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    SubjectRe: DAC960 in 2.5.38, with new changes
    >>>>> On Tue, 24 Sep 2002 10:28:43 -0700, Dave Olien <dmo@osdl.org> said:

    Dave> Hmm, interesting. A big part of what I'm doing to the driver
    Dave> right now is plugging in calls to the PCI DMA interfaces.

    That's fine (actually, it's more than that: it's great!).

    Dave> So unless the underlying implementation is aware of these
    Dave> platform limitations and "doing the right thing", I'm adding
    Dave> a bunch of bounce buffer activity for many ia64 platforms.
    Dave> That would be too bad.

    The idea is to do something along these lines:

    o Use PCA DMA interface for managing all DMA buffers.

    o If sizeof(dma_addr_t) > 4, turn on DAC mode and call
    pci_set_dma_mask(dev, MAX_ADDR), where MAX_ADDR is the maximum
    address that can be reached by the controller (i.e.,
    0xffffffffffffffff for a truly 64-bit-capable PCI controller).

    This way, everything should work out correctly and with good
    performance on all imaginable platforms (ia64 with and without
    hardware I/O TLB, plain x86, x86 with >4GB RAM, SPARC64 with 32-bit
    dma_addr_t, etc.).

    --david
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