http://bugzilla.kernel.org/show_bug.cgi?id=8850
------- Comment #24 from [EMAIL PROTECTED] 2007-10-11 19:41 -------
Well, I'm not sure if we are in the right direction.:(
First, your original DSDT shows that FAN device has empty _PS0, _PS3 method,
usually this means that the fan is controlled by BIOS.
I found that power resource device PFAN is not referenced by any device, and it
may be used for fan power control, so I did some hack in your DSDT.
And the test results show that PFAN can be used to control FAN state.
This is a good news, but we still have one problem.
Here is the _STA method of power resource file PFAN.
Method (_STA, 0, NotSerialized)
{
And (\_SB.PCI0.PIB.PMRD (0xFF), 0x04, Local7)
ShiftRight (Local7, 0x01, Local7)
Return (Local7)
}
_STA should return 0/1 according to the ACPI spec, where "0" means power
resource is off and "1" means power resource is on.
We can see that the _STA method in your DSDT always return 0 or 2. thus we are
always told that power resouce/fan is off because the bit 0 of _STA return
value is always 0. So this is apparentlly a BIOS bug.
The problem is that we don't know which bit of \_SB.PCI0.PIB.PMRD(0xFF) stands
for the status of power resource PFAN. I tried to change ShiftRight (Local7,
0x01, Local7) to ShiftRight (Local7, 0x02, Local7) in comment #22 but without
any luck.
Now we need to find out which bit stands for PFAN status. But all these efforts
only make sense only if the mother board vendor really wants PFAN to
control fan device.
But one thing strange is that you said "MS Windows slows down the fan when CPU
is cool and speeds it up when CPU is busy."
Now this is also true for Linux after overriding the DSDT except that it starts
spinning too often, right? :)
Maybe you can override the active trip point by adding a boot parameter
thermal.act=xxx, here xxx is the temperature you want the fan starts to spin.
BTW: for the wrong buggy _STA issue: this only confuses the user who want to
get the fan state. but let's debug further to see if we can make ACPI work
perfectly on this machine. :)
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