drm/ttm: Add helper functions to populate/map in one call (v2)

These functions replace a section of common code found
in radeon/amdgpu drivers (and possibly others) as part
of the ttm_tt_*populate() callbacks.

v2: squash in fix for sw iommu from Tom

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/ttm/ttm_page_alloc.c

@@ -920,6 +920,47 @@ void ttm_pool_unpopulate(struct ttm_tt *ttm)
 }
 EXPORT_SYMBOL(ttm_pool_unpopulate);
 
+int ttm_populate_and_map_pages(struct device *dev, struct ttm_dma_tt *tt)
+{
+	unsigned i;
+	int r;
+
+	r = ttm_pool_populate(&tt->ttm);
+	if (r)
+		return r;
+
+	for (i = 0; i < tt->ttm.num_pages; i++) {
+		tt->dma_address[i] = dma_map_page(dev, tt->ttm.pages[i],
+						  0, PAGE_SIZE,
+						  DMA_BIDIRECTIONAL);
+		if (dma_mapping_error(dev, tt->dma_address[i])) {
+			while (i--) {
+				dma_unmap_page(dev, tt->dma_address[i],
+					       PAGE_SIZE, DMA_BIDIRECTIONAL);
+				tt->dma_address[i] = 0;
+			}
+			ttm_pool_unpopulate(&tt->ttm);
+			return -EFAULT;
+		}
+	}
+	return 0;
+}
+EXPORT_SYMBOL(ttm_populate_and_map_pages);
+
+void ttm_unmap_and_unpopulate_pages(struct device *dev, struct ttm_dma_tt *tt)
+{
+	unsigned i;
+	
+	for (i = 0; i < tt->ttm.num_pages; i++) {
+		if (tt->dma_address[i]) {
+			dma_unmap_page(dev, tt->dma_address[i],
+				       PAGE_SIZE, DMA_BIDIRECTIONAL);
+		}
+	}
+	ttm_pool_unpopulate(&tt->ttm);
+}
+EXPORT_SYMBOL(ttm_unmap_and_unpopulate_pages);
+
 int ttm_page_alloc_debugfs(struct seq_file *m, void *data)
 {
 	struct ttm_page_pool *p;