From: Chuck Berg <chuck@encinc.com>
To: Linux kernel <linux-kernel@vger.kernel.org>
Cc: "Richard B. Johnson" <root@chaos.analogic.com>
Subject: Re: HPT372 DMA corruption
Date: Tue, 13 Jan 2004 18:30:29 -0500 [thread overview]
Message-ID: <20040113183029.A16406@timetrax.localdomain> (raw)
In-Reply-To: <Pine.LNX.4.53.0401091517390.1022@chaos>; from root@chaos.analogic.com on Fri, Jan 09, 2004 at 03:24:28PM -0500
On Fri, Jan 09, 2004 at 03:24:28PM -0500, Richard B. Johnson wrote:
[cmp -l bad good]
> > 89260029 0 31
> > 89260030 0 327
> > 89260031 0 200
> > 89260032 0 13
>
> Since whole bytes are not written, this looks strangely like
> an attempt to DMA to cached RAM! Since the CPU didn't write
I tested this by reading with O_DIRECT, and immediately after each read(),
read all of a 1MB array (my cache is only 256kB), and then checking the
data. The same corruption occurs.
Via had a DMA corruption bug a couple years ago with similar symptoms,
apparently with the VT82C686B southbridge. Mine is a VT82C586B (which some
people also reported problems with). My board dates long after these
problems were discovered, so I sure hope it's not the same bug. I'll try
upgrading my BIOS to the latest version in case Soyo's changelog is not
entirely honest.
I did learn some more about the pattern of corruption. The data is not
being written to memory - the "bad" data is whatever happened to be there
before. It usually happens in 4, but sometimes 64 or 32 byte chunks.
When I read from the device with O_DIRECT, the corruption only appears at the
very end of the read. I've confirmed this for reads of 512 bytes through 256k
at multiples of 512 bytes.
next prev parent reply other threads:[~2004-01-13 23:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-01-09 20:05 Chuck Berg
2004-01-09 20:24 ` Richard B. Johnson
2004-01-13 23:30 ` Chuck Berg [this message]
2004-01-14 0:05 ` Måns Rullgård
2004-01-23 2:27 ` Andre Hedrick
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