[ltp] Thinkpad X30, 2.6.21-rc5, and the hdaps module.

[Andrew J. Barr]

Steve Thompson wrote:
  > A bug seems likely.  As I have time I will isolate the invariants of 
this
> problem, but I don't reboot the machine all that much so it will take a
> little time to isolate exactly who is doing what to whom.  I am somewhat
> curious as to why the BIOS can set the CPU down to as low as 200MHz with
> linux thinking it can step the processer up and down at entirely different
> rates.  It just seems odd.

There are two different things, I believe, that determine the processor 
clock speed.

I think the 200MHz frequency (and anything below 600MHz) that Windows 
(and evidently the BIOS) reports is the result of SpeedStep + processor 
C-states. This is at least the case for the Pentium-M in my R51. You 
will see this number if you use gkrellm-x86info, for instance.

> You're perfectly correct, of course.  Arbitrary ports may reset counters
> or trigger actions and arbitrary events when read.  Of course, it is
> usually the case that initiating a primary device function requires an IO
> port write.  Sure, there's lots of buggy hardware (and people, if you
> believe the stories about aliens) out there that will jump right off into
> the hardware equivalent of undefined behaviour when probed
> indiscriminately.
> 
> Arbitrarily reading IO ports associated with a network or SCSI controller
> -- especially behind the back of the OS --  can be particularly bad.  But
> if one looks at /proc/ioports and makes sure he is not bashing on
> something already installed and not associated with the device under test,
> then there is not too much risk -- particularly if you do it on a quite
> system immediately after a `sync`.

I think there is the (very real) possibility for actual hardware damage 
on the Thinkpad. Read some of the discussions a few months back about 
tp_smapi and hdaps.

Andrew