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Date: Sat, 17 Aug 2002 11:30:33 -0700 (PDT)
From: Andre Hedrick <andre@linux-ide.org>
To: Anton Altaparmakov <aia21@cantab.net>
cc: Jan-Benedict Glaw <jbglaw@lug-owl.de>, linux-kernel@vger.kernel.org
Subject: Re: IDE?
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Anton,

They will become PIO over DMA, and it will become interesting.
But you are correct, we are stuck wit PIO regardless.

Andre Hedrick
LAD Storage Consulting Group

On Sat, 17 Aug 2002, Anton Altaparmakov wrote:

> At 19:16 17/08/02, Jan-Benedict Glaw wrote:
> >On Fri, 2002-08-16 18:35:29 -0700, Linus Torvalds <torvalds@transmeta.com>
> >wrote in message <Pine.LNX.4.44.0208161822130.1674-100000@home.transmeta.com>:
> > > On Fri, 16 Aug 2002, Alexander Viro wrote:
> >
> > >     - in particular, it would only bother with PCI (or better)
> > >       controllers, and with UDMA-only setups.
> >[...]
> > > And then in five years, in Linux-3.2, we might finally just drop support
> > > for the old IDE code with PIO etc. Inevitably some people will still use
> >
> >That's bad. Then, you're nailed to use old kernels without having
> >possibilities of recent kernels only because you're working with eg. old
> >Alphas, PCMCIA-IDE things or so? Bad, bad, badhorribly bad. Even it's
> >sloooow, there'll always some need for PIO-only controller support...
> 
> I don't think it is possible to have DMA only drivers. On DMA 
> failure/timeouts/whatever, the current DMA drivers always fall back to PIO 
> mode and this is a good thing. Otherwise many transfers would simply fail. 
> Dropping PIO mode fallback would mean a lot of IO errors. Any system put 
> under stress will at some point fall back to PIO mode (at least judgjing 
> from the limited number of systems I have) because it doesn't manage to do 
> the DMA transfers in time. That was very visible during the period when 
> Andre's new IDE core went into 2.5.something_early and it turned out that 
> PIO was broken at that point. For example my VIA box was running just fine 
> then in DMA mode but as soon as I put it under stress it blew up due to it 
> falling out of DMA and the then broken PIO mode... And VIA686b is 
> mainstream hardware...
> 
> Best regards,
> 
>          Anton
> 
> 
> -- 
>    "I've not lost my mind. It's backed up on tape somewhere." - Unknown
> -- 
> Anton Altaparmakov <aia21 at cantab.net> (replace at with @)
> Linux NTFS Maintainer / IRC: #ntfs on irc.openprojects.net
> WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/
> 
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