iommu/msm: Implement an IDENTITY domain

What msm does during msm_iommu_set_platform_dma() is actually putting the
iommu into identity mode.

Move to the new core support for ARM_DMA_USE_IOMMU by defining
ops->identity_domain.

This driver does not support IOMMU_DOMAIN_DMA, however it cannot be
compiled on ARM64 either. Most likely it is fine to support dma-iommu.c

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/14-v8-81230027b2fa+9d-iommu_all_defdom_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/msm_iommu.c

@@ -443,15 +443,20 @@ static int msm_iommu_attach_dev(struct iommu_domain *domain, struct device *dev)
 	return ret;
 }
 
-static void msm_iommu_set_platform_dma(struct device *dev)
+static int msm_iommu_identity_attach(struct iommu_domain *identity_domain,
+				     struct device *dev)
 {
 	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
-	struct msm_priv *priv = to_msm_priv(domain);
+	struct msm_priv *priv;
 	unsigned long flags;
 	struct msm_iommu_dev *iommu;
 	struct msm_iommu_ctx_dev *master;
-	int ret;
+	int ret = 0;
+
+	if (domain == identity_domain || !domain)
+		return 0;
 
+	priv = to_msm_priv(domain);
 	free_io_pgtable_ops(priv->iop);
 
 	spin_lock_irqsave(&msm_iommu_lock, flags);
@@ -468,8 +473,18 @@ static void msm_iommu_set_platform_dma(struct device *dev)
 	}
 fail:
 	spin_unlock_irqrestore(&msm_iommu_lock, flags);
+	return ret;
 }
 
+static struct iommu_domain_ops msm_iommu_identity_ops = {
+	.attach_dev = msm_iommu_identity_attach,
+};
+
+static struct iommu_domain msm_iommu_identity_domain = {
+	.type = IOMMU_DOMAIN_IDENTITY,
+	.ops = &msm_iommu_identity_ops,
+};
+
 static int msm_iommu_map(struct iommu_domain *domain, unsigned long iova,
 			 phys_addr_t pa, size_t pgsize, size_t pgcount,
 			 int prot, gfp_t gfp, size_t *mapped)
@@ -675,10 +690,10 @@ irqreturn_t msm_iommu_fault_handler(int irq, void *dev_id)
 }
 
 static struct iommu_ops msm_iommu_ops = {
+	.identity_domain = &msm_iommu_identity_domain,
 	.domain_alloc = msm_iommu_domain_alloc,
 	.probe_device = msm_iommu_probe_device,
 	.device_group = generic_device_group,
-	.set_platform_dma_ops = msm_iommu_set_platform_dma,
 	.pgsize_bitmap = MSM_IOMMU_PGSIZES,
 	.of_xlate = qcom_iommu_of_xlate,
 	.default_domain_ops = &(const struct iommu_domain_ops) {