mirror of
https://github.com/torvalds/linux.git
synced 2024-11-24 05:02:12 +00:00
5616c23ad9
The boot protocol, USB legacy support, and zero-page documentation is common to the x86 platform, not i386-specific. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
45 lines
1.8 KiB
Plaintext
45 lines
1.8 KiB
Plaintext
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.
|
|
|