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ARM: 8387/1: arm/mm/dma-mapping.c: Add arm_coherent_dma_mmap

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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.looijmans@topic.nl>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Mike Looijmans 2015-06-03 11:25:31 +01:00 committed by Russell King
parent e001bbae71
commit 55af8a9164
1 changed files with 25 additions and 7 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

32
arch/arm/mm/dma-mapping.c
View file

@ -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,
@ -690,10 +693,7 @@ static void *arm_coherent_dma_alloc(struct device *dev, size_t size,
attrs, __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)
{
@ -704,8 +704,6 @@ 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;
@ -720,6 +718,26 @@ int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma,
return ret;
}
/*
* 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.
*/