| 123456789101112131415161718192021222324252627282930313233343536373839404142434445 |
- 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.
|
