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由 Mike Looijmans 提交于
When dma-coherent transfers are enabled, the mmap call must not change the pg_prot flags in the vma struct. Split the arm_dma_mmap into a common and specific parts, and add a "arm_coherent_dma_mmap" implementation that does not alter the page protection flags. Tested on a topic-miami board (Zynq) using the ACP port to transfer data between FPGA and CPU using the Dyplo framework. Without this patch, byte-wise access to mmapped coherent DMA memory was about 20x slower because of the memory being marked as non-cacheable, and transfer speeds would not exceed 240MB/s. After this patch, the mapped memory is cacheable and the transfer speed is again 600MB/s (limited by the FPGA) when the data is in the L2 cache, while data integrity is being maintained. The patch has no effect on non-coherent DMA. Signed-off-by: NMike Looijmans <mike.looijmans@topic.nl> Acked-by: NArnd Bergmann <arnd@arndb.de> Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
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