On 27/05/13 18:17, Guenter Roeck wrote:
On Mon, May 27, 2013 at 07:10:13AM +0200, Santi Villalba wrote:
Hi Guenter,
On 24/05/13 19:34, Guenter Roeck wrote:
On Fri, May 24, 2013 at 11:47:55AM +0200, Santi Villalba wrote:
This controller is giving people some trouble, as it is shipped in
more and more laptops [1] and the fans can become quite annoying in
these systems.
In the past it was said that the main problem was the lack of a
datasheet from ITE [2]. Recently there has been progress from the
coreboot projects getting the info for quanta firmware on IT8518
[3]. Can this particular file help with the lack of specs or it
depends on other factors?
http://review.coreboot.org/gitweb?p=coreboot.git;a=blob;f=src/ec/quanta/it8518/acpi/ec.asl;h=7549fa283da69b9b1fca8589b1fc7f59fd30f7a4;hb=7e568559634199668859b7c662aea7f6b41f3920
I may be missing something, but my understanding is that the chip
has an embedded microcontroller (EC) which handles the actual fan
control. While the chip data sheet describes the hardware accessible
to the EC, and the API between CPU and EC, it does not describe
the logical interface between the two. Problem is that this
interface is not well defined and depends on the microcode
running on the EC.
The file referenced above seems to provide that information for the
specific board and for the microcode running on the EC in that board
(which appears to be the referenced 'quanta' firmware). That does
not mean, however, that it would be the same for other boards,
including yours.
A second potential problem is that the ACPI data provided above suggests
that the EC may be controlled through ACPI, which means that ACPI most
likely reserves the memory space needed to access the controller.
If this is the case in your system, which is quite likely, your best
option would be an ACPI driver.
That was my fearsome first guess. So I will look around a bit more
to check if there is any spec available on the concrete EC firmware
running clevo machines. If I find it I will try the ACPI driver
route first.
I don't think you need the firmware spec if ACPI is used. All you need to do is
to decode the ACPI table, check which accessors it provides, and write a driver
using those accessors. [1] should help. I don't know much about ACPI, so I won't
be able to help much further.
Looking through coreboot, there are lots of laptops using embedded controllers,
and for most if not all of them the access methods used are different.
Guenter
[1] http://smackerelofopinion.blogspot.com/2009/10/dumping-acpi-tables-using-acpidump-and.html
This puts me in the right track, already looking at the ACPI table. Will
take time but I will get there.
Thanks again
Santi
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