On 09/12/2016 18:17, Vinod Koul wrote: > On Fri, Dec 09, 2016 at 11:25:57AM +0100, Sebastian Frias wrote: >> >> What concrete solution do you propose? > > I have already proposed two solutions. > > A) Request a channel only when you need it. Obviously we can't do virtual > channels with this (though we should still use virt-channels framework). > The sbox setup and teardown can be done as part of channel request and > freeup. PL08x already does this. > > Downside is that we can only have as many consumers at a time as channels. > > I have not heard any technical reason for not doing this apart from drivers > grab the channel at probe, which is incorrect and needs to be fixed > irrespective of the problem at hand. > > This is my preferred option. There is one important drawback with this solution. If a driver calls dma_request_chan() when no channels are currently available, it will get -EBUSY. If there were a flag in dma_request_chan to be put to sleep (with timeout) until a channel is available, then it would work. But busy waiting in the client driver is a waste of power. Regards. -- 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
