kern/45890: piixpm autoconfigure not always probing correctly

[paul%whooppee.com@localhost]

>Number:         45890
>Category:       kern
>Synopsis:       piixpm autoconfigure not always probing correctly
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jan 30 15:10:00 +0000 2012
>Originator:     Paul Goyette
>Release:        NetBSD 5.99.59
>Organization:
-------------------------------------------------------------------------
| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:       |
| Customer Service | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com    |
| Network Engineer | 0786 F758 55DE 53BA 7731 | pgoyette at juniper.net |
| Kernel Developer |                          | pgoyette at netbsd.org  |
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>Environment:
        
        
System: quicky.whooppee.com 5.99.59 NetBSD 5.99.59 (WHOOPPEE (shared) 
2012-01-09 04:41:18) #8: Sun Jan  8 21:10:34 PST 2012  
paul%screamer.whooppee.com@localhost:/build/netbsd-local/obj/amd64/sys/arch/amd64/compile/WHOOPPEE
 amd64
Machine: amd64
>Description:
        Under 5.99.55, the piixpm i2c bus does not get autoconfigured.

        But under 5.99.59, with no other changes, it works correctly. 

        And then with 5.99.60 it fails again.  

        I will be investigating this PR and provide additional info, just
        wanted to make sure the problem doesn't get lost.
>How-To-Repeat:
        Under 5.99.55 and 5.99.60, I get

        # grep piix dmesg-5.99.55
        piixpm0 at pci0 dev 20 function 0
        piixpm0: vendor 0x1002 product 0x4385 (rev. 0x41)
        piixpm0: SMBus disabled

        On same machine with 5.99.59, I get

        #  grep piix dmesg-5.99.59
        piixpm0 at pci0 dev 20 function 0
        piixpm0: vendor 0x1002 product 0x4385 (rev. 0x41)
        iic0 at piixpm0: I2C bus

>Fix:
        

>Unformatted: