AGP_INTEL_I820_RDCR
pci_write_config(dev, AGP_INTEL_I820_RDCR,
(pci_read_config(dev, AGP_INTEL_I820_RDCR, 1)
reg = pci_read_config(dev, AGP_INTEL_I820_RDCR, 1) & ~(1 << 1);
pci_write_config(dev, AGP_INTEL_I820_RDCR, reg, 1);