[lm-sensors] Super I/O chip: missing VID base address

[lm-sensors] Super I/O chip: missing VID base address

[Lutz Ballaschke]

Hi there,

i have to program parts of the super I/O chip F71862 from Fintek on a
Jetway J7F2 x86 mini-ITX board. There is an existing linux driver
(f71882fg) which supports the hardware monitoring function of that chip
(FAN, TEMP, PWM) but not the VID function. 
So i started coding to get this VID function working. Unfortunately i
got disappointed the moment i tried to read the base address out of the
VID configuration register: the value is 

0x00 

which i suppose is not the actual IO address, is it? Confused by the
datasheet telling the same i wondered if that means i can't use VID
function or just have to find out the default base address (like 0x3F8
is default for UART which is also part of the F71862 chip)
Any idea?

Thank you very much,

Lutz Ballaschke


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Re: [lm-sensors] Super I/O chip: missing VID base address

[Jean Delvare]

Hallo Lutz,

On Wed, 17 Feb 2010 18:35:21 +0100, Lutz Ballaschke wrote:
> Hi there,
> 
> i have to program parts of the super I/O chip F71862 from Fintek on a
> Jetway J7F2 x86 mini-ITX board. There is an existing linux driver
> (f71882fg) which supports the hardware monitoring function of that chip
> (FAN, TEMP, PWM) but not the VID function. 

Correct. Looking at the datasheet, I am not surprised... The VID
controller has only 4 input pins, while all recent CPU models need 6, 7
of even 8. I have no idea why Fintek did this, but in practice this
makes the VID feature of the F71862 essentially useless.

> So i started coding to get this VID function working. Unfortunately i
> got disappointed the moment i tried to read the base address out of the
> VID configuration register: the value is 
> 
> 0x00 
> 
> which i suppose is not the actual IO address, is it? Confused by the
> datasheet telling the same i wondered if that means i can't use VID
> function or just have to find out the default base address (like 0x3F8
> is default for UART which is also part of the F71862 chip)
> Any idea?

The base I/O of each logical device must be set by the BIOS prior to
use. Some logical devices may have a default value but the VID one does
not. If the BIOS did not set any address, you have to do it before
enabling the logical device (setting bit 0 of register 0x30 to 1.) You
are free to set the address to whatever you want, but I would suggest
picking a multiple of at least 16, and making sure you won't hit
already used ports (check in /proc/ioports.)

Then again, I am not sure how the VID feature of this chip would be
used on a recent system.

-- 
Jean Delvare
http://khali.linux-fr.org/wishlist.html

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