[TriLUG] RH 7.1 DMA + IDE CDROM problem

[Benjamin Reed]

> The suggested workaround is to issue a hdparm -d 0 in rc.local
> I've done this but shortly after bootup (or giving command at console),
> somewhere within an hour, the drive is put back in DMA mode.  I don't
> know exactly what causes this but suspect that the device is polled for
> autotuning after rmmod unloads the cdrom driver and subsequently resets
> the device for DMA.
>
> I know I could pass the kernel parameter "ide1=nodma" at boot time but
> the IDE channel is shared with a hard disk that I would like to keep in
> DMA mode if I could.

I think you need to add '-k 1' to that command-line to keep settings across
bus scans.  Try 'hdparm -d0 -k1 /dev/hdd' and see if that does it.