diff options
Diffstat (limited to 'arch/x86/cpu/queensbay/tnc.c')
| -rw-r--r-- | arch/x86/cpu/queensbay/tnc.c | 26 |
1 files changed, 20 insertions, 6 deletions
diff --git a/arch/x86/cpu/queensbay/tnc.c b/arch/x86/cpu/queensbay/tnc.c index 0c02a44f63..933d189f05 100644 --- a/arch/x86/cpu/queensbay/tnc.c +++ b/arch/x86/cpu/queensbay/tnc.c @@ -25,12 +25,26 @@ static void unprotect_spi_flash(void) static void __maybe_unused disable_igd(void) { - u32 gc; - - gc = x86_pci_read_config32(TNC_IGD, IGD_GC); - gc &= ~GMS_MASK; - gc |= VGA_DISABLE; - x86_pci_write_config32(TNC_IGD, IGD_GC, gc); + /* + * 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. + */ + x86_pci_write_config32(TNC_IGD, IGD_FD, FUNC_DISABLE); + x86_pci_write_config32(TNC_SDVO, IGD_FD, FUNC_DISABLE); } int arch_cpu_init(void) |
