http://bugzilla.kernel.org/show_bug.cgi?id=8757





------- Comment #34 from [EMAIL PROTECTED]  2007-10-19 05:40 -------
Here is some data about HDAPS really work, that is ignored by the module in the
Linux kernel.

The thinkpad embedded controller is a Renesas H8S/2140 series chip.  There are
three communication channels to it, one which emulates the keyboard controller,
one that is the standard ACPI EC interface, and a third one that is used by
HDAPS, smart battery queries, and "application level" access to the EC (to be
used by IBM's ThinkVantage suite, most probably).

The Renesas EC serves these channels as *interrupts*.  It is all in the Renesas
documentation (which is public).  If IBM implemented the entire command
handling of one of the channels in the interrupt handler, that means a lot of
activity in that channel will interfere with the other activities of the EC. 
It will "hog the CPU" (in this case, the EC), if you will.  If they implemented
all three channels entirely inside the interrupt handlers... well, things will
be even worse :-)

So, if removing HDAPS is making a difference for you, that means the EC is
being overworked somehow by either ACPI or HDAPS modules (yes, it could be
either).

Please try the out-of-tree driver tp_smapi's version of HDAPS (google for
tp_smapi).  It is a damn great deal more intelligent on the way it talks to the
Renesas EC, so it is a lot nicer to the EC if something weird is happening.

I have a T43, and 2.6.22 with tp_smapi's HDAPS in full use does not cause any
trouble at all.  And the EC runs in interrupt mode just fine.


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