Disable DMA.

[Ian Lepore]

On Sun, 2012-02-12 at 10:29 +0100, Peter Ankerstål wrote:
> On Feb 11, 2012, at 9:34 PM, Alexander Motin wrote:
> 
> > On 02/11/12 20:15, Peter Ankerstål wrote:
> >> In FreeBSD 8 i used the loader-variable hw.ata.ata_dma=0 to get my computer boot on a CF card. But
> >> in FreeBSD 9.0 it doesn't seem to work. Could it be another variable or is it something else that doesn't work
> >> in 9? The machine boots up the installer when the CF-card is not present but when it is present it stops right
> >> after the "Timecounter" stuff.
> > 
> > On 9.0 you can to it with
> > hint.ata.X.mode=PIO4
> > , where X is a bus number.
> > 
> > In recent 8/9-STABLE I've also resurrected hw.ata.ata_dma=0.
> > 
> That works, thanks!

It's also useful to try modes other than PIO4 when using the
finer-grained mode= control.  We've been disabling dma completely on
SBCs with CF sockets for years due to the kind of lockup you mention,
but I recently discovered that some units run just fine with mode=WDMA2
(but not any dma modes faster than that).

-- Ian