ATA DMA status?

[Nathan Whitehorn]

Nick Withers wrote:
> Hi guys,
> 
> Sorry to hassle, but how's the ATA DMA stuff (original CFT:
> http://lists.freebsd.org/pipermail/freebsd-ppc/2008-September/003054.html and http://lists.freebsd.org/pipermail/freebsd-ppc/2008-October/003187.html, http://lists.freebsd.org/pipermail/freebsd-ppc/2008-October/003314.html, for instance) going?
> 
> According to
> http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/powerpc/powermac/ata_dbdma.c (I'm still clinging on to CVS :-)) the MFC's been behind for a while - does this indicate there're still big problems? I've only got the one G4 box on 7-STABLE and am somewhat reluctant to test anything too "alpha" on it...
> 
> If I were to test it out on 7-STABLE, though, do I still just need the
> http://people.freebsd.org/~nwhitehorn/apple-ata-dma.patch patch (it
> seems outdated, e.g., not including the changes from the latest rev
> (184429 / CVS 1.2) to ata_dbdma.c)? Is
> http://people.freebsd.org/~nwhitehorn/kauai.marcel.patch applicable?
> 
> Thanks very much all, I'm looking forward to having DMA!

I've held off on the MFC due to insufficient testing. I have at least 
one report (from Marcel) that it can cause problems with the CD drive on 
certain models of Mac Mini. There have also been some vague reports of 
poorly defined other problems, so I have been hesitant to declare the 
DMA code working. On the other hand, there are no really serious 
problems (e.g. data corruption) that I have heard about.

If you want to test on 7, you should just be able to grab the current 
revisions of powermac/ata* from -CURRENT and replace the 7.1 versions 
with them. If it causes problems, you can roll back to the old kernel, 
though please report them first. I'd also appreciate success reports -- 
if I get enough, I'll go ahead and MFC the changes.
-Nathan