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    SubjectRe: SATA exceptions with 2.6.20-rc5
    On 2007.01.15 18:34:43 -0600, Robert Hancock wrote:
    > Björn Steinbrink wrote:
    > >>My latest bisection attempt actually led to your sata_nv ADMA commit. [1]
    > >>I've now backed out that patch from 2.6.20-rc5 and have my stress test
    > >>running for 20 minutes now ("record" for a bad kernel surviving that
    > >>test is about 40 minutes IIRC). I'll keep it running for at least 2 more
    > >>hours.
    > >
    > >Yep, that one seems to be guilty. 2.6.20-rc5 with that commit backed out
    > >survived about 3 hours of testing, while the average was around 5
    > >minutes for a failure, sometimes even before I could log in.
    > >I took a look at the patch, but I can't really tell anything.
    > >nv_adma_check_atapi_dma somehow looks like it should not negate its
    > >return value, so that it returns 0 (atapi dma available) when
    > >adma_enable was 1. But I'm not exactly confident about that either ;)
    > >Will it hurt if I try to remove the negation?
    >
    > It should be correct the way it is - that check is trying to prevent
    > ATAPI commands from using DMA until the slave_config function has been
    > called to set up the DMA parameters properly. When the
    > NV_ADMA_ATAPI_SETUP_COMPLETE flag is not set, this returns 1 which
    > disallows DMA transfers. Unless you were using an ATAPI (i.e. CD/DVD)
    > device on the channel this wouldn't affect you anyway.

    I wondered about it, because the flag is cleared when adma_enabled is 1,
    which seems to be consistent with everything but nv_adma_check_atapi_dma.
    Thus I thought that nv_adma_check_atapi_dma might be wrong, but maybe
    setting/clearing the flag is wrong instead? *feels lost*

    > I'll try your stress test when I get a chance, but I doubt I'll run into
    > the same problem and I haven't seen any similar reports. Perhaps it's
    > some kind of wierd timing issue or incompatibility between the
    > controller and that drive when running in ADMA mode? I seem to remember
    > various reports of issues with certain Maxtor drives and some nForce
    > SATA controllers under Windows at least..

    I just checked Maxtor's knowledge base, that incompatibility does not
    affect my drive.

    Thanks,
    Björn
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