[Bug 6920] HDIO_SET_DMA failed: Operation not permitted

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------- Additional Comments From mdz at ubuntu.com  2005-04-12 17:54 UTC -------
(In reply to comment #11)
> > The cause is not clear
> 
> I see I was a bit unclear earlier, so let me specify. I have a NForce 2
> motherboard with a SATA controller. It holds my hard drive sda, which is working
> just fine. What is failing, however, is my regular P-ATA CD-ROM, which is hda
> (so it's not the root disk). When I try to turn on DMA with hdparm I get the
> same error message as the person who originally filed the bug.

Is the CD-ROM on the same controller, or a different one?  If it's on a
different controller than the disk with the root filesystem, then the solution
is to remove all ide-* modules from /etc/modules.

> My Debian unstable installation had this exact same bug. The reason was that
> ide_cd module was loaded before the driver for NForce 2. This caused ide_cd to
> grab hda, set it to PIO, and not give control to the NForce driver. I fixed it
> by tweaking the module config scripts so that ide_cd gets loaded last.

Your /etc/modules file doesn't show the NForce 2 driver being loaded there, so
it is either being loaded by the initrd (if your root disk is attached to that
same controller), or by hotplug (if not).

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