IDE (hpt370) and DMA mode switching (again)...

[newsgate@impure.org.uk (Rob Andrews)]

Hello,

I wrote about a week or so ago about switching DMA modes on the HPT370
controller.

I've been fiddling and have found something odd.

If I compile a kernel without the 'HPT370' option in the IDE/ATA config,
the machine starts okay, and after turning DMA on, the drive fetches about
21.5MB/s. hdparm tells me the drive/chipset is in udma4. I can change the
DMA mode without crashing, although if I change out of udma4, I can't set
it back to udma3/udma4 (states that the mode is not functional).

If I compile a kernel /with/ the 'HPT370' option in the IDE/ATA config, the
machine starts okay, turns DMA mode on itself, and puts the drive into
udma2. The drive fetches 17.4MB/s. If I change DMA mode, the machine crashes.
No kernel panic, nothing - just completely dead.

Any ideas?

-- 
Rob                                 off list/ng replies: rob@impure.org.uk
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