NV_PBUS_POWERCTRL_2
saved_powerctrl_2 = nvif_rd32(device, NV_PBUS_POWERCTRL_2);
nvif_wr32(device, NV_PBUS_POWERCTRL_2, saved_powerctrl_2 & 0xd7ffffff);
nvif_wr32(device, NV_PBUS_POWERCTRL_2, saved_powerctrl_2);
nvif_wr32(device, NV_PBUS_POWERCTRL_2, 0);
nvif_wr32(device, NV_PBUS_POWERCTRL_2, 0);