu)
 		goto out_unlock;
 
+	if (domain->type == IOMMU_DOMAIN_IDENTITY) {
+		smmu_domain->stage = ARM_SMMU_DOMAIN_BYPASS;
+		smmu_domain->smmu = smmu;
+		goto out_unlock;
+	}
+
 	/*
 	 * Mapping the requested stage onto what we support is surprisingly
 	 * complicated, mainly because the spec allows S1+S2 SMMUs without
@@ -995,7 +1002,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
 	void __iomem *cb_base;
 	int irq;
 
-	if (!smmu)
+	if (!smmu || domain->type == IOMMU_DOMAIN_IDENTITY)
 		return;
 
 	/*
@@ -1018,7 +1025,9 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
 {
 	struct arm_smmu_domain *smmu_domain;
 
-	if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
+	if (type != IOMMU_DOMAIN_UNMANAGED &&
+	    type != IOMMU_DOMAIN_DMA &&
+	    type != IOMMU_DOMAIN_IDENTITY)
 		return NULL;
 	/*
 	 * Allocate the domain and initialise some of its data structures.
@@ -1247,10 +1256,15 @@ static int arm_smmu_domain_add_master(struct arm_smmu_domain *smmu_domain,
 {
 	struct arm_smmu_device *smmu = smmu_domain->smmu;
 	struct arm_smmu_s2cr *s2cr = smmu->s2crs;
-	enum arm_smmu_s2cr_type type = S2CR_TYPE_TRANS;
 	u8 cbndx = smmu_domain->cfg.cbndx;
+	enum arm_smmu_s2cr_type type;
 	int i, idx;
 
+	if (smmu_domain->stage == ARM_SMMU_DOMAIN_BYPASS)
+		type = S2CR_TYPE_BYPASS;
+	else
+		type = S2CR_TYPE_TRANS;
+
 	for_each_cfg_sme(fwspec, i, idx) {
 		if (type == s2cr[idx].type && cbndx == s2cr[idx].cbndx)
 			continue;
-- 
2.11.0