diff options
| author | Len Brown <len.brown@intel.com> | 2008-10-22 23:57:26 -0400 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2008-10-23 00:11:07 -0400 |
| commit | 057316cc6a5b521b332a1d7ccc871cd60c904c74 (patch) | |
| tree | 4333e608da237c73ff69b10878025cca96dcb4c8 /Documentation/x86/usb-legacy-support.txt | |
| parent | 3e2dab9a1c2deb03c311eb3f83466009147ed4d3 (diff) | |
| parent | 2515ddc6db8eb49a79f0fe5e67ff09ac7c81eab4 (diff) | |
Merge branch 'linus' into test
Conflicts:
MAINTAINERS
arch/x86/kernel/acpi/boot.c
arch/x86/kernel/acpi/sleep.c
drivers/acpi/Kconfig
drivers/pnp/Makefile
drivers/pnp/quirks.c
Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'Documentation/x86/usb-legacy-support.txt')
| -rw-r--r-- | Documentation/x86/usb-legacy-support.txt | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/Documentation/x86/usb-legacy-support.txt b/Documentation/x86/usb-legacy-support.txt new file mode 100644 index 00000000000..1894cdfc69d --- /dev/null +++ b/Documentation/x86/usb-legacy-support.txt @@ -0,0 +1,44 @@ +USB Legacy support +~~~~~~~~~~~~~~~~~~ + +Vojtech Pavlik <vojtech@suse.cz>, January 2004 + + +Also known as "USB Keyboard" or "USB Mouse support" in the BIOS Setup is a +feature that allows one to use the USB mouse and keyboard as if they were +their classic PS/2 counterparts. This means one can use an USB keyboard to +type in LILO for example. + +It has several drawbacks, though: + +1) On some machines, the emulated PS/2 mouse takes over even when no USB + mouse is present and a real PS/2 mouse is present. In that case the extra + features (wheel, extra buttons, touchpad mode) of the real PS/2 mouse may + not be available. + +2) If CONFIG_HIGHMEM64G is enabled, the PS/2 mouse emulation can cause + system crashes, because the SMM BIOS is not expecting to be in PAE mode. + The Intel E7505 is a typical machine where this happens. + +3) If AMD64 64-bit mode is enabled, again system crashes often happen, + because the SMM BIOS isn't expecting the CPU to be in 64-bit mode. The + BIOS manufacturers only test with Windows, and Windows doesn't do 64-bit + yet. + +Solutions: + +Problem 1) can be solved by loading the USB drivers prior to loading the +PS/2 mouse driver. Since the PS/2 mouse driver is in 2.6 compiled into +the kernel unconditionally, this means the USB drivers need to be +compiled-in, too. + +Problem 2) can currently only be solved by either disabling HIGHMEM64G +in the kernel config or USB Legacy support in the BIOS. A BIOS update +could help, but so far no such update exists. + +Problem 3) is usually fixed by a BIOS update. Check the board +manufacturers web site. If an update is not available, disable USB +Legacy support in the BIOS. If this alone doesn't help, try also adding +idle=poll on the kernel command line. The BIOS may be entering the SMM +on the HLT instruction as well. + |