Messages in this thread | | | Subject | Re: [PATCH] PnP Fixes for 2.6.0-test5 | From | Alan Cox <> | Date | Mon, 22 Sep 2003 12:32:15 +0100 |
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On Sul, 2003-09-21 at 21:11, Adam Belay wrote: > # -------------------------------------------- > # 03/09/21 ambx1@neo.rr.com 1.1357 > # [PNP] remove DMA 0 restrictions > # > # The original argument for blocking DMA 0 was to avoid conflicts with > # "memory refresh" but such configurations are only found on very old > # 8-bit systems that are likely not supported by the linux kernel.
DMA0 is used by lots of 386/486 era systems for memory refresh. It is also "borrowed" by some other systems that know it isnt available to the OS. There are a couple of heuristics I've seen suggested by vendors of things like sound cards
1. Check the PnPBIOS information (never looked into this myself) 2. Assume DMA 0 is free if the machine has a PCI bus detected 3. Read the DMA 0 counter a few times. If it is continually changing don't use DMA 0
#2 is certainly a good idea IMHO, I don't know how well the others work. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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