How to turn on/off DMA

[Doncho N. Gunchev]

On Wednesday 2007-05-02 00:16:37 dragoran dragoran wrote:
> On 5/1/07, Doncho N. Gunchev <gunchev at gmail.com> wrote:
> > On Tuesday 2007-05-01 23:21:53 dragoran dragoran wrote:
> > > On 5/1/07, Doncho N. Gunchev <gunchev at gmail.com> wrote:
> > > > On Tuesday 2007-05-01 21:52:04 you wrote:
> > > > >   I installed F7t4 from the KDE live CD, my hardware profile is:
> > > > > ebf36068-3809-426c-ade0-d0c531b5b402. Here are the results:
...
> > > > OT: Now, when hdparm -d 0/1 does nothing, how can I switch DMA on/off
> >
> > for
> >
> > > > my
> > > > DVD-Writer and hard disk?
> > >
> > > there is no reason to turn it off the new driver should select and set
> >
> > the
> >
> > > best dma mode that your drive/chipset supports; if not its a bug.
> >
> > I know it should (remember when these settings got removed from
> > /etc/sysconfig/*?), that's why I asked 'how?'. My DVD-Writer seems
> > to not use any DMA at all (~1MB/sec vs >4MB/sec in FC6). How do
> > I know if it uses "the best mode", if I can't try any other?
>
> its simple a higher dma mode means higher speed.
> what does hdparm -i /dev/yourdevice show?
> (both fc6 and f7 output) ?
>

What was not clear in my question, I asked how do I do turn DMA on/off with 
the new kernels, not why I should not do this? Is there a reason to keep this 
secret?

Here's the info for my DVD-Writer, it has DMA off in FC6 and I'm turning it on 
in rc.local to get it working faster. I also have to 'killall 
hald-addon-storage' (or more specificly, the one that monitors my DVD) or the 
machine (laptop) will die in a few hours (does not matter if I have DMA on, 
off or if I try to play with /usr/share/hal/fdi/policy/10osvendor/*.fdi. 
Haven't seen it locking for this reason with F7t4 yet.
--- Fedora Core 6 ---
# hdparm -i /dev/hdb

/dev/hdb:

 Model=TSSTcorpCD/DVDW TS-L632D, FwRev=AC01, 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=on/off, tPIO={min:227,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

 * signifies the current active mode

# hdparm /dev/hdb

/dev/hdb:
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  0 (off)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 HDIO_GETGEO failed: Inappropriate ioctl for device

*** There is a difference when hdparm /dev/hdb shows DMA on - when I watch DVD 
movie it works (and the time taken by the kernel while reading the DVD drops 
down), when off - it skips frames and looses a/v sync.
--- Fedora 7 test 4 ---
# ll /dev/dvdrw
lrwxrwxrwx 1 root root 4  2 май  0,56 /dev/dvdrw -> scd0
# hdparm -i /dev/scd0

/dev/scd0:

 Model=TSSTcorpCD/DVDW TS-L632D                , FwRev=AC01    , 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=on/off, tPIO={min:227,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

 * signifies the current active mode

# hdparm /dev/scd0

/dev/scd0:
 IO_support   =  0 (default 16-bit)
 readonly     =  0 (off)
 readahead    = 256 (on)
 HDIO_GETGEO failed: Inappropriate ioctl for device

-- 
Regards,
  Doncho