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From: <benh@kernel.crashing.org>
To: Andrew Morton <akpm@zip.com.au>
Cc: Ed Sweetman <ed.sweetman@wmich.edu>,
        Kristian <kristian.peters@korseby.net>, <linux-kernel@vger.kernel.org>
Subject: Re: [CFT] Bus mastering support for IDE CDROM audio
Date: Mon, 28 Jan 2002 10:51:36 +0100
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>At no stage does a packet-mode DMA error turn off drive-level
>DMA.  This is because some devices seem to perform ordinary
>ATA DMA OK, but screw up packet DMA.
>
>The kernel internally retries the requests when it performs fallback,
>so userspace shouldn't see any disruption as the kernel works
>out what to do.
>
>Once the drive has fallen back to single-frame (or PIO mode) for
>packet reads, the only way to get it back to a higher level is
>a reboot.

Doesn that mean that a bad media (typically a scratched CDROM) will
cause the drive to revert to PIO until next reboot ?

Ben.


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