Re: DMA not working

[Florian Kulzer <florian@molphys.leidenuniv.nl>]

Hi Lorenzo,

> I'm using kernel 2.6.12.4 (vanilla), recompiled, on a Kubuntu, and when 
> I try to enable DMA, I get this error:

>  HDIO_SET_DMA failed: Operation not permitted
>  using_dma    =  0 (off)

> lspci | grep IDE
> 0000:00:1f.1 IDE interface: Intel Corp. 82801DBM (ICH4) Ultra ATA 
> Storage Controller (rev 01)

I have the same controller (rev 03, however) and I never got DMA to work 
when PIIX was loaded as a module. Once I compiled it statically into my 
kernel (currently a custom 2.6.12 on a Debian Sid system) the problem 
vanished without further work and DMA was activated automatically when I 
booted into the new kernel.

I then tweaked my /etc/hdparm.conf a bit more (hdc is a dvd/cdrom):

/dev/hda {
        mult_sect_io = 16
        dma = on
        io32_support = 1
        interrupt_unmask = on
}

/dev/hdc {
        dma = on
        io32_support = 1
        interrupt_unmask = on
}

The main increase in speed, however, came from just turning on DMA. (3-4 
times faster for 'hdparm -t /dev/hda')

I hope this helps.

Regards,
         Florian