nvkm_wrvgas
void nvkm_wrvgas(struct nvkm_device *, int head, u8 index, u8 value);
if (port == 0x03c4) nvkm_wrvgas(device, head, index, value);
nvkm_wrvgas(device, 0, 1, nvkm_rdvgas(device, 0, 1) & ~0x20);
nvkm_wrvgas(device, 0, 1, nvkm_rdvgas(device, 0, 1) | 0x20);
nvkm_wrvgas(device, 0, 1, nvkm_rdvgas(device, 0, 1) & ~0x20);
nvkm_wrvgas(device, 0, 1, nvkm_rdvgas(device, 0, 1) | 0x20);