diff --git a/drivers/gpu/drm/nouveau/nouveau_agp.c b/drivers/gpu/drm/nouveau/nouveau_agp.c
index d28430cd2ba6..6e7a55f93a85 100644
--- a/drivers/gpu/drm/nouveau/nouveau_agp.c
+++ b/drivers/gpu/drm/nouveau/nouveau_agp.c
@@ -47,6 +47,18 @@ nouveau_agp_enabled(struct nouveau_drm *drm)
 	if (drm->agp.stat == UNKNOWN) {
 		if (!nouveau_agpmode)
 			return false;
+#ifdef __powerpc__
+		/* Disable AGP by default on all PowerPC machines for
+		 * now -- At least some UniNorth-2 AGP bridges are
+		 * known to be broken: DMA from the host to the card
+		 * works just fine, but writeback from the card to the
+		 * host goes straight to memory untranslated bypassing
+		 * the GATT somehow, making them quite painful to deal
+		 * with...
+		 */
+		if (nouveau_agpmode == -1)
+			return false;
+#endif
 		return true;
 	}