On 15 Jun 11 10:36, Marek Szyprowski wrote: > Hello, > > On Tuesday, June 14, 2011 10:42 PM Arnd Bergmann wrote: > > > On Tuesday 14 June 2011 20:58:25 Zach Pfeffer wrote: > > > I've seen this split bank allocation in Qualcomm and TI SoCs, with > > > Samsung, that makes 3 major SoC vendors (I would be surprised if > > > Nvidia didn't also need to do this) - so I think some configurable > > > method to control allocations is necessarily. The chips can't do > > > decode without it (and by can't do I mean 1080P and higher decode is > > > not functionally useful). Far from special, this would appear to be > > > the default. We at Qualcomm have some platforms that have memory of different performance characteristics, some drivers will need a way of specifying that they need fast memory for an allocation (and would prefer an error if it is not available rather than a fallback to slower memory). It would also be bad if allocators who don't need fast memory got it "accidentally", depriving those who really need it. > > > > Thanks for the insight, that's a much better argument than 'something > > may need it'. Are those all chips without an IOMMU or do we also > > need to solve the IOMMU case with split bank allocation? > > > > I think I'd still prefer to see the support for multiple regions split > > out into one of the later patches, especially since that would defer > > the question of how to do the initialization for this case and make > > sure we first get a generic way. > > > > You've convinced me that we need to solve the problem of allocating > > memory from a specific bank eventually, but separating it from the > > one at hand (contiguous allocation) should help getting the important > > groundwork in at first. > > > > The possible conflict that I still see with per-bank CMA regions are: > > > > * It completely destroys memory power management in cases where that > > is based on powering down entire memory banks. > > I don't think that per-bank CMA regions destroys memory power management > more than the global CMA pool. Please note that the contiguous buffers > (or in general dma-buffers) right now are unmovable so they don't fit > well into memory power management. We also have platforms where a well-defined part of the memory can be powered off, and other parts can't (or won't). We need a way to steer the place allocations come from to the memory that won't be turned off (so that CMA allocations are not an obstacle to memory hotremove). > > Best regards > -- > Marek Szyprowski > Samsung Poland R&D Center > > > > _______________________________________________ > Linaro-mm-sig mailing list > Linaro-mm-sig@xxxxxxxxxxxxxxxx > http://lists.linaro.org/mailman/listinfo/linaro-mm-sig Larry Bassel -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
