Sebastian Frias <sf84@xxxxxxxxxxx> writes: > On 09/12/16 07:59, Vinod Koul wrote: >> On Thu, Dec 08, 2016 at 04:48:18PM +0000, Måns Rullgård wrote: >>> Vinod Koul <vinod.koul@xxxxxxxxx> writes: >>> >>>> To make it efficient, disregarding your Sbox HW issue, the solution is >>>> virtual channels. You can delink physical channels and virtual channels. If >>>> one has SW controlled MUX then a channel can service any client. For few >>>> controllers request lines are hard wired so they cant use any channel. But >>>> if you dont have this restriction then driver can queue up many transactions >>>> from different controllers. >>> >>> Have you been paying attention at all? This exactly what the driver >>> ALREADY DOES. >> >> And have you read what the question was? I wrote the driver. I think I know what Mason and I are asking. > I think many people appreciate the quick turn around time and > responsiveness of knowledgeable people making constructive remarks in > this thread, but it looks we are slowly drifting away from the main > problem. > > If we had to sum up the discussion, the current DMA API/framework in > Linux seems to lack a way to properly handle this HW (or if it has a > way, the information got lost somewhere). > > What concrete solution do you propose? > > Alternatively, one can think of the current issue (i.e.: the fact that > the IRQ arrives "too soon") in a different way. Instead of thinking > the IRQ indicates "transfer complete", it is indicating "ready to > accept another command", which in practice (and with proper API > support) can translate into efficient queuing of DMA operations. For multiple back to back transfers to the same peripheral, it is indeed a slight optimisation. What's apparently lacking is some way of doing a full flush at the end of a series of transfers, before switching the channel to another device. -- Måns Rullgård -- 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
