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    SubjectRe: [BUG] PDC20268 crashing during DMA setup on stock Debian 2.6.12-1-powerpc

    > BusMaster-DMA definitely should be enabled on that card. After a lot
    > of looking through icky IDE code, I've determined that the reason for
    > the crash is that if there is a "mate", or another IDE bus on the
    > same card, then hwif->dma_master is set to hwif->mate->dma_base on
    > the secondary channel. Since DMA explicitly wasn't enabled on the
    > primary channel, hwif->dma_master on the secondary is 0 even though
    > dma is enabled, and therefore we hit that BUG().
    > Therefore it seems that the only issue is ide_get_or_set_dma_base is
    > returning 0 when it should return a valid DMA base. In that
    > function, the only ways that function can even theoretically return 0
    > without printing any weird error messages is "if (hwif->mmio)" or "if
    > (hwif->mate && hwif->mate->dma_base)". The latter can't happen
    > before hwif->mate is set up (since the problem is while initializing
    > the primary). Could hwif->mmio be nonzero somehow? The only drivers
    > that seem to set it are pci/sgiioc4, pci/siimage, ppc/pmac, and a
    > couple misc arch drivers.
    > I see a couple theoretical possibilities:
    > * hwif->mate and hwif->mate->dma_base are set for the primary
    > while still initializing it (before any secondary is set up.
    > * hwif->mmio is set somehow even though it shouldn't be, is the
    > value ever pre-initialized to 0?

    Maybe there is some fighting going on between ppc/pmac.c and that driver
    over the hwif's and you end up with mmio inadvertently set ?

    > > Again, best is you pour printk's all over setup-pci.c and ide-dma.c
    > > to figure out what's going on...
    > I wish I could but the machine is remote and in-production, so it's
    > hard to have time to do much with it. I'm trying as best I can to
    > walk through the sources by hand, specifically with regards to
    > changes between the two. I'm hoping I can come up with a good enough
    > guess by Thanksgiving, so that when I have a week near the server to
    > test things out I can make significant progress.

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      Last update: 2005-10-20 03:42    [W:0.034 / U:187.344 seconds]
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