drm/amdgpu: enable S/G display on PCO and RV2 (v2)

It should work on all Raven variants, but some users have
reported issues with original Raven with IOMMU enabled.
So far there have been no issues observed with PCO or RV2.

v2: split out the dm init and domain changes into separate
patches.

Acked-by: Harry Wentland <[e-mail]>
Acked-by: Huang Rui <[e-mail]>
Acked-by: Christian König <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_display.c

···
 	 * will not allow USWC mappings.
 	 * Also, don't allow GTT domain if the BO doens't have USWC falg set.
 	 */
-	if (adev->asic_type >= CHIP_CARRIZO &&
-	    adev->asic_type < CHIP_RAVEN &&
-	    (adev->flags & AMD_IS_APU) &&
-	    (bo_flags & AMDGPU_GEM_CREATE_CPU_GTT_USWC) &&
+	if ((bo_flags & AMDGPU_GEM_CREATE_CPU_GTT_USWC) &&
 	    amdgpu_bo_support_uswc(bo_flags) &&
-	    amdgpu_device_asic_has_dc_support(adev->asic_type))
-		domain |= AMDGPU_GEM_DOMAIN_GTT;
+	    amdgpu_device_asic_has_dc_support(adev->asic_type)) {
+		switch (adev->asic_type) {
+		case CHIP_CARRIZO:
+		case CHIP_STONEY:
+			domain |= AMDGPU_GEM_DOMAIN_GTT;
+			break;
+		case CHIP_RAVEN:
+			/* enable S/G on PCO and RV2 */
+			if (adev->rev_id >= 0x8 || adev->pdev->device == 0x15d8)
+				domain |= AMDGPU_GEM_DOMAIN_GTT;
+			break;
+		default:
+			break;
+		}
+	}
 #endif
 
 	return domain;