drm/ttm: expose CPU address of DMA-allocated pages

Pages allocated using the DMA API have a coherent memory mapping. Make
this mapping visible to drivers so they can decide to use it instead of
creating their own redundant one.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: David Airlie <airlied@linux.ie>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/ttm/ttm_page_alloc_dma.c

@@ -848,6 +848,7 @@ static int ttm_dma_pool_get_pages(struct dma_pool *pool,
 	if (count) {
 		d_page = list_first_entry(&pool->free_list, struct dma_page, page_list);
 		ttm->pages[index] = d_page->p;
+		ttm_dma->cpu_address[index] = d_page->vaddr;
 		ttm_dma->dma_address[index] = d_page->dma;
 		list_move_tail(&d_page->page_list, &ttm_dma->pages_list);
 		r = 0;
@@ -979,6 +980,7 @@ void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev)
 	INIT_LIST_HEAD(&ttm_dma->pages_list);
 	for (i = 0; i < ttm->num_pages; i++) {
 		ttm->pages[i] = NULL;
+		ttm_dma->cpu_address[i] = 0;
 		ttm_dma->dma_address[i] = 0;
 	}
 

drivers/gpu/drm/ttm/ttm_tt.c

@@ -55,9 +55,12 @@ static void ttm_tt_alloc_page_directory(struct ttm_tt *ttm)
 
 static void ttm_dma_tt_alloc_page_directory(struct ttm_dma_tt *ttm)
 {
-	ttm->ttm.pages = drm_calloc_large(ttm->ttm.num_pages, sizeof(void*));
-	ttm->dma_address = drm_calloc_large(ttm->ttm.num_pages,
-					    sizeof(*ttm->dma_address));
+	ttm->ttm.pages = drm_calloc_large(ttm->ttm.num_pages,
+					  sizeof(*ttm->ttm.pages) +
+					  sizeof(*ttm->dma_address) +
+					  sizeof(*ttm->cpu_address));
+	ttm->cpu_address = (void *) (ttm->ttm.pages + ttm->ttm.num_pages);
+	ttm->dma_address = (void *) (ttm->cpu_address + ttm->ttm.num_pages);
 }
 
 #ifdef CONFIG_X86
@@ -228,7 +231,7 @@ int ttm_dma_tt_init(struct ttm_dma_tt *ttm_dma, struct ttm_bo_device *bdev,
 
 	INIT_LIST_HEAD(&ttm_dma->pages_list);
 	ttm_dma_tt_alloc_page_directory(ttm_dma);
-	if (!ttm->pages || !ttm_dma->dma_address) {
+	if (!ttm->pages) {
 		ttm_tt_destroy(ttm);
 		pr_err("Failed allocating page table\n");
 		return -ENOMEM;
@@ -243,7 +246,7 @@ void ttm_dma_tt_fini(struct ttm_dma_tt *ttm_dma)
 
 	drm_free_large(ttm->pages);
 	ttm->pages = NULL;
-	drm_free_large(ttm_dma->dma_address);
+	ttm_dma->cpu_address = NULL;
 	ttm_dma->dma_address = NULL;
 }
 EXPORT_SYMBOL(ttm_dma_tt_fini);

include/drm/ttm/ttm_bo_driver.h

@@ -133,6 +133,7 @@ struct ttm_tt {
  * struct ttm_dma_tt
  *
  * @ttm: Base ttm_tt struct.
+ * @cpu_address: The CPU address of the pages
  * @dma_address: The DMA (bus) addresses of the pages
  * @pages_list: used by some page allocation backend
  *
@@ -142,6 +143,7 @@ struct ttm_tt {
  */
 struct ttm_dma_tt {
 	struct ttm_tt ttm;
+	void **cpu_address;
 	dma_addr_t *dma_address;
 	struct list_head pages_list;
 };