From: Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>
To: Chris Cheney <ccheney@cheney.cx>
Subject: Re: bugme #1217: "Use PCI DMA by default when available" does not work
Date: Sat, 22 Nov 2003 23:20:18 +0100
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Chris, please post output of 'lspci -vvv -xxx' - it will be very useful.
We can see what registers are programmed differently when autodma is off.

--bart

On Saturday 22 of November 2003 21:48, Chris Cheney wrote:
> I sent the following followup report to the bug I filed at
> bugme.osdl.org several months ago about my hpt372 ide controller being
> slow.
>
> I have determined what causes the dramatic slowdown problem. It is not
> drive specific but it may be specific to the hpt controllers. The
> problem is due to using automatic dma. If I don't have the following
> two options set in my kernel then it runs at full speed when I turn on
> dma with hdparm. Otherwise using automatic dma I get somewhere between
> a 50% - 700% slowdown on writes, reads seem to not be as badly affected.
> This is reproducible on both 2.4.23-rc1-xfs and 2.6.0-test9-bk24 (the
> two I tested on).
>
> CONFIG_IDEDMA_PCI_AUTO=3Dy=20
> CONFIG_IDEDMA_AUTO=3Dy=20

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