hdparm confusion

From: Sybren Stuvel (sybrenUSE_at_YOURthirdtower.com.imagination)
Date: 07/03/05 

Date: Sun, 3 Jul 2005 13:11:21 +0200

Hi folks!

I'm confused. At this moment, I'm ripping a DVD. My computer slows
down, even my mouse cursor is laggy. Even worse: vim is slow! The
first thing that comes to my mind is that my DVD drive doesn't use
DMA. Of course, I wanted to check, so I did "hdparm -i /dev/dvd":

/dev/dvd:

 Model=PHILIPS DVDR824DP, FwRev=P3.0, SerialNo=
 Config={ Fixed Removeable DTR<=5Mbs DTR>10Mbs nonMagnetic }
 RawCHS=0/0/0, TrkSize=0, SectSize=0, ECCbytes=0
 BuffType=unknown, BuffSize=0kB, MaxMultSect=0
 (maybe): CurCHS=0/0/0, CurSects=0, LBA=yes, LBAsects=0
 IORDY=yes, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes: pio0 pio1 pio2 pio3 pio4
 DMA modes: mdma0 mdma1 mdma2
 UDMA modes: udma0 udma1 *udma2
 AdvancedPM=no
 Drive conforms to: device does not report version:

 * signifies the current active mode

As you can see, it appears to be using DMA. Now see the output of
"hdparm /dev/dvd":

/dev/dvd:
 IO_support = 0 (default 16-bit)
 unmaskirq = 1 (on)
 using_dma = 0 (off)
 keepsettings = 0 (off)
 readonly = 0 (off)
 readahead = 256 (on)
 HDIO_GETGEO failed: Invalid argument

Which confirms my suspicion that DMA isn't used. I'm confused. How can
one part of hdparm tell me DMA is on, while another part tells me DMA
is off?

I'm using Linux 2.6.10-5-386 on Ubuntu Linux.

Oh, if I try turning DMA on, I get:

# hdparm -d 1 /dev/dvd

/dev/dvd:
 setting using_dma to 1 (on)
  HDIO_SET_DMA failed: Operation not permitted
   using_dma = 0 (off)

The DVD drive and my motherboard (ASUS A7V8X, via82cxxx module loaded)
do support DMA. It all used to work properly when I had Gentoo.

Sybren 

-- 
The problem with the world is stupidity. Not saying there should be a
capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself? 
                                             Frank Zappa

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