[PATCH V2 6/6] spi/spi-pl022: Request/free DMA channels as and when required.

[Russell King - ARM Linux]

On Wed, Aug 10, 2011 at 03:44:13PM +0530, viresh kumar wrote:
> On 08/10/2011 03:31 PM, Koul, Vinod wrote:
> > And on your patch, are you able to dynamically assign the channels for
> > platform? What is the intended usage? (as Russell articulated it is bad
> > to dynamically assign channel for something like uart)
> 
> Are you talking about channels or DMA request lines? For channels yes,
> we can always allocate channels as they are independent of peripherals.
> About request lines, they are muxed in our case between several
> peripherals, but support for that has to be added in dw_dmac.

Right, and when you do, you'll probably have to go to a virtual channel
implementation, which solves the problem of keeping a channel allocated
and makes this patch redundant.

I assert that any DMA engine implementation where request signals can
be assigned dynamically to DMA channels should be using a virtual channel
implementation.