[PATCH 1/3] Documentation:spi:fsl-dspi:add DSPI dma transfer support
broonie at kernel.org
Wed Feb 26 10:38:22 EST 2014
On Wed, Feb 26, 2014 at 10:19:49PM +0800, Shawn Guo wrote:
> On Tue, Feb 25, 2014 at 09:08:30AM +0000, Mark Rutland wrote:
> > > +- use-dma: the bool decide if use dma method in DSPI transfering.
> > Why can the OS not decide this based on the presence of dmas which it
> > can use?
> Yes, OS/driver should decide to use DMA or not, but it shouldn't be
> based on the presence of 'dmas' property. The DMA is a hardware
> resource just like IRQ. It should be just there in client device's node
> as long as the SoC design assigns the channel to the device. The device
> driver should make the decision when DMA should be used, e.g. big amount
> data transfer, and when PIO should be used, e.g. small data.
Right, that's very common - but that decision is usually taken on a per
transfer basis so a DT property would seem odd, especially just a simple
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