On Tue, May 25, 1999 at 02:07:41PM +1000, Chris Baird wrote:
> I've upgraded to a K6-2/300 with an "A plus" VT82C586/MVP3-based
> motherboard (order of magnitude upgrade!), but there's several
> problems with the kernel and device recognition. (Possibly BIOS PnP
> configuration pilot errors, that frustratingly haven't been solved
> yet..)
> 
> > Problem #1
> 
> wd0 claims to support PIO mode 3 with DMA mode 1, but after pciide0
> loses an interrupt it needs to drop DMA for it to work.  The relevant
> kernel messages:
> 
>         wd0 at pciide0 channel 0 drive 0: <QUANTUM MAVERICK 540A>
>         wd0: drive supports 8-sector pio transfers, lba addressing
>         wd0: 32-bits data port
>         wd0: drive supports PIO mode 3, DMA mode 1
>         wd0(pciide0:0:0): using PIO mode 3, DMA mode 1 (using DMA data transfers)
> 
> [later, when trying to use wd0 for the first time]
> 
>         pciide0:0:0: lost interrupt
>                 type: ata
>                 c_bcount: 512
>                 c_skip: 0
>         pciide0:0:0: Bus-Master DMA error: missing interrupt, status=0x20
>         wd0d: DMA error reading fsbn 0 (wd0 bn 0; cn 0 tn 0 sn 0), retrying
> [repeated]
>         wd0: transfer error, downgrading to PIO mode 3
>         wd0(pciide0:0:0): using PIO mode 3
>         wd0d: DMA error reading fsbn 0 (wd0 bn 0; cn 0 tn 0 sn 0), retrying
>         wd0: soft error (corrected)
> 
> Is there a way to disable DMA [from the kernel config]? (I've noticed
> flags can enable DMA...)

Yes, you need to put the flag on the 'wd*' declaration. Something like:
wd*     at pciide? channel ? drive ? flags 0x0ff0

see wd(4) for details, or the i386 GENERIC kernel config file.

--
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
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