struct nvkm_device *device = gr->base.engine.subdev.device;
 
        nvkm_wr32(device, 0x409804, 0xffffffff);
-       nvkm_wr32(device, 0x409840, 0xffffffff);
+       nvkm_wr32(device, 0x409800, 0x00000000);
        nvkm_wr32(device, 0x409500, 0xffffffff);
        nvkm_wr32(device, 0x409504, mthd);
        nvkm_msec(device, 2000,
 {
        struct nvkm_device *device = gr->base.engine.subdev.device;
 
-       nvkm_wr32(device, 0x409840, 0x00000030);
+       nvkm_mask(device, 0x409800, 0x00000030, 0x00000000);
        nvkm_wr32(device, 0x409500, inst);
        nvkm_wr32(device, 0x409504, 0x00000003);
        nvkm_msec(device, 2000,
 {
        struct nvkm_device *device = gr->base.engine.subdev.device;
 
-       nvkm_wr32(device, 0x409840, 0xffffffff);
+       nvkm_wr32(device, 0x409800, 0x00000000);
        nvkm_wr32(device, 0x409500, 0x00000000);
        nvkm_wr32(device, 0x409504, 0x00000025);
        nvkm_msec(device, 2000,
 {
        struct nvkm_device *device = gr->base.engine.subdev.device;
 
-       nvkm_wr32(device, 0x409840, 0xffffffff);
+       nvkm_wr32(device, 0x409800, 0x00000000);
        nvkm_wr32(device, 0x409500, 0x00000000);
        nvkm_wr32(device, 0x409504, 0x00000016);
        nvkm_msec(device, 2000,
 {
        struct nvkm_device *device = gr->base.engine.subdev.device;
 
-       nvkm_wr32(device, 0x409840, 0xffffffff);
+       nvkm_wr32(device, 0x409800, 0x00000000);
        nvkm_wr32(device, 0x409500, 0x00000000);
        nvkm_wr32(device, 0x409504, 0x00000010);
        nvkm_msec(device, 2000,
 {
        struct nvkm_device *device = gr->base.engine.subdev.device;
 
-       nvkm_wr32(device, 0x409840, 0xffffffff);
+       nvkm_wr32(device, 0x409800, 0x00000000);
        nvkm_wr32(device, 0x409500, timeout);
        nvkm_wr32(device, 0x409504, 0x00000021);
 }
        nvkm_mc_unk260(device, 1);
 
        /* start both of them running */
-       nvkm_wr32(device, 0x409840, 0xffffffff);
+       nvkm_wr32(device, 0x409800, 0x00000000);
        nvkm_wr32(device, 0x41a10c, 0x00000000);
        nvkm_wr32(device, 0x40910c, 0x00000000);