i386/166784: VIA 6420 SATA150 not AHCI-capable?

[Martin Beach]

>Number:         166784
>Category:       i386
>Synopsis:       VIA 6420 SATA150 not AHCI-capable?
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-i386
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Apr 09 08:40:11 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Martin Beach
>Release:        9.0-RELEASE FreeBSD
>Organization:
-
>Environment:
>Description:
I noticed that pure ahci is not possible with my VIA CN700 based board.
The controller used is a 

atapci0: <VIA 6420 SATA150 controller> port 0xfe00-0xfe07,0xfd00-0xfd03,0xfc00-0xfc07,0xfb00-0xfb03,0xfa00-0xfa0f,0xee00-0xeeff irq 20 at device 15.0 on pci0

However AHCI with ATA_CAM does not work. I have to use 'ata' additionally in the kernel to have access to my disk.
The device nodes used for the partitions are all prefixed with ada*.
lrwxr-xr-x  1 root  wheel            6 Apr  9 10:21 /dev/ad4s1 -> ada0s1
lrwxr-xr-x  1 root  wheel            7 Apr  9 10:21 /dev/ad4s1a -> ada0s1a
lrwxr-xr-x  1 root  wheel            7 Apr  9 10:21 /dev/ad4s1b -> ada0s1b
lrwxr-xr-x  1 root  wheel            7 Apr  9 10:21 /dev/ad4s1d -> ada0s1d
lrwxr-xr-x  1 root  wheel            7 Apr  9 10:21 /dev/ad4s1e -> ada0s1e
lrwxr-xr-x  1 root  wheel            7 Apr  9 10:21 /dev/ad4s1f -> ada0s1f

When compiling the kernel without 'device ata' and just leaving 'device ahci and options ATA_CAM' it does not work.

Bug or feature?
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: