Messages in this thread | | | Subject | Re: [PATCH v2] arc: Implement arch-specific dma_map_ops.mmap | From | Ramiro Oliveira <> | Date | Tue, 15 Nov 2016 15:45:35 +0000 |
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On 11/3/2016 3:06 PM, Alexey Brodkin wrote: > We used to use generic implementation of dma_map_ops.mmap which is > dma_common_mmap() but that only worked for simpler cached mappings when > vaddr = paddr. > > If a driver requests uncached DMA buffer kernel maps it to virtual > address so that MMU gets involved and page uncached status takes into > account. In that case usage of dma_common_mmap() lead to mapping of > vaddr to vaddr for user-space which is obviously wrong. For more detals > please refer to verbose explanation here [1]. > > So here we implement our own version of mmap() which always deals > with dma_addr and maps underlying memory to user-space properly > (note that DMA buffer mapped to user-space is always uncached > because there's no way to properly manage cache from user-space). > > [1] https://lkml.org/lkml/2016/10/26/973 > > Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> > Cc: Marek Szyprowski <m.szyprowski@samsung.com> > Cc: Vineet Gupta <vgupta@synopsys.com> > Cc: <stable@vger.kernel.org> > ---
Tested-by: Ramiro Oliveira <Ramiro.Oliveira@synopsys.com>
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