On 02/24/2015 04:28 PM, Russell King - ARM Linux wrote:

On Tue, Feb 24, 2015 at 04:21:22PM +0200, Peter Ujfalusi wrote:

quoted

Do not direct map the virtual channels to sDMA request number. When the
sDMA is behind of a crossbar this direct mapping can cause situations when
certain channel can not be requested since the crossbar request number
will no longer match with the sDMA request line.
The direct mapping for virtual channels with HW request lines will make it
harder to implement MEM_TO_MEM mode for the driver.

I assume when you talk about MEM_TO_MEM, you're referring to a DMA_MEMCPY
driver.

mem2mem should not be handled by the slave driver.  This should be a
separate DMA engine driver structure which does not have DMA_SLAVE set.

See how amba-pl08x handles this.

Thanks for the pointer. I'm just planning to add the DMA_MEMCPY support for
omap-dma. With that in place we can convert the remaining legacy API users to
use dmaengine (as I recall all of them are using DMA for memcopy)

-- 
P?ter