[PATCH] arm/mm/dma-mapping.c: Add arm_coherent_dma_mmap
mike.looijmans at topic.nl
Thu May 7 05:07:25 PDT 2015
Oops, "arch/arm/boot/dts/topic-dyplo.dtsi" should not have been in there. Will
send a v2 patch to correct that.
On 07-05-15 14:00, Mike Looijmans wrote:
> 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
> The patch has no effect on non-coherent DMA.
> Signed-off-by: Mike Looijmans <mike.looijmans at topic.nl>
> arch/arm/boot/dts/topic-dyplo.dtsi | 1 +
> arch/arm/mm/dma-mapping.c | 32 +++++++++++++++++++++++++-------
> 2 files changed, 26 insertions(+), 7 deletions(-)
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