Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | USB Legacy support |
2 | ~~~~~~~~~~~~~~~~~~ | |
3 | ||
4 | Vojtech Pavlik <vojtech@suse.cz>, January 2004 | |
5 | ||
6 | ||
7 | Also known as "USB Keyboard" or "USB Mouse support" in the BIOS Setup is a | |
8 | feature that allows one to use the USB mouse and keyboard as if they were | |
9 | their classic PS/2 counterparts. This means one can use an USB keyboard to | |
10 | type in LILO for example. | |
11 | ||
12 | It has several drawbacks, though: | |
13 | ||
14 | 1) On some machines, the emulated PS/2 mouse takes over even when no USB | |
15 | mouse is present and a real PS/2 mouse is present. In that case the extra | |
16 | features (wheel, extra buttons, touchpad mode) of the real PS/2 mouse may | |
17 | not be available. | |
18 | ||
19 | 2) If CONFIG_HIGHMEM64G is enabled, the PS/2 mouse emulation can cause | |
20 | system crashes, because the SMM BIOS is not expecting to be in PAE mode. | |
21 | The Intel E7505 is a typical machine where this happens. | |
22 | ||
23 | 3) If AMD64 64-bit mode is enabled, again system crashes often happen, | |
24 | because the SMM BIOS isn't expecting the CPU to be in 64-bit mode. The | |
25 | BIOS manufacturers only test with Windows, and Windows doesn't do 64-bit | |
26 | yet. | |
27 | ||
28 | Solutions: | |
29 | ||
30 | Problem 1) can be solved by loading the USB drivers prior to loading the | |
31 | PS/2 mouse driver. Since the PS/2 mouse driver is in 2.6 compiled into | |
32 | the kernel unconditionally, this means the USB drivers need to be | |
33 | compiled-in, too. | |
34 | ||
35 | Problem 2) can currently only be solved by either disabling HIGHMEM64G | |
36 | in the kernel config or USB Legacy support in the BIOS. A BIOS update | |
37 | could help, but so far no such update exists. | |
38 | ||
39 | Problem 3) is usually fixed by a BIOS update. Check the board | |
40 | manufacturers web site. If an update is not available, disable USB | |
41 | Legacy support in the BIOS. If this alone doesn't help, try also adding | |
42 | idle=poll on the kernel command line. The BIOS may be entering the SMM | |
43 | on the HLT instruction as well. | |
44 |