+ /*
+ * According to Atom E6xx datasheet, setting VGA Disable (bit17)
+ * of Graphics Controller register (offset 0x50) prevents IGD
+ * (D2:F0) from reporting itself as a VGA display controller
+ * class in the PCI configuration space, and should also prevent
+ * it from responding to VGA legacy memory range and I/O addresses.
+ *
+ * However test result shows that with just VGA Disable bit set and
+ * a PCIe graphics card connected to one of the PCIe controllers on
+ * the E6xx, accessing the VGA legacy space still causes system hang.
+ * After a number of attempts, it turns out besides VGA Disable bit,
+ * the SDVO (D3:F0) device should be disabled to make it work.
+ *
+ * To simplify, use the Function Disable register (offset 0xc4)
+ * to disable both IGD (D2:F0) and SDVO (D3:F0) devices. Now these
+ * two devices will be completely disabled (invisible in the PCI
+ * configuration space) unless a system reset is performed.
+ */
+ dm_pci_write_config32(igd, IGD_FD, FUNC_DISABLE);
+ dm_pci_write_config32(sdvo, IGD_FD, FUNC_DISABLE);