[Linaro-mm-sig] [PATCH][RFC] arm: dma-mapping: Add support for allocating/mapping cached buffers

[Clark, Rob]

On Fri, Jul 13, 2012 at 1:01 PM, Laura Abbott <lauraa at 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?

BR,
-R

> Signed-off-by: Laura Abbott <lauraa at 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
>
>
> _______________________________________________
> Linaro-mm-sig mailing list
> Linaro-mm-sig at lists.linaro.org
> http://lists.linaro.org/mailman/listinfo/linaro-mm-sig