CDROM/DVDROM drives on SATA IDE = no DMA

[wwp]

Hello,


On Thu, 25 May 2006 09:43:39 -0500 Brian Millett <bmillett at gmail.com> wrote:

> On Thu, 2006-05-25 at 09:14 -0300, Marcelo Magno T. Sales wrote:
> > Hi,
> > 
> > I have several desktop machines and notebooks which have CDROM / DVDROM 
> > connected to IDE SATA interfaces and they all have DMA disabled. Every
> > time the CDROM/DVDROM drives are accessed, the computers slow down a lot
> > and become almost unusable till it's finished. hdparm shows:
> > [marcelo.sales at sf002698 ~]$ /sbin/hdparm /dev/dvd
> > 
> > /dev/dvd:
> >  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
> > 
> > 
> > When I try to enable DMA using hdparm, I get:
> > [root at sf002698 ~]# hdparm -d1 /dev/dvd
> > 
> > /dev/dvd:
> >  setting using_dma to 1 (on)
> >  HDIO_SET_DMA failed: Operation not permitted
> >  using_dma    =  0 (off)
> > 
> > 
> > Checking the config file for the stock kernel installed in these
> > machines, I see:
> > [marcelo.sales at sf002698 ~]$ grep _BLK_ /boot/config-$(uname -r) | grep
> > SATA # CONFIG_BLK_DEV_IDE_SATA is not set
> > 
> > I assume this is the reason why I can't turn on DMA, am I right? I
> > believe many, many people shall suffer from this problem too. Should I
> > open an RFE asking to enable this in the next kernel or is there a
> > specific reason for not enabling this in the stock kernels? I hope I'll
> > not need to recompile the kernel and install it in all these machines
> > just because of this :)
> 
> 
> Please do.
> 
> To get good performance I have to add the following to the boot kernel
> parameters:
> 
>  combined_mode=libata atapi_enabled=1
> 
> But the DMA is still not activated, however I can watch DVDs & burn
> cd/dvds ok.

Here I added hdc=noprobe to the kernel boot options (grub).


Regards,

-- 
wwp
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