Hi Geert > > ...which is in fact the exact same problem that the IOMMU code has - > > might it make sense to give of_dma_request_slave_channel() similar > > (optional?) driver_deferred_probe_check_state() logic, i.e. "if my DMAC > > driver's not shown up by this point, assume it's not built-in and go on > > without it". Of course it is somewhat easier for IOMMU drivers as > > there's zero chance of those popping up as modules later on. > > It may solve the issue in some cases. But only if the dmac is reprobed > before the DMA slave driver, which is not guaranteed. > > BTW, it seems e.g. i2c and serial suffer from the same problem, and fall > back to PIO. However, these drivers try to obtain the DMA channel when > used, not during probe, so they start using DMA after the dmac has been > probed successfully. Actually sound driver get DMA channel when used. But checking DMA availability when probe timing (= try to get, and release it soon). sound driver side other approach is that it don't check it when probe. Best regards --- Kuninori Morimoto
