Re: [PATCH] ide: motherboard-info based blacklist for ide-dma

From: Sergei Shtylyov
Date: Fri Jan 16 2009 - 07:36:06 EST


Dmitry Gryazin wrote:

True. However it should be possible to handle it correctly by adding
DMA quirk to the respective host drivers (seems to be via82cxxx.c in
case of
Yeah, this seems a viable approach...
Kirill, could you please look into adding such quirk to via82cxxx

[ It seems the best place to add it would be via_init_one() as we
could just
No, not really -- the issue is not at all as simple as this patch
tried to present it. Looking at its "Quick Startup Reference"
(, the EPIC
board has *two* normal IDE connectors in addition to the CF slot
(connected to the secondary port -- and it seems possible that a hard
drive can be connected to the same port as CF), so the right place
seems to rather be in [mu]dma_filter() methods -- and the decision
should be strictly based on the drive type indicating CF, i.e. by
calling ata_id_is_cfa().

As you suggest, we could use the following criterions:

Board vendor="FIC" &&
Board name="PT-2200" &&
VIA-family IDE controller &&
drive type=CF

Yes, but in almost exactly opposite order (well one check shoud be added)

VT82C686 (or whatever) and
secondary channel and
CFA device and
DMI ID is FIC PT2200

It should work good enough.

To test it I also tried to install external IDE CF adaptor to the secondary IDE controller (both master and slave).

You mean that this adaptor is directly connected to IDE slot with the cable... hm, haven't seen those.

And it's also identified as CF drive type. And we turn off DMA for it. But since external CF adaptor could be wired right, turning DMA off would be incorrect in some cases.

Yes, _that_ particular external IDE/CF adaptor that we bought, has the same problem, so turning DMA off on it should be correct. We even decided to verify ourselves that wrong soldering is the cause of problems, and wired manually necessary pins, and, voila, DMA works. So the question is:

Is it right to implement the above-mentioned criterion, which would work correctly in 99 cases of 100, but will pessimistically turn DMA off in
rare cases (e.g. rightly wired external IDE/CF adaptor attached to
PCISA/C3), or is the whole problem unsolvable?

Good question. However, with the on-board CF adapter already present on the seconary channel it seems improbable that the user will need to connect another (external) CF adapter. Even if he'd need it, he'd still be able to use the primary port.

We could not come up with the right criterion which selects exactly on-board CF slot, so if there is no satisfactory 100% reliable solution maybe it doesn't make sense to continue...

I think it still does make sense.

MBR, Sergei

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