BUSY_SLOT
status->busy = nvkm_falcon_rd32(falcon, 0x508 + (BUSY_SLOT * 0x10));
nvkm_falcon_wr32(falcon, 0x508 + (BUSY_SLOT * 0x10), 0x80000000);
nvkm_falcon_wr32(falcon, 0x504 + (BUSY_SLOT * 0x10), 0x00200001);
nvkm_falcon_wr32(falcon, 0x50c + (BUSY_SLOT * 0x10), 0x00000002);