Call for testers: Apple ATA DMA

[Marius Strobl]

On Sat, Sep 27, 2008 at 01:33:55PM -0500, Nathan Whitehorn wrote:
> Peter Grehan wrote:
> >Hi Nathan,
> >
> > > If I can get positive reports from a few more people who were
> >>having trouble, I'll drop this in the tree.
> >
> > The imac's ata-4 is working solidly at UDMA-66. The difference in CPU 
> >usage and i/o with dd at 32k block size is stunning: 2MB/7% idle before, 
> >18MB/75% idle with your patch.
> 
> I guess DMA is a useful technology :)
> 
> Thanks for testing -- I've committed the patch. I'll revisit it when 
> Marcel tests it on Monday and it erases his hard drive...

I see two issues with acd(4) on sparc64, which, given that
I don't see them with either amd64 or i386 and that there
are no such reports for these archs, I suspect are endian-
bugs (which might be hidden with 32-bit machines though):
a) read-only drives are falsely reported as having write
   capabilities in dmesg (this is a rather old bug but so
   far this seemed to be a cosmetic problem only)
b) DMA is broken in that file content read is wrong except
   for "small" files; there's no data corruption when PIO
   mode is forced (this seem to be a recurring bug once
   again present in HEAD).

Do you guys see these problems also with powerpc?

Marius