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

[Koul, Vinod]

On Wed, 2011-08-10 at 11:32 +0100, Russell King - ARM Linux wrote:
> 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.
Agreed, virtual channels can ensure that channels can be shared
dynamically. If h/w has capability it should be able to do a spi
transfer followed by emmc transfer ans so forth...
Current model of giving client exclusive access to a channel doesn't
allow this

-- 
~Vinod