On Thu, 2 May 2013, Vinod Koul wrote: > On Tue, Apr 30, 2013 at 02:17:13PM +0200, Guennadi Liakhovetski wrote: > > (added Russell to CC, sorry for not including initially) > > > > Hi Vinod > > > > On Tue, 30 Apr 2013, Vinod Koul wrote: > > > > > On Tue, Apr 30, 2013 at 09:11:19AM +0200, Guennadi Liakhovetski wrote: > > > > Previously an issue has been discussed, arising on sh-/r-mobile > > > > ARM-based > > > > systems. There we typically have multiple DMA controller instances with > > > > exactly equal or very similar capabilities. Each of them can serve the > > > > same > > > > slaves, using the same slave identifiers (request line IDs). With the > > > > present DMA DT implementation _each_ such DMA slave would have to > > > > reference > > > > _each_ of those DMA controllers in its DMA bindings, e.g. > > > But why... if that is the case then we havent define DT-bindings clearly > > > enough > > > > Sorry, what do you mean "why?" Why each slave has to reference each DMA > > controller? We have discussed this A LOT before... My understanding is, > > that we decided, that the sh-/r-mobile case of multiple equal DMA > > controllers is an exception and that we don't want to punish everyone for > > it. So, the design includes only explicit requesting of specific DMA > > request lines on specific DMA controllers, no wild-cards. If a slave DMA > > channel can be provided by several DMA controllers we decided to list them > > all explicitly too. And for the sh-/r-mobile case a DMA-mux DT node has > > been proposed. This is exactly what this patch series is implementing. Is > > my understanding wrong? > > > > > And we havent merged that yet, so why not fix that in first set itself > > > > Sorry, don't understand. The series isn't merged yet, that's right. That's > > why I explicitly mention this dependency here. But this isn't a fix. This > > is a new feature. The first patch-series only touches a specific DMA > > controller driver and relevant platforms. No core changes, so, it's not > > that intrusive and can be applied quickly. Whereas this series affects the > > core and might need a more careful consideration, discussion, etc. > What i mean from above is if we were already defining the sh-DT binding then > why > wasnt this taken care in the orignal definition? > > It would make sense to have proper binding which works well for both of these > case, why a two shot approach?
In the first patch-series we implement DT support in shdma according to the existing API and add DT nodes to a platform. This is already a functioning implementation. The second patch-set is a new feature. It adds a new API - a DMA multiplexer and implementation examples. This way we can clearly show how the new API shall be used - what _changes_ are required to existing DMA DT implementations to support it. I think it makes sense to do this in two steps. Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/