DMA appears broken in 2.6.11 for Mac 7200

linuxppcdev at linuxppcdev at
Fri Mar 18 13:55:29 EST 2005

Ben Said:
> On Mon, 2005-03-14 at 03:51 +0000, linuxppcdev at wrote:
> > Just updated a couple of old Mac 7200 (601) boxen and ran into trouble with
> > the ide driver and a promise PDC20267 card. 
> > 
> > The very same drives and card work fine on a 9500 but hang on a 7200. If
> > I set the kernel arg ide=nodma I get in the dmesg:
> > ide_setup: ide=nodma : Prevented DMA
> > and the 7200 boots and runs fine.
> > 
> > Another suspect, the mace ethernet driver (which also appears to use DMA)
> > doesn't work on the 7200 with 2.6.11 but does with 2.4.28 and it works 
> > with 2.6.11 on the 9500.
> Interesting. Not sure what's up, though. Those old machines were known
> to have bugs relative to cache coherency... also check wetehr we are
> setting the cache line size properly in PCI devices. You can also try to
> disable use of PCI memory write & invalidate command in all devices.
Did some more testing on this. Built a 2.4.30-pre1 kernel from bk source.

DMA works fine booting 2.4.30

I compared the dmesg and lspci and I see no differences in the cache line

Is it possible that the ppc 601 kernel fixes aren't getting done properly
in 2.6??


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