AGP_NVIDIA_2_GARTCTRL
temp = pci_read_config(sc->mc2_dev, AGP_NVIDIA_2_GARTCTRL, 4);
pci_write_config(sc->mc2_dev, AGP_NVIDIA_2_GARTCTRL, temp | 0x11, 4);
temp = pci_read_config(sc->mc2_dev, AGP_NVIDIA_2_GARTCTRL, 4);
pci_write_config(sc->mc2_dev, AGP_NVIDIA_2_GARTCTRL, temp & ~(0x11), 4);