DVD-Rom: DMA is disabled

R.M.Albrecht romal at gmx.de
Fri Aug 25 14:39:28 UTC 2006


Hi,

while testing a dvd with mplayer, I noticed, that mplayer is dropping
frames and the cpu-scaling is glued to the maximum of 1.73GHz.

I think the problem is the disabled dma for the dvd-drive:

[root at helios ~]# hdparm -d /dev/hdc
/dev/hdc:
 using_dma    =  0 (off)

But I can't enable it:

[root at helios ~]# hdparm -d 1 /dev/hdc
/dev/hdc:
 setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Operation not permitted
 using_dma    =  0 (off)

After some playing with hdparm

hdparm -c3 -u1 -a64 -k1 /dev/hdc

seems to improve the situation a lot. The cpu comes down to 800 Mhz and
no frame are dropped.

But the canoncial solution would be to enable DMA ? Has anyone an idea
where the problem lies ?

The hardware:

[root at helios etc]# dmesg | grep hd
hdc: UJDA750 DVD/CDRW, ATAPI CD/DVD-ROM drive
hdc: ATAPI 24X DVD-ROM CD-R/RW drive, 2048kB Cache
hdc: CHECK for good STATUS
hdc: CHECK for good STATUS

[root at helios etc]# lspci | grep Intel
00:1f.2 IDE interface: Intel Corporation 82801FBM (ICH6M) SATA
Controller (rev 03)

cu romal





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