[PATCH] DMAEngine: sirf: let the users be able to pause and resume specific buffer

Vinod Koul vinod.koul at intel.com
Mon Jul 29 02:08:19 EDT 2013

On Mon, Jul 29, 2013 at 10:14:24AM +0800, Barry Song wrote:
> 2013/7/4 Barry Song <Baohua.Song at csr.com>
well the submitter didn't cc me. So this wasnt in my INBOX!

> >
> > From: Qipan Li <Qipan.Li at csr.com>
> >
> > this patch adds a buffer_index in pause and resume entries, then users
> > can pause and resume a buffer they want, but don't pause the whole dma.
> >
> > a typical application scenerios is Ping-Pang in two buffers:
typo, pong	          		^^^^^^^^^
> > at the beginning, we enable buf1 and buf2 to receive dma data, after
> > buf1 is full, we pause buf1 and handle the data in this buffer to avoid
> > overflow in buf1. but at the same time, dma is still tranferring in buf2.
> > once we have finished data process in buf1, we enable buf1 again.
> > this will maximize the chance of dma transferring. users pause buf1 by:
> > dmaengine_device_control(sirfport->rx_dma_chan, DMA_PAUSE, 1);
> > users pause buf2 by:
> > dmaengine_device_control(sirfport->rx_dma_chan, DMA_PAUSE, 2);
> > users can still pause the whole dma transferring by dmaengine_pause().
Well this is odd, the second arg is not supposed to be valid for PAUSE op. And
PAUSE means you pause the whole channel.

The above can be done by 
a) have two buffers:
	- prepare first and submit, and start
	- while first is ongoing, prepare second and start
	- first is completed, so you start processing that while second is
	  getting DMAed
	- when processing is completed, submit first again
	- when second is completed, start processing that and submit that once

b) have multiple buffers, A, B, C & D and redo above schema.

Since patch is not the right approach and doesnt use API correctly NAK from me on that


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