iommu/arm-smmu-v3: Don't issue CMD_SYNC for zero-length invalidations

Calling arm_smmu_tlb_inv_range() with a size of zero, perhaps due to
an empty 'iommu_iotlb_gather' structure, should be a NOP. Elide the
CMD_SYNC when there is no invalidation to be performed.

Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 2be11a1..b7b3b0f 100644 (file)
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -1977,6 +1977,9 @@ static void arm_smmu_tlb_inv_range(unsigned long iova, size_t size,
                },
        };
 
+       if (!size)
+               return;
+
        if (smmu_domain->stage == ARM_SMMU_DOMAIN_S1) {
                cmd.opcode      = CMDQ_OP_TLBI_NH_VA;
                cmd.tlbi.asid   = smmu_domain->s1_cfg.cd.asid;