On Mon, 2012-04-23 at 10:50 +0100, Russell King - ARM Linux wrote: > On Mon, Apr 23, 2012 at 06:40:06PM +0900, Boojin Kim wrote: > > I met a problem on DMA cyclic mode (DMA_CYCLIC) for sound playback. > > Kernel BUG occurs during DMA transfer with DMA cyclic mode. > > This patch makes the cookies into zero. But, cookies should be kept > > during cyclic mode because cyclic mode re-uses the cookies. > > The protection is there to prevent cookies being accidentally re-used. > If you're running a cyclic transfer, even then you shouldn't be completing > the same cookie time and time again - I think Vinod also concurs with this. Right :) I recently committed patch for imx-dma which doesn't mark the cyclic descriptor as complete. Descriptor represents a transaction and makes no sense to complete t if the transaction is still continuing. > > I think our preference is for cyclic transfers to entire remain uncompleted, > or to get a new cookie each time they allegedly "complete". No it is not complete. Cyclic never completes, it aborts when user wants. The "notification" interrupt is for updating the counters/notifying (timestamp/periods elapsed in sound), and shouldn't be used for anything else
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