Messages in this thread | | | From | (Måns Rullgård) | Subject | Re: HPT372 DMA corruption | Date | Wed, 14 Jan 2004 01:05:17 +0100 |
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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
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