drm/nouveau/fifo/g84-: ack non-stall interrupt before handling it

Closes a very unlikely race that can occur if another NonStallInterrupt
method passes between checking fences and acking the previous interrupt.

With this change, the interrupt will re-fire under such conditions.
Tested-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/engine/fifo/nv04.c

@@ -551,8 +551,8 @@ nv04_fifo_intr(struct nouveau_subdev *subdev)
 			}
 
 			if (status & 0x40000000) {
-				nouveau_fifo_uevent(&priv->base);
 				nv_wr32(priv, 0x002100, 0x40000000);
+				nouveau_fifo_uevent(&priv->base);
 				status &= ~0x40000000;
 			}
 		}

drivers/gpu/drm/nouveau/core/engine/fifo/nvc0.c

@@ -740,6 +740,8 @@ nvc0_fifo_intr_engine_unit(struct nvc0_fifo_priv *priv, int engn)
 	u32 inte = nv_rd32(priv, 0x002628);
 	u32 unkn;
 
+	nv_wr32(priv, 0x0025a8 + (engn * 0x04), intr);
+
 	for (unkn = 0; unkn < 8; unkn++) {
 		u32 ints = (intr >> (unkn * 0x04)) & inte;
 		if (ints & 0x1) {
@@ -751,8 +753,6 @@ nvc0_fifo_intr_engine_unit(struct nvc0_fifo_priv *priv, int engn)
 			nv_mask(priv, 0x002628, ints, 0);
 		}
 	}
-
-	nv_wr32(priv, 0x0025a8 + (engn * 0x04), intr);
 }
 
 static void

drivers/gpu/drm/nouveau/core/engine/fifo/nve0.c

@@ -952,8 +952,8 @@ nve0_fifo_intr(struct nouveau_subdev *subdev)
 	}
 
 	if (stat & 0x80000000) {
-		nve0_fifo_intr_engine(priv);
 		nv_wr32(priv, 0x002100, 0x80000000);
+		nve0_fifo_intr_engine(priv);
 		stat &= ~0x80000000;
 	}