mem->bus.offset += adev->gmc.aper_base;
                mem->bus.is_iomem = true;
+               mem->bus.caching = ttm_write_combined;
                break;
        default:
                return -EINVAL;
 
        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;
 
        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);
                        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 ||
                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;
 
        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;
 
                        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;
                        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,
 
                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;
 
 #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
 
  * 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;
 };
 
 /**