From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20030225 Description of problem: With redhat9, the "modprobe ide-cd dma=1" function no longer works, returning "Warning: ignoring dma=1, no such parameter in this module". Searching google, I found that the DMA should be set using "hdparm -d 1 /dev/cdrom", which returns "/dev/cdrom:\n using_dma = 1 (on)" (/dev/cdrom is a symlink to /dev/hdd, the DVD drive). However, the choppiness and skipped frames continue. The hdparm does not seem to actually enable DMA on the DVD-ROM. Please reference this lkml thread: http://www.ussg.iu.edu/hypermail/linux/kernel/0303.0/0006.html Version-Release number of selected component (if applicable): kernel-2.4.20-8 How reproducible: Always Steps to Reproduce: 1. Install Redhat 9 on i386 platform 2. Type "hdparm -d 1 /dev/<dvddevice>" at a root prompt 3. Play any DVD Actual Results: The DVD played with many dropped frames (on an athlon 1.4ghz with 512mb ram) Expected Results: The DVD should have played smoothly just as it did before installing redhat9 (from redhat8). Additional info: This bug is reproducible with both xine and ogle, and it was not appareant in the previous release of redhat (8) (after you put "options ide-cd dma=1" in /etc/modules.conf).
I was under the impression that Red Hat Linux 8.0's kernels had turned DMA off on CD-*s and DVD-*s as a safety precaution that could be overridden by the aforementioned parameter that you specified. I would think that this would have probably been corrected (or worked around) in Red Hat Linux 9's kernel (no mention of that DMA is disabled by default in the release notes). I am not seeing any such problems on my i440BX/Toshiba DVD-ROM setup. If you do a plain dump of the hdparm on /dev/hdd what does it show? What kind of chipset are you using?
The IDE Controller is on my Abit KT7-RAID motherboard (not using the RAID controller) which uses the via kt133 chipset. The output of hdparm /dev/hdd is: hdparm /dev/hdd /dev/hdd: HDIO_GET_MULTCOUNT failed: Invalid argument IO_support = 1 (32-bit) unmaskirq = 1 (on) using_dma = 1 (on) keepsettings = 0 (off) readonly = 1 (on) readahead = 8 (on) HDIO_GETGEO failed: Invalid argument From the aforementioned linux kernel mailing list i assumed this issue has been noticed before.
Solution/Workaround found: Appareantly something is either fishy with my DVD drive or IDE controller... or they just don't like each other. Anyway, i used hdparm -i /dev/hdd and found out that the dma was set to udma2. I thought possibly that was the problem so i used hdparm -d 1 -X mdma2 and now all runs smoothly. Either 2.4.18 wasn't trying udma or some combination of my IDE controller, dvd drive, udma, and 2.4.20 is causing things to fail. Thank you.