On Tuesday 20 January 2015 01:44:38 Kuninori Morimoto wrote: > From: Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx> > > Current Renesas Audio DMAC Peri Peri driver is based on > SH_DMAE_BASE driver which is used for Renesas SH-Mobile. > But, basically, SH_DMAE_BASE driver was created for > SuperH SoC, and it is not fully cared for DT. > > For example, current SH_DMAE_BASE base driver will return > non-matching DMA channel if some non-SH_DMAE_BASE drivers > are probed. > So, sound driver will get wrong DMA channel > if Audio DMAC (= rcar-dma) was not probed, > but Audio DMAC Peri Peri (= SH_DMAE_BASE) was probed. > > OTOH, many SH-Mobile series drivers are using SH_DMAE_BASE > driver, and Renesas R-Car series will not use it anymore. > Maintenance cost for fully cared DT support on SH_DMAE_BASE > will be very high > (and keeping compatibility will be very complex). > > In addition, Audio DMAC Peri Peri itself is very simple device, > and, no SoC/board is using it from non-DT environment. > > This patch simply removes current rcar-audmapp driver. > I'm confused by the description above. From what I understand, the purpose of the SH_DMAE_BASE driver is to multiplex between the DMA engines that all share the same slaves on some of the shmobile/r-mobile/r-car chips. If the audma driver does not share its slaves with another dmaengine, it needs to register its own of_dma_controller, which it does. The problem you describe with getting the wrong channel seems to me that the shdma_chan_filter() function matches any DMA engine that was registered through shdma_init(), because its device_alloc_chan_resources function pointer matches. This problem could be avoided by adding some flag in shdma_dev as a bug-fix (also for backports to stable kernels). That said, together with patch 2, this seems like a useful simplification, it just needs a better description in my mind. Arnd -- 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
