support of SMBus on ICH3

[Igor Pokrovsky]

On Tue, Aug 12, 2003 at 04:54:09PM +0200, Stijn Hoop wrote:
> > So, 0 and 3 bits are set by default? Right?
> > What prevents us from detecting SMBus then?
> 
> The fact that those bits are set by default on boot. From the manual:
> 
> bit	name		
> 3	D31_F3_Disable
> 	R/W. Software sets this bit to disable the SMBus Host Controller
> 	function. BIOS must not enable I/O or memory address space decode,
> 	interrupt generation, or any other functionality of functions that
> 	are to be disabled.
> 		0 = SMBus controller is enabled.
> 		1 = SMBus controller is disabled.
> 
> 0	SMB_FOR_BIOS
> 	R/W. This bit is used in conjunction with bit 3 in this register.
> 		0 = No effect.
> 		1 = Allows the SMBus I/O space to be accessible by software
> 		    when bit 3 in this register is set. The PCI configuration
> 		    space is hidden in this case. Note that if bit 3 is set
> 		    alone, the decode of both SMBus PCI configuration and I/O
> 		    space will be disabled.
> 
> Both bits are set, so 'the SMBus I/O space' is accessible (whatever that
> means).
Yeah, you right, seems to me I'm too tired. I read this and was under impression
that if the bit is set - everything is enabled :-)

> I suspect Don is right, and the motherboard disables the SMBus controller
> becase there are no slave devices wired to it. Dell (the brand of my
> laptop) uses ACPI and a proprietary method to determine thermal values,
> so they must have disabled SMBus to avoid implementing yet another
> way to read those.
How did you know that? In fact I need SMBus only for the reason to
run sysutils/wmhm. It is very important for me when it is about
+40C around here. And laptop just turns off automatically without
any warning. And want to monitor processor temperature in order not
to loose my work.

> If there was an ichsmb kernel module, you could theoretically clear
> the above bits, and _then_ load the module -- it should attach.
> I didn't see any method through adding quirks to always do this on boot
> though.

-ip

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