WDC drive with ultra-DMA support?

stople · 06-09-2008, 03:28 PM

I cannot enable DMA on my Western Digital Caviar GP 1TB. When I try to hdparm -d1 /dev/hda it responds "HDIO_SET_DMA failed: Operation not permitted". I found an kernel configuration option, ALI M15x3 WDC support (DANGEROUS), which appears that I am a fool if I enable. I also found that the only blacklisted hard drives in ultra-DMA is WDC drives (dunno if this includes my disc). Can anyone explain why it is blacklisted (except that it "may cause corruption of data")? Is there any work in progress with this issue, where I maybe can contribute? In short: is there any hope for me to enable DMA on my hard drive?

stefan_nicolau · 06-13-2008, 10:07 AM

DMA is enabled by default and cannot be controlled on sata drives.

stople · 06-24-2008, 03:38 PM

Note: This probably only regards Slackware 12.1 users.

I found the article I was looking for (Slackware 12.1 & DMA). I forgot to mention that my hard drive was SATA, and that it was named /dev/hda. I think this problem is regarding Slackware 12.1. According to what I found, "it seems that the generic-smp kernel that ships with Slackware Linux 12.1 is build to first probe for ide before loading libata". The solution was to append hda=noprobe in lilo.conf. I have found this solution before and tried it, but then it resulted in a kernel panic during boot. But the article I found wrote something about an init ram disk (initrd), and by using it I made it work.

I did it the following way:
Make the initrd disk by using mkinitrd, and mount root to /dev/sda5 (my root file system was /dev/hda5), mkinitrd -c -k 2.6.25.6-smp -m reiserfs -r /dev/sda5
Modify /etc/fstab; change all /dev/hda* to /dev/sda*
Modify /etc/lilo.conf; add the following: append = " hda=noprobe"
Applying lilo.conf by running "lilo" from shell
Reboot
After rebooting I checked in my /dev folder, and I found that all the hda* devices that was the partitions on my hard drive was now sda*
Then I modified lilo.conf again; I changed boot from /dev/hda to /dev/sda, and root from /dev/hda5 to /dev/sda5. Don't change append hda=noprobe to sda=noprobe! I did it, with bad results....
Apply lilo.conf
Reboot