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 at synopsys.com> > Reviewed-by: Catalin Marinas <catalin.marinas at arm.com> > Cc: Marek Szyprowski <m.szyprowski at samsung.com> > Cc: Vineet Gupta <vgupta at synopsys.com> > Cc: <stable at vger.kernel.org> > --- Tested-by: Ramiro Oliveira <Ramiro.Oliveira at synopsys.com>
