On Fri, Mar 03, 2017 at 10:50:20AM -0800, Laura Abbott wrote: > On 03/03/2017 08:41 AM, Laurent Pinchart wrote: > > Hi Laura, > > > > Thank you for the patch. > > > > On Thursday 02 Mar 2017 13:44:42 Laura Abbott wrote: > >> When CMA was first introduced, its primary use was for DMA allocation > >> and the only way to get CMA memory was to call dma_alloc_coherent. This > >> put Ion in an awkward position since there was no device structure > >> readily available and setting one up messed up the coherency model. > >> These days, CMA can be allocated directly from the APIs. Switch to using > >> this model to avoid needing a dummy device. This also avoids awkward > >> caching questions. > > > > If the DMA mapping API isn't suitable for today's requirements anymore, I > > believe that's what needs to be fixed, instead of working around the problem > > by introducing another use-case-specific API. > > > > I don't think this is a usecase specific API. CMA has been decoupled from > DMA already because it's used in other places. The trying to go through > DMA was just another layer of abstraction, especially since there isn't > a device available for allocation. Also, we've had separation of allocation and dma-mapping since forever, that's how it works almost everywhere. Not exactly sure why/how arm-soc ecosystem ended up focused so much on dma_alloc_coherent. I think separating allocation from dma mapping/coherency is perfectly fine, and the way to go. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
