drm/nv50: use "nv86" tlb flush method on everything except 0x50/0xac

It has been reported that this greatly improves (and possibly fixes
completely) the stability of NVA3+ chipsets.  In traces of my NVA8,
NVIDIA now appear to be doing this too.

The most recent traces of 0x50 and 0xac I could find don't show NVIDIA
checking PGRAPH status on these flushes, so for now, we won't either.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_drv.h

@@ -1190,7 +1190,7 @@ extern int  nv50_graph_load_context(struct nouveau_channel *);
 extern int  nv50_graph_unload_context(struct drm_device *);
 extern int  nv50_grctx_init(struct nouveau_grctx *);
 extern void nv50_graph_tlb_flush(struct drm_device *dev);
-extern void nv86_graph_tlb_flush(struct drm_device *dev);
+extern void nv84_graph_tlb_flush(struct drm_device *dev);
 extern struct nouveau_enum nv50_data_error_names[];
 
 /* nvc0_graph.c */

drivers/gpu/drm/nouveau/nouveau_state.c

@@ -376,15 +376,11 @@ static int nouveau_init_engine_ptrs(struct drm_device *dev)
 		engine->graph.destroy_context	= nv50_graph_destroy_context;
 		engine->graph.load_context	= nv50_graph_load_context;
 		engine->graph.unload_context	= nv50_graph_unload_context;
-		if (dev_priv->chipset != 0x86)
+		if (dev_priv->chipset == 0x50 ||
+		    dev_priv->chipset == 0xac)
 			engine->graph.tlb_flush	= nv50_graph_tlb_flush;
-		else {
-			/* from what i can see nvidia do this on every
-			 * pre-NVA3 board except NVAC, but, we've only
-			 * ever seen problems on NV86
-			 */
-			engine->graph.tlb_flush	= nv86_graph_tlb_flush;
-		}
+		else
+			engine->graph.tlb_flush	= nv84_graph_tlb_flush;
 		engine->fifo.channels		= 128;
 		engine->fifo.init		= nv50_fifo_init;
 		engine->fifo.takedown		= nv50_fifo_takedown;

drivers/gpu/drm/nouveau/nv50_graph.c

@@ -503,7 +503,7 @@ nv50_graph_tlb_flush(struct drm_device *dev)
 }
 
 void
-nv86_graph_tlb_flush(struct drm_device *dev)
+nv84_graph_tlb_flush(struct drm_device *dev)
 {
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	struct nouveau_timer_engine *ptimer = &dev_priv->engine.timer;