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    SubjectRe: [PATCH] ep93xx: Implement double buffering for M2M DMA channels
    On 2012-03-22 01:57, Ryan Mallon wrote:
    > I haven't looked through the patch yet, since I'm waiting on more
    > information from Mika and Hartley's testing.
    > However, the commit log doesn't tell me why we want this change. Is it a
    > performance improvement? If so, do you have some numbers that we can
    > paste into the commit log?

    In principle, using double buffering should be faster than using only
    one buffer and disabling/enabling channel each time. But my measurements
    doesn't show any significant change.

    The real reason for this change is that current code is not 100% reliable
    in IDE-DMA (I'm planning to submit ep93xx ide driver to linux-ide soon).
    Although using only one buffer and DONE interrupt is simple, surprisingly
    we can get interrupt when M2M DMA is in DMA_BUF_ON and DMA_STALL state.
    If we disable the channel at this moment, we end with ata timeout.

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