Messages in this thread | | | Date | Thu, 22 Mar 2012 11:00:37 +0100 | From | Rafal Prylowski <> | Subject | Re: [PATCH] ep93xx: Implement double buffering for M2M DMA channels |
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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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