misc/130794: hw.ata.ata_dma_limit without any effect

[Daniel Tourde]

>Number:         130794
>Category:       misc
>Synopsis:       hw.ata.ata_dma_limit without any effect
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jan 20 21:50:03 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Daniel Tourde
>Release:        7.1
>Organization:
>Environment:
FreeBSD 7.1-RELEASE #0 GENERIC amd64
>Description:
Hi!

I need to slow down the UDMA on my Hard Drive. It is set automatically to UDMA133 which causes a lot of warnings and if I bring it to UDMA100, the warning and the error messages disappear.

To do so, 2 options:
- The inelegant: atacontrol mode ad0 UDMA5
- The elegant: put hw.ata.ata_dma_limit="5" in loader.conf

I am very tempted by the elegant solution but unfortunately it does not work. It has absolutely no effect whatsoever... :(

sysctl hw.ata.ata_dma_limit="5" gives
sysctl: unknown oid 'hw.ata.ata_dma_limit'

I think it is a bug...

Daniel
>How-To-Repeat:

>Fix:


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