Re: [PATCH 1/1] ide: Allow disabling of UDMA for Compact Flash devices

[Robert Hancock <hancockr@shaw.ca>]

James Ausmus wrote:
> This is exactly the situation that I have with 2 separate "dumb" (just
> physical interfaces, essentially - not at all detectable) IDE->CF
> adapters - both the IDE controller and the CF media support several
> UDMA modes, so the IDE driver throws the CF device into UDMA mode on
> bootup. However, as the physical interface between the IDE cable and
> the CF socket is poorly engineered, it cannot handle the higher
> speeds, causing the timeout errors. For some people, this can just be
> fixed with an ide=nodma boot option, but as I also have a (quite
> large) rotating media device on the controller, this is not an option,
> as, if a fsck is performed on a boot, the boot-up time is upwards of
> 30 minutes.

If it's like some of the CF-IDE adapters I've seen, the DMA request/ack 
lines likely aren't even wired up between the card and the cable. 
There's no way the kernel can detect that DMA is not actually possible 
on such a card without trying and waiting for it to timeout. (I've seen 
a few which have jumpers which select whether to connect these or not - 
haven't a clue why you wouldn't want to hook those up unconditionally..)

Isn't there an option to disable DMA for a specific IDE channel 
(ide2=nodma or something like that)?

-- 
Robert Hancock      Saskatoon, SK, Canada
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