From: mru@kth.se (Måns Rullgård)
To: linux-kernel@vger.kernel.org
Subject: Re: HPT372 DMA corruption
Date: Wed, 14 Jan 2004 01:05:17 +0100 [thread overview]
Message-ID: <yw1xu12z9yyq.fsf@kth.se> (raw)
In-Reply-To: <20040113183029.A16406@timetrax.localdomain>
Chuck Berg <chuck@encinc.com> writes:
> 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.
Well, VIA never did have a good reputation.
> 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.
Is it always a multiple of 4 bytes? Is there any pattern in the
position of the corruption, such as always aligned to some value?
> 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.
Could something be cutting off the DMA transfer too early?
--
Måns Rullgård
mru@kth.se
next prev parent reply other threads:[~2004-01-14 0:08 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
2004-01-14 0:05 ` Måns Rullgård [this message]
2004-01-23 2:27 ` Andre Hedrick
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