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[5/5] iommu/arm-smmu: prefer stage-1 mappings where we have a choice

Message ID 1404125530-17984-6-git-send-email-will.deacon@arm.com
State Accepted
Commit 9c5c92e35cf5c4f7ee523d62a6bf9d5dc290350b
Headers show

Commit Message

Will Deacon June 30, 2014, 10:52 a.m. UTC
For an SMMU that supports both Stage-1 and Stage-2 mappings (but not
nested translation), then we should prefer stage-1 mappings as we
otherwise rely on the memory attributes of the incoming transactions
for IOMMU_CACHE mappings.

Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 drivers/iommu/arm-smmu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Leizhen (ThunderTown) July 9, 2014, 6:36 a.m. UTC | #1
On 2014/6/30 18:52, Will Deacon wrote:
> For an SMMU that supports both Stage-1 and Stage-2 mappings (but not
> nested translation), then we should prefer stage-1 mappings as we
> otherwise rely on the memory attributes of the incoming transactions
> for IOMMU_CACHE mappings.
> 
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
>  drivers/iommu/arm-smmu.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 60986de3ada8..a6e38982d09c 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -876,12 +876,12 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
>  		 */
>  		cfg->cbar = CBAR_TYPE_S1_TRANS_S2_BYPASS;
>  		start = smmu->num_s2_context_banks;
> -	} else if (smmu->features & ARM_SMMU_FEAT_TRANS_S2) {
> -		cfg->cbar = CBAR_TYPE_S2_TRANS;
> -		start = 0;
> -	} else {
> +	} else if (smmu->features & ARM_SMMU_FEAT_TRANS_S1) {
>  		cfg->cbar = CBAR_TYPE_S1_TRANS_S2_BYPASS;
>  		start = smmu->num_s2_context_banks;
> +	} else {
> +		cfg->cbar = CBAR_TYPE_S2_TRANS;
> +		start = 0;
>  	}
>  
>  	ret = __arm_smmu_alloc_bitmap(smmu->context_map, start,
> 
Why not change ARM_SMMU_FEAT_TRANS_NESTED to ARM_SMMU_FEAT_TRANS_S1 in the
former if stagement? Then we can merge the two branches, actually it is the
same. NESTED means both S1 and S2.

thunder
diff mbox

Patch

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 60986de3ada8..a6e38982d09c 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -876,12 +876,12 @@  static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 		 */
 		cfg->cbar = CBAR_TYPE_S1_TRANS_S2_BYPASS;
 		start = smmu->num_s2_context_banks;
-	} else if (smmu->features & ARM_SMMU_FEAT_TRANS_S2) {
-		cfg->cbar = CBAR_TYPE_S2_TRANS;
-		start = 0;
-	} else {
+	} else if (smmu->features & ARM_SMMU_FEAT_TRANS_S1) {
 		cfg->cbar = CBAR_TYPE_S1_TRANS_S2_BYPASS;
 		start = smmu->num_s2_context_banks;
+	} else {
+		cfg->cbar = CBAR_TYPE_S2_TRANS;
+		start = 0;
 	}
 
 	ret = __arm_smmu_alloc_bitmap(smmu->context_map, start,