Messages in this thread | | | Date | Tue, 20 Dec 2011 20:54:02 +0800 | From | Shawn Guo <> | Subject | Re: [PATCH 0/4] Fix the left DMA_NONE from dma_transfer_direction migration |
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On Tue, Dec 20, 2011 at 02:54:04PM +0530, Vinod Koul wrote: > On Tue, 2011-12-13 at 23:48 +0800, Shawn Guo wrote: > > I have been working on -rc recently, and have not noticed the failure > > until I ran next tree today. The mxs-mmc driver is broken on next > > tree because the DMA_NONE was left over from the dma_transfer_direction > > migration for mxs-dma and its client drivers. > > > For DMA transfer, the NONE direction makes no sense? > > In your conetext, what are you trying to achieve? > The mxs-dma controller has a feature to program peripheral registers with given values (mxs-dma PIO mode). This is designed to pipeline the operations. For example, we can put mxs-mmc controller register values into scatter list as one element together with actual data. Triggering the mxs-dma, the dma will program the values into mxs-mmc controller register to set up and enable mxs-mmc, and then dma continue transfer data from/to mxs-mmc. All these get done in one dmaengine_submit().
And DMA_NONE was used to let mxs-dma know this is a PIO operation.
-- Regards, Shawn
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