port-arm32: DIMM Modules! bus_dma functions on arm32?

Subject: DIMM Modules! bus_dma functions on arm32?
To: 'port-arm32@netbsd.org' <port-arm32@netbsd.org>
From: Bruce Martin <BruceM@cat.co.za>
List: port-arm32
Date: 09/13/1999 22:18:16
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Hi all,

After extensive bug searching into the problem of DMA accesses being
unsuccessful on the arm32 (the EBSA285 in particular), it was discovered
that the problem was only an incorrect DIMM module! The EBSA board
specifies that only 2- or 4-array DIMMs may be used, while we had an
8-array part in. Putting a 4-array DIMM in seemed to solve the problem.
Please keep that in mind if you are every having memory transfer related
problems on the EBSA285.

Now, upon getting DMA to work, we have noticed some rather long delays
on the PCI bus, which are not present on the i386. We have veen looking
through the arm code, to check the settings of the various 21285 DMA
Control and DMA Configuration registers, but after extensive searching,
have found that no access is made to any of these registers anywhere
under NetBSD. However, it seems that DMA is working in some way. Please
could anybody familiar with DMA on the arm32 (and EBSA285) tell us how
it has been implemented without accessing any of the 21285 DMA
registers?

Thanks in advance.

Bruce Martin

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<P><FONT SIZE=3D2>Hi all,</FONT>
</P>

<P><FONT SIZE=3D2>After extensive bug searching into the problem of DMA =
accesses being unsuccessful on the arm32 (the EBSA285 in particular), =
it was discovered that the problem was only an incorrect DIMM module! =
The EBSA board specifies that only 2- or 4-array DIMMs may be used, =
while we had an 8-array part in. Putting a 4-array DIMM in seemed to =
solve the problem. Please keep that in mind if you are every having =
memory transfer related problems on the EBSA285.</FONT></P>

<P><FONT SIZE=3D2>Now, upon getting DMA to work, we have noticed some =
rather long delays on the PCI bus, which are not present on the i386. =
We have veen looking through the arm code, to check the settings of the =
various 21285 DMA Control and DMA Configuration registers, but after =
extensive searching, have found that no access is made to any of these =
registers anywhere under NetBSD. However, it seems that DMA is working =
in some way. Please could anybody familiar with DMA on the arm32 (and =
EBSA285) tell us how it has been implemented without accessing any of =
the 21285 DMA registers?</FONT></P>

<P><FONT SIZE=3D2>Thanks in advance.</FONT>
</P>

<P><FONT SIZE=3D2>Bruce Martin</FONT>
</P>

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