drm/nouveau/disp: add supervisor mutex

Will be used to protect NVIF_CLASS_OUTP method calls from racing with
in-progress supervisor handling.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/nouveau/include/nvkm/engine/disp.h

@@ -22,6 +22,7 @@ struct nvkm_disp {
 		struct workqueue_struct *wq;
 		struct work_struct work;
 		u32 pending;
+		struct mutex mutex;
 	} super;
 
 #define NVKM_DISP_EVENT_CHAN_AWAKEN BIT(0)

drivers/gpu/drm/nouveau/nvkm/engine/disp/base.c

@@ -399,8 +399,11 @@ nvkm_disp_dtor(struct nvkm_engine *engine)
 	nvkm_gpuobj_del(&disp->inst);
 
 	nvkm_event_fini(&disp->uevent);
-	if (disp->super.wq)
+
+	if (disp->super.wq) {
 		destroy_workqueue(disp->super.wq);
+		mutex_destroy(&disp->super.mutex);
+	}
 
 	nvkm_event_fini(&disp->vblank);
 	nvkm_event_fini(&disp->hpd);
@@ -467,6 +470,7 @@ nvkm_disp_new_(const struct nvkm_disp_func *func, struct nvkm_device *device,
 			return -ENOMEM;
 
 		INIT_WORK(&disp->super.work, func->super);
+		mutex_init(&disp->super.mutex);
 	}
 
 	return nvkm_event_init(func->uevent, 1, ARRAY_SIZE(disp->chan), &disp->uevent);

drivers/gpu/drm/nouveau/nvkm/engine/disp/gf119.c

@@ -995,6 +995,8 @@ gf119_disp_super(struct work_struct *work)
 	u32 mask[4];
 
 	nvkm_debug(subdev, "supervisor %d\n", ffs(disp->super.pending));
+	mutex_lock(&disp->super.mutex);
+
 	list_for_each_entry(head, &disp->heads, head) {
 		mask[head->id] = nvkm_rd32(device, 0x6101d4 + (head->id * 0x800));
 		HEAD_DBG(head, "%08x", mask[head->id]);
@@ -1037,7 +1039,9 @@ gf119_disp_super(struct work_struct *work)
 
 	list_for_each_entry(head, &disp->heads, head)
 		nvkm_wr32(device, 0x6101d4 + (head->id * 0x800), 0x00000000);
+
 	nvkm_wr32(device, 0x6101d0, 0x80000000);
+	mutex_unlock(&disp->super.mutex);
 }
 
 void

drivers/gpu/drm/nouveau/nvkm/engine/disp/gv100.c

@@ -818,8 +818,10 @@ gv100_disp_super(struct work_struct *work)
 	struct nvkm_subdev *subdev = &disp->engine.subdev;
 	struct nvkm_device *device = subdev->device;
 	struct nvkm_head *head;
-	u32 stat = nvkm_rd32(device, 0x6107a8);
-	u32 mask[4];
+	u32 stat, mask[4];
+
+	mutex_lock(&disp->super.mutex);
+	stat = nvkm_rd32(device, 0x6107a8);
 
 	nvkm_debug(subdev, "supervisor %d: %08x\n", ffs(disp->super.pending), stat);
 	list_for_each_entry(head, &disp->heads, head) {
@@ -864,7 +866,9 @@ gv100_disp_super(struct work_struct *work)
 
 	list_for_each_entry(head, &disp->heads, head)
 		nvkm_wr32(device, 0x6107ac + (head->id * 4), 0x00000000);
+
 	nvkm_wr32(device, 0x6107a8, 0x80000000);
+	mutex_unlock(&disp->super.mutex);
 }
 
 static void

drivers/gpu/drm/nouveau/nvkm/engine/disp/nv50.c

@@ -1345,7 +1345,10 @@ nv50_disp_super(struct work_struct *work)
 	struct nvkm_subdev *subdev = &disp->engine.subdev;
 	struct nvkm_device *device = subdev->device;
 	struct nvkm_head *head;
-	u32 super = nvkm_rd32(device, 0x610030);
+	u32 super;
+
+	mutex_lock(&disp->super.mutex);
+	super = nvkm_rd32(device, 0x610030);
 
 	nvkm_debug(subdev, "supervisor %08x %08x\n", disp->super.pending, super);
 
@@ -1387,6 +1390,7 @@ nv50_disp_super(struct work_struct *work)
 	}
 
 	nvkm_wr32(device, 0x610030, 0x80000000);
+	mutex_unlock(&disp->super.mutex);
 }
 
 const struct nvkm_enum