On Sat, Dec 18, 1999 at 11:20:51PM +0100, Martin Blapp wrote:
>
> Sorry,
>
> I found a rather easy workaround. Disable DMA for
> the disks in the BIOS ... But I still wonder why
> enable/disable ATA DMA in kernel has no effect for
> this crash. Why does only the BIOS disable help ?
Purely a wild guess on my part:
If the BIOS is set to enable UDMA, then the bios sets both
the controller and the disk for UDMA. But, the ata driver
tries to set the disk to WDMA2 mode for "generic drivers".
If the controller is set for UDMA and the disk for WDMA2, they
might have problems communicating (the "generic driver" doesn't
try to mess with the controller settings, I don't think).
However, if the BIOS sets the disk and the controller to
PIO, then when the ata drivers uses the "generic" treatment
to set the disk to WDMA2, this works since PIO and WDMA2
have similar timings.
As I said, this is purely a wild guess from someone who
understands all this poorly.
--
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