On Fri, Apr 11, 2014 at 03:23:54PM +0300, Peter Ujfalusi wrote: > On 04/11/2014 02:31 PM, Vinod Koul wrote: > > >> I would say that it is channel based config. I don't see the reason why would > >> one mix different priorities on a configured channel between descriptors. > >> > >>> If not then we can add this in dma_slave_config ? > >> > >> So adding to the struct for example: > >> bool high_priority; > > > > In designware controller, we can have channel priorties from 0 to 7 which IIRC 7 > > being highest. So bool wont work. unsigned int/u8 would be good. > > I see. But from a generic code what number should one pass if we want to get > the highest priority? With eDMA3 we essentially have three levels (see later) > so if we receive 7 as priority what shall we do? Just treat as highest? But if > we receive 4, which is somewhere in the middle for designware it is still > means highest for us. > > I see this too small step partitioning in common code a bit problematic when > it comes to how to interpret the 'magic numbers'. > Also how all the driver in the system will decide the priority number? I'm > sure they will pick something conveniently average for themselves and I > imagine audio would try to pick something which is bigger than the numbers > others have taken... > > > How about your controller, is it binary? > > We also have priority from 0 to 7, 0 being the highest priority. We have 3 > Transfer Controllers/Event Queues and we can set the priority for the TC/EQ > and assign the given channel to the desired TC/EQ. > So in reality we have 3 priorities to choose from in my view since we only > have 3 TC/EQ in eDMA3 (of AM335x/AM447x) on other SoCs we can have different > number of TC/EQ. I think the number shouldn't be viewed in absolute terms. If we decide that (lets say) 0-7, then any controller should map 0 to lowest and 7 to highest. For your case you can do this and then intermediate numbers would be medium priority. Such a system might work well... Also how would a client driver know which priority to use? Would it come from DT? -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
