Re: [PATCH 0/4] Fix the left DMA_NONE from dma_transfer_direction migration

[Shawn Guo <shawn.guo@freescale.com>]

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