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
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