CDROM/DVD DMA

[scullyt]

Can anyone give me some clues as to how to enable DMA support on my DVD drive? I have had problems with choppy DVD playback on MPlayer and have been informed that this is the answer to my problem. I am using kernel-2.6.6-rc1.

[Sipi]

First, emerge hdparm. Than edit /etc/conf.d/hdparm. Here you have two choices: add harddrive-tuning values separately (for each drive) or for once, for eac drive.

I recommend the first. So, you need to define cdrom0_args or cdrom1_args, depending on your DVD drive. (If this is the first DVD/CDROM device, cdrom0, etc.)

You need to add:

cdrom0_args="-d1" to enable DMA access. Furthermore, you should add "-X..", which enables UDMA modes. You need to run "hdparm -i /dev/hxy" to see which modes your DVD drive knows, where xy is the number of DVD drive (computed by your primary/secondary IDE channel and master/slave settings).

For example, if it says it knows MDMA2, you should set "-X32" for multimode DMA mode 2. "-X18" sets singleword DMA mode 2, and "-X66" sets Ultra DMA mode 2.

Beware, these -X settings can cause massive freezes if your controller/device has problems or does not know the desired transfer.

Regards,
Sipi