drm/ttm: Merge hugepage attr changes in ttm_dma_page_put. (v2)

Every set_pages_array_wb call resulted in cross-core
interrupts and TLB flushes. Merge more of them for
less overhead.

This reduces the time needed to free a 1.6 GiB GTT WC
buffer as part of Vulkan CTS from  ~2 sec to < 0.25 sec.
(Allocation still takes more than 2 sec though)

(v2): use set_pages_wb instead of set_memory_wb.

Signed-off-by: Bas Nieuwenhuizen <basni@chromium.org>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/ttm/ttm_page_alloc_dma.c

@@ -349,17 +349,14 @@ static void ttm_pool_update_free_locked(struct dma_pool *pool,
 static void ttm_dma_page_put(struct dma_pool *pool, struct dma_page *d_page)
 {
 	struct page *page = d_page->p;
-	unsigned i, num_pages;
+	unsigned num_pages;
 
 	/* Don't set WB on WB page pool. */
 	if (!(pool->type & IS_CACHED)) {
 		num_pages = pool->size / PAGE_SIZE;
-		for (i = 0; i < num_pages; ++i, ++page) {
-			if (ttm_set_pages_array_wb(&page, 1)) {
-				pr_err("%s: Failed to set %d pages to wb!\n",
-				       pool->dev_name, 1);
-			}
-		}
+		if (ttm_set_pages_wb(page, num_pages))
+			pr_err("%s: Failed to set %d pages to wb!\n",
+			       pool->dev_name, num_pages);
 	}
 
 	list_del(&d_page->page_list);