drm/nvc0: implement irq handler for whatever's at 0x14xxxx

This is just barely enough to stop a never-ending IRQ storm that can
be triggered by our 3D driver.  We have no idea what this engine is..
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvc0_graph.c

@@ -31,6 +31,7 @@
 #include "nvc0_graph.h"
 
 static void nvc0_graph_isr(struct drm_device *);
+static void nvc0_runk140_isr(struct drm_device *);
 static int  nvc0_graph_unload_context_to(struct drm_device *dev, u64 chan);
 
 void
@@ -281,6 +282,7 @@ nvc0_graph_destroy(struct drm_device *dev)
 		return;
 
 	nouveau_irq_unregister(dev, 12);
+	nouveau_irq_unregister(dev, 25);
 
 	nouveau_gpuobj_ref(NULL, &priv->unk4188b8);
 	nouveau_gpuobj_ref(NULL, &priv->unk4188b4);
@@ -390,6 +392,7 @@ nvc0_graph_create(struct drm_device *dev)
 	}
 
 	nouveau_irq_register(dev, 12, nvc0_graph_isr);
+	nouveau_irq_register(dev, 25, nvc0_runk140_isr);
 	NVOBJ_CLASS(dev, 0x902d, GR); /* 2D */
 	NVOBJ_CLASS(dev, 0x9039, GR); /* M2MF */
 	NVOBJ_CLASS(dev, 0x9097, GR); /* 3D */
@@ -777,3 +780,19 @@ nvc0_graph_isr(struct drm_device *dev)
 
 	nv_wr32(dev, 0x400500, 0x00010001);
 }
+
+static void
+nvc0_runk140_isr(struct drm_device *dev)
+{
+	u32 units = nv_rd32(dev, 0x00017c) & 0x1f;
+
+	while (units) {
+		u32 unit = ffs(units) - 1;
+		u32 reg = 0x140000 + unit * 0x2000;
+		u32 st0 = nv_mask(dev, reg + 0x1020, 0, 0);
+		u32 st1 = nv_mask(dev, reg + 0x1420, 0, 0);
+
+		NV_INFO(dev, "PRUNK140: %d 0x%08x 0x%08x\n", unit, st0, st1);
+		units &= ~(1 << unit);
+	}
+}