Enabling DMA.

[Alex Goddard]

Installation and everything has been painless, everything more or less 
worked out of the box.  However, there's one last rough edge I need to 
sort out: DMA on my IDE devices.  I have two SATA drives and two plain old 
IDE devices (a hard disk and a DVD burner).  The SATA drives work 
perfectly, however I cannot get DMA to turn on for either the DVD burner 
or that hard disk.

The kernel is the Ubuntu-provided 2.6.8.1-3-amd64-generic, the motherboard 
is an Asus A8V.  DMA just worked under my previous distro, so I'm pretty 
certain it's not a hardware issue.pretty certain it's not a hardware 
issue.  I haven't touched the BIOS since well before installing Ubuntu, 
and DMA worked under my previous distro (Gentoo).  So for the moment I'm 
pinning the blame on Ubuntu.

sudo hdparm -d1 /dev/hdX gives me HDIO_SET_DMA failed: Operation not 
permitted.

The weird part is this: The right IDE module for my hardware is loaded (in 
this case via82cxxx).  There is nothing suspicious in lspci (it sees and 
correctly identifies the IDE controller).  The only notable bit of dmesg's 
output is this:

Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx

Any ideas what to do about this?  It seems like the via82cxxx module isn't 
loaded when the kernel initially encounters the IDE devices, so they use 
some default driver that won't allow me to enable DMA, but I have no idea 
what to do about it except perhaps recompiling my kernel myself with the 
proper bits compiled in instead of as modules.

-- 
Alex Goddard
agoddard at purdue dot edu