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 boolean.
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