On 7/14/2012 6:53 AM, Clark, Rob wrote:
On Fri, Jul 13, 2012 at 1:01 PM, Laura Abbott lauraa@codeaurora.org wrote:
There are currently no dma allocation APIs that support cached buffers. For some use cases, caching provides a signficiant performance boost that beats write-combining regions. Add apis to allocate and map a cached DMA region.
btw, there were recent patches for allocating dma memory without a virtual mapping. With this you could map however you want to userspace (for example, cached)
I'm assuming that you are not needing it to be mapped cached to kernel?
Thanks for reminding me about those patches. They don't quite solve the problem as is for two reasons: 1) I'm looking at regular CMA allocations, not iommu allocations which is what the patches covered 2) I do actually need a kernel cached mapping in addition to the userspace mappings.
I've obviously missed the last DMA rework patches, and I should rebase/rework against those. Is another DMA attribute (DMA_ATTR_CACHED) an acceptable option?
BR, -R
Thanks, Laura
Signed-off-by: Laura Abbott lauraa@codeaurora.org
arch/arm/include/asm/dma-mapping.h | 21 +++++++++++++++++++++ arch/arm/mm/dma-mapping.c | 21 +++++++++++++++++++++ 2 files changed, 42 insertions(+), 0 deletions(-)
diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h index dc988ff..1565403 100644 --- a/arch/arm/include/asm/dma-mapping.h +++ b/arch/arm/include/asm/dma-mapping.h @@ -239,12 +239,33 @@ int dma_mmap_coherent(struct device *, struct vm_area_struct *, extern void *dma_alloc_writecombine(struct device *, size_t, dma_addr_t *, gfp_t);
+/**
- dma_alloc_cached - allocate cached memory for DMA
- @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
- @size: required memory size
- @handle: bus-specific DMA address
- Allocate some cached memory for a device for
- performing DMA. This function allocates pages, and will
- return the CPU-viewed address, and sets @handle to be the
- device-viewed address.
- */
+extern void *dma_alloc_cached(struct device *, size_t, dma_addr_t *,
gfp_t);- #define dma_free_writecombine(dev,size,cpu_addr,handle) \ dma_free_coherent(dev,size,cpu_addr,handle)
+#define dma_free_cached(dev,size,cpu_addr,handle) \
dma_free_coherent(dev,size,cpu_addr,handle)int dma_mmap_writecombine(struct device *, struct vm_area_struct *, void *, dma_addr_t, size_t);
+int dma_mmap_cached(struct device *, struct vm_area_struct *,
void *, dma_addr_t, size_t);- /*
- This can be called during boot to increase the size of the consistent
- DMA region above it's default value of 2MB. It must be called before the
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index b1911c4..f396ddc 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -633,6 +633,20 @@ dma_alloc_writecombine(struct device *dev, size_t size, dma_addr_t *handle, gfp_ } EXPORT_SYMBOL(dma_alloc_writecombine);
+/*
- Allocate a cached DMA region
- */
+void * +dma_alloc_cached(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp) +{
return __dma_alloc(dev, size, handle, gfp,pgprot_kernel,__builtin_return_address(0));+} +EXPORT_SYMBOL(dma_alloc_cached);
- static int dma_mmap(struct device *dev, struct vm_area_struct *vma, void *cpu_addr, dma_addr_t dma_addr, size_t size) {
@@ -664,6 +678,13 @@ int dma_mmap_writecombine(struct device *dev, struct vm_area_struct *vma, } EXPORT_SYMBOL(dma_mmap_writecombine);
+int dma_mmap_cached(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, dma_addr_t dma_addr, size_t size)+{
return dma_mmap(dev, vma, cpu_addr, dma_addr, size);+} +EXPORT_SYMBOL(dma_mmap_cached);
/*
- Free a buffer as defined by the above mapping.
-- 1.7.8.3
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