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| author | Bin Meng <bmeng.cn@gmail.com> | 2015-10-23 02:13:32 (GMT) |
|---|---|---|
| committer | Bin Meng <bmeng.cn@gmail.com> | 2015-11-13 14:46:20 (GMT) |
| commit | e5ffa4bb62b4532079ea552a804178f3955775f9 (patch) | |
| tree | f2729cf1115d2d4c13adf3242520504b44f4b4c6 /arch/x86/cpu | |
| parent | 1eb39a509354ae3c199c739bfb2d3a0d442e2cac (diff) | |
| download | u-boot-e5ffa4bb62b4532079ea552a804178f3955775f9.tar.xz | |
x86: queensbay: Really disable IGD
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>
Diffstat (limited to 'arch/x86/cpu')
| -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 0c02a44..933d189 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) |