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: Mike Looijmans <mike.looijm...@topic.nl> --- arch/arm/boot/dts/topic-dyplo.dtsi | 1 + arch/arm/mm/dma-mapping.c | 32 +++++++++++++++++++++++++------- 2 files changed, 26 insertions(+), 7 deletions(-) diff --git a/arch/arm/boot/dts/topic-dyplo.dtsi b/arch/arm/boot/dts/topic-dyplo.dtsi index 0deedb6..fa5901b 100644 --- a/arch/arm/boot/dts/topic-dyplo.dtsi +++ b/arch/arm/boot/dts/topic-dyplo.dtsi @@ -6,5 +6,6 @@ reg = <0x64400000 0x200000>; interrupt-parent = <&gic>; interrupts = <0 57 0x4>; + dma-coherent; }; }; diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 903dba0..4815259 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -148,11 +148,14 @@ static void *arm_coherent_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp, struct dma_attrs *attrs); static void arm_coherent_dma_free(struct device *dev, size_t size, void *cpu_addr, dma_addr_t handle, struct dma_attrs *attrs); +static int arm_coherent_dma_mmap(struct device *dev, struct vm_area_struct *vma, + void *cpu_addr, dma_addr_t dma_addr, size_t size, + struct dma_attrs *attrs); struct dma_map_ops arm_coherent_dma_ops = { .alloc = arm_coherent_dma_alloc, .free = arm_coherent_dma_free, - .mmap = arm_dma_mmap, + .mmap = arm_coherent_dma_mmap, .get_sgtable = arm_dma_get_sgtable, .map_page = arm_coherent_dma_map_page, .map_sg = arm_dma_map_sg, @@ -677,10 +680,7 @@ static void *arm_coherent_dma_alloc(struct device *dev, size_t size, __builtin_return_address(0)); } -/* - * Create userspace mapping for the DMA-coherent memory. - */ -int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma, +static int __arm_dma_mmap(struct device *dev, struct vm_area_struct *vma, void *cpu_addr, dma_addr_t dma_addr, size_t size, struct dma_attrs *attrs) { @@ -691,8 +691,6 @@ int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma, unsigned long pfn = dma_to_pfn(dev, dma_addr); unsigned long off = vma->vm_pgoff; - vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot); - if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret)) return ret; @@ -708,6 +706,26 @@ int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma, } /* + * Create userspace mapping for the DMA-coherent memory. + */ +static int arm_coherent_dma_mmap(struct device *dev, struct vm_area_struct *vma, + void *cpu_addr, dma_addr_t dma_addr, size_t size, + struct dma_attrs *attrs) +{ + return __arm_dma_mmap(dev, vma, cpu_addr, dma_addr, size, attrs); +} + +int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma, + void *cpu_addr, dma_addr_t dma_addr, size_t size, + struct dma_attrs *attrs) +{ +#ifdef CONFIG_MMU + vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot); +#endif /* CONFIG_MMU */ + return __arm_dma_mmap(dev, vma, cpu_addr, dma_addr, size, attrs); +} + +/* * Free a buffer as defined by the above mapping. */ static void __arm_dma_free(struct device *dev, size_t size, void *cpu_addr, -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/