[RFC PATCH 04/30] iommu/arm-smmu-v3: Add support for PCI ATS

[Sunil Kovvuri]

> +static size_t arm_smmu_atc_invalidate_domain(struct arm_smmu_domain *smmu_domain,
> +                                            unsigned long iova, size_t size)
> +{
> +       unsigned long flags;
> +       struct arm_smmu_cmdq_ent cmd = {0};
> +       struct arm_smmu_group *smmu_group;
> +       struct arm_smmu_master_data *master;
> +       struct arm_smmu_device *smmu = smmu_domain->smmu;
> +       struct arm_smmu_cmdq_ent sync_cmd = {
> +               .opcode = CMDQ_OP_CMD_SYNC,
> +       };
> +
> +       spin_lock_irqsave(&smmu_domain->groups_lock, flags);
> +
> +       list_for_each_entry(smmu_group, &smmu_domain->groups, domain_head) {
> +               if (!smmu_group->ats_enabled)
> +                       continue;

If ATS is not supported, this seems to increase no of cycles spent in
pgtbl_lock.
Can we return from this API by checking 'ARM_SMMU_FEAT_ATS' in smmu->features ?

Thanks,
Sunil.