Re: simplex IDE

mlord (mlord@pobox.com)
Tue, 07 Apr 1998 21:38:45 -0400


Albert D. Cahalan wrote:
>
> >> PCI_IDE: simplex device: DMA disabled
> >> ide1: PCI_IDE Bus-Master DMA disabled (BIOS), pcicmd=0x0005,
> >> ccode=0x101ea0a, dma_base=0x000

> > Your chipset reports that it is semi-broken,
> > in that it cannot perform DMA transfers on
> > both IDE ports simultaneously.
> >
> > That is just too weird for the current IDE driver,
> > so we just plain don't do DMA on such chipsets.
> > Most PCI chipsets do NOT have this problem.
...
> Pick the port most likely to _need_ the DMA and just assign
> the DMA support to the one port. Never mind sharing DMA.

The code does use DMA for one of the ports already:
always choosing the primary port. We cannot easily
guess which devices will see more use, and this is
a rare situation anyway. So, the driver just picks
the primary port for DMA, does PIO on the second port,
and the user could re-cable if that isn't ideal..

Cheers!

-- 
mlord@pobox.com
The Linux IDE guy

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