drm/msm: don't return NULL from msm_iommu_new()

As we've dropped no-IOMMU support, there is no reason to specially
handle the no-IOMMU case inside msm_iommu_new(). Make it return -ENODEV
if there is no IOMMU (instead of returning NULL) and simplify all
calling sites accordingly.

Signed-off-by: Dmitry Baryshkov <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/672561/
Signed-off-by: Rob Clark <[e-mail]>

drivers/gpu/drm/msm/adreno/a6xx_gmu.c

···
 	struct msm_mmu *mmu;
 
 	mmu = msm_iommu_new(gmu->dev, 0);
-	if (!mmu)
-		return -ENODEV;
 	if (IS_ERR(mmu))
 		return PTR_ERR(mmu);
 

drivers/gpu/drm/msm/adreno/adreno_gpu.c

···
 	u64 start, size;
 
 	mmu = msm_iommu_gpu_new(&pdev->dev, gpu, quirks);
-	if (!mmu)
-		return ERR_PTR(-ENODEV);
-	else if (IS_ERR_OR_NULL(mmu))
+	if (IS_ERR(mmu))
 		return ERR_CAST(mmu);
 
 	geometry = msm_iommu_get_geometry(mmu);

drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c

···
 	mdp4_disable(mdp4_kms);
 	mdelay(16);
 
+	if (!device_iommu_mapped(&pdev->dev)) {
+		DRM_DEV_INFO(dev->dev, "no IOMMU, bailing out\n");
+		ret = -ENODEV;
+		goto fail;
+	}
+
 	mmu = msm_iommu_new(&pdev->dev, 0);
 	if (IS_ERR(mmu)) {
 		ret = PTR_ERR(mmu);
-		goto fail;
-	} else if (!mmu) {
-		DRM_DEV_INFO(dev->dev, "no IOMMU, bailing out\n");
-		ret = -ENODEV;
 		goto fail;
 	} else {
 		vm  = msm_gem_vm_create(dev, mmu, "mdp4",

drivers/gpu/drm/msm/msm_iommu.c

···
 	int ret;
 
 	if (!device_iommu_mapped(dev))
-		return NULL;
+		return ERR_PTR(-ENODEV);
 
 	domain = iommu_paging_domain_alloc(dev);
 	if (IS_ERR(domain))
···
 	struct msm_mmu *mmu;
 
 	mmu = msm_iommu_new(dev, quirks);
-	if (IS_ERR_OR_NULL(mmu))
+	if (IS_ERR(mmu))
 		return mmu;
 
 	iommu = to_msm_iommu(mmu);
···
 	struct msm_mmu *mmu;
 
 	mmu = msm_iommu_new(dev, quirks);
-	if (IS_ERR_OR_NULL(mmu))
+	if (IS_ERR(mmu))
 		return mmu;
 
 	iommu = to_msm_iommu(mmu);

drivers/gpu/drm/msm/msm_kms.c

···
 	 */
 	if (device_iommu_mapped(mdp_dev))
 		iommu_dev = mdp_dev;
-	else
+	else if (device_iommu_mapped(mdss_dev))
 		iommu_dev = mdss_dev;
-	mmu = msm_iommu_disp_new(iommu_dev, 0);
-	if (IS_ERR(mmu))
-		return ERR_CAST(mmu);
-
-	if (!mmu) {
+	else {
 		drm_info(dev, "no IOMMU, bailing out\n");
 		return ERR_PTR(-ENODEV);
 	}
+
+	mmu = msm_iommu_disp_new(iommu_dev, 0);
+	if (IS_ERR(mmu))
+		return ERR_CAST(mmu);
 
 	vm = msm_gem_vm_create(dev, mmu, "mdp_kms",
 			       0x1000, 0x100000000 - 0x1000, true);