DMA disabled after lost interrupt (on ibook)

[vivenzio <vivenzio@web.de>]

Hi people,

occasionally, I get "lost interrupt" messages in the logs of my ibook.

They typically show up when the hard disc drive is busy,
e.g. when lots of packages are extracted during "apt-get upgrade".

When this happens, the hard disc "stops" working for some
seconds and then continues to work.

The following messages are logged by the kernel, then:

  kernel: ide-pmac lost interrupt, dma status: 8400
  kernel: hda: lost interrupt
  kernel: hda: dma_intr: status=0xd0 { Busy }
  kernel:
  kernel: ide: failed opcode was: unknown
  kernel: hda: DMA disabled
  kernel: ide0: reset: success

After issuing "hdparm -d1 /dev/hda", DMA is enabled again
and remains enabled, at least if the drive is not too
busy at that time. If all goes well, the kernel says:

  kernel: hda: Enabling Ultra DMA 5

Some information on my ibook G4 (14' 933MHz model):
- My /proc/cpuinfo says:
processor       : 0
cpu             : 7455, altivec supported
clock           : 707MHz
revision        : 0.3 (pvr 8001 0303)
bogomips        : 710.65
machine         : PowerBook6,3
motherboard     : PowerBook6,3 MacRISC3 Power Macintosh
detected as     : 287 (iBook G4)
pmac flags      : 0000001b
L2 cache        : 256K unified
memory          : 640MB
pmac-generation : NewWorld

Kernel version is 2.6.12.1 (but I noticed the "lost interrupt"
messages already with previous 2.6 versions).

If more information is necessary (Kernel config?), just tell me.

If this could be some HW problem, how can I test if this really
happens due to HW faults or because of a problem in the Linux kernel?
(Maybe I can figure this out with MacOSX? But how?)

Thanks for any help,
Vivenzio