On Tue, Feb 11, 2014 at 05:34:49AM +0000, Yao Yuan wrote:

Here I also have a confusion.
IRQ is must. But DMA isn't very necessary.
How to deal with if one board is need DMA but another is not need?
You mean if DMA is be support once all of them must use dma as first?

That's the point.  Why whether using DMA or not is a board decision?
The DMA resource should be defined at SoC level from the beginning
just like IO and interrupt resource.  And using DMA or PIO should be a
decision made by device driver not device tree.

Shawn