drm: ati_pcigart: Fix limit check in drm_ati_pcigart_init().

The variable 'max_pages' is ambiguous.  There are two concepts
of "pages" being used in this function.

First, we have ATI GART pages which are always 4096 bytes.
Then, we have system pages which are of size PAGE_SIZE.

Eliminate the confusion by creating max_ati_pages and
max_real_pages.  Calculate and use them as appropriate.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NDave Airlie <airlied@linux.ie>

drivers/gpu/drm/ati_pcigart.c

@@ -102,7 +102,7 @@ int drm_ati_pcigart_init(struct drm_device *dev, struct drm_ati_pcigart_info *ga
 	u32 *pci_gart, page_base, gart_idx;
 	dma_addr_t bus_address = 0;
 	int i, j, ret = 0;
-	int max_pages;
+	int max_ati_pages, max_real_pages;
 
 	if (!entry) {
 		DRM_ERROR("no scatter/gather memory!\n");
@@ -130,14 +130,15 @@ int drm_ati_pcigart_init(struct drm_device *dev, struct drm_ati_pcigart_info *ga
 
 	pci_gart = (u32 *) address;
 
-	max_pages = (gart_info->table_size / sizeof(u32));
-	pages = (entry->pages <= max_pages)
-	    ? entry->pages : max_pages;
+	max_ati_pages = (gart_info->table_size / sizeof(u32));
+	max_real_pages = max_ati_pages / (PAGE_SIZE / ATI_PCIGART_PAGE_SIZE);
+	pages = (entry->pages <= max_real_pages)
+	    ? entry->pages : max_real_pages;
 
 	if (gart_info->gart_table_location == DRM_ATI_GART_MAIN) {
-		memset(pci_gart, 0, max_pages * sizeof(u32));
+		memset(pci_gart, 0, max_ati_pages * sizeof(u32));
 	} else {
-		for (gart_idx = 0; gart_idx < max_pages; gart_idx++)
+		for (gart_idx = 0; gart_idx < max_ati_pages; gart_idx++)
 			DRM_WRITE32(map, gart_idx * sizeof(u32), 0);
 	}