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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. Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Acked-by: Simon Glass <sjg@chromium.org> |
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