diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 7f41a47e7353..5b56a66063fd 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -769,6 +769,7 @@ static int amdgpu_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_reso
 
 		mem->bus.offset += adev->gmc.aper_base;
 		mem->bus.is_iomem = true;
+		mem->bus.caching = ttm_write_combined;
 		break;
 	default:
 		return -EINVAL;
diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
index 62235926e077..79151b1c157c 100644
--- a/drivers/gpu/drm/drm_gem_vram_helper.c
+++ b/drivers/gpu/drm/drm_gem_vram_helper.c
@@ -961,6 +961,7 @@ static int bo_driver_io_mem_reserve(struct ttm_bo_device *bdev,
 	case TTM_PL_VRAM:
 		mem->bus.offset = (mem->start << PAGE_SHIFT) + vmm->vram_base;
 		mem->bus.is_iomem = true;
+		mem->bus.caching = ttm_write_combined;
 		break;
 	default:
 		return -EINVAL;
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index 1d4b16c0e353..8ed30f471ec7 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -1124,6 +1124,8 @@ nouveau_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_resource *reg)
 	struct nouveau_drm *drm = nouveau_bdev(bdev);
 	struct nvkm_device *device = nvxx_device(&drm->client.device);
 	struct nouveau_mem *mem = nouveau_mem(reg);
+	struct nvif_mmu *mmu = &drm->client.mmu;
+	const u8 type = mmu->type[drm->ttm.type_vram].type;
 	int ret;
 
 	mutex_lock(&drm->ttm.io_reserve_mutex);
@@ -1139,6 +1141,7 @@ nouveau_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_resource *reg)
 			reg->bus.offset = (reg->start << PAGE_SHIFT) +
 				drm->agp.base;
 			reg->bus.is_iomem = !drm->agp.cma;
+			reg->bus.caching = ttm_write_combined;
 		}
 #endif
 		if (drm->client.mem->oclass < NVIF_CLASS_MEM_NV50 ||
@@ -1152,6 +1155,14 @@ nouveau_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_resource *reg)
 		reg->bus.offset = (reg->start << PAGE_SHIFT) +
 			device->func->resource_addr(device, 1);
 		reg->bus.is_iomem = true;
+
+		/* Some BARs do not support being ioremapped WC */
+		if (drm->client.device.info.family >= NV_DEVICE_INFO_V0_TESLA &&
+		    type & NVIF_MEM_UNCACHED)
+			reg->bus.caching = ttm_uncached;
+		else
+			reg->bus.caching = ttm_write_combined;
+
 		if (drm->client.mem->oclass >= NVIF_CLASS_MEM_NV50) {
 			union {
 				struct nv50_mem_map_v0 nv50;
diff --git a/drivers/gpu/drm/qxl/qxl_ttm.c b/drivers/gpu/drm/qxl/qxl_ttm.c
index dcf4ac1480c7..e79d4df99790 100644
--- a/drivers/gpu/drm/qxl/qxl_ttm.c
+++ b/drivers/gpu/drm/qxl/qxl_ttm.c
@@ -83,11 +83,13 @@ int qxl_ttm_io_mem_reserve(struct ttm_bo_device *bdev,
 	case TTM_PL_VRAM:
 		mem->bus.is_iomem = true;
 		mem->bus.offset = (mem->start << PAGE_SHIFT) + qdev->vram_base;
+		mem->bus.caching = ttm_cached;
 		break;
 	case TTM_PL_PRIV:
 		mem->bus.is_iomem = true;
 		mem->bus.offset = (mem->start << PAGE_SHIFT) +
 			qdev->surfaceram_base;
+		mem->bus.caching = ttm_cached;
 		break;
 	default:
 		return -EINVAL;
diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 130a7cea35c3..9b53a1d80632 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -372,6 +372,7 @@ static int radeon_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_reso
 			mem->bus.offset = (mem->start << PAGE_SHIFT) +
 				rdev->mc.agp_base;
 			mem->bus.is_iomem = !rdev->ddev->agp->cant_use_aperture;
+			mem->bus.caching = ttm_write_combined;
 		}
 #endif
 		break;
@@ -382,6 +383,7 @@ static int radeon_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_reso
 			return -EINVAL;
 		mem->bus.offset += rdev->mc.aper_base;
 		mem->bus.is_iomem = true;
+		mem->bus.caching = ttm_write_combined;
 #ifdef __alpha__
 		/*
 		 * Alpha: use bus.addr to hold the ioremap() return,
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
index 42f957d40c9f..2a7b5f964776 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
@@ -688,6 +688,7 @@ static int vmw_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_resourc
 		mem->bus.offset = (mem->start << PAGE_SHIFT) +
 			dev_priv->vram_start;
 		mem->bus.is_iomem = true;
+		mem->bus.caching = ttm_cached;
 		break;
 	default:
 		return -EINVAL;
diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index 0e172d94a0c1..91b67cecc6b6 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -29,6 +29,7 @@
 #include <linux/mutex.h>
 #include <linux/dma-fence.h>
 #include <drm/drm_print.h>
+#include <drm/ttm/ttm_caching.h>
 
 #define TTM_MAX_BO_PRIORITY	4U
 
@@ -148,9 +149,10 @@ struct ttm_resource_manager {
  * Structure indicating the bus placement of an object.
  */
 struct ttm_bus_placement {
-	void		*addr;
-	phys_addr_t	offset;
-	bool		is_iomem;
+	void			*addr;
+	phys_addr_t		offset;
+	bool			is_iomem;
+	enum ttm_caching	caching;
 };
 
 /**
