On Wed, Jul 23, 2014 at 02:35:06AM +0100, Laura Abbott wrote:
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -298,37 +298,19 @@ static void *
> __dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
> const void *caller)
> {
> - struct vm_struct *area;
> - unsigned long addr;
> -
> /*
> * DMA allocation can be mapped to user space, so lets
> * set VM_USERMAP flags too.
> */
> - area = get_vm_area_caller(size, VM_ARM_DMA_CONSISTENT | VM_USERMAP,
> - caller);
> - if (!area)
> - return NULL;
> - addr = (unsigned long)area->addr;
> - area->phys_addr = __pfn_to_phys(page_to_pfn(page));
> -
> - if (ioremap_page_range(addr, addr + size, area->phys_addr, prot)) {
> - vunmap((void *)addr);
> - return NULL;
> - }
> - return (void *)addr;
> + return dma_common_contiguous_remap(page, size,
> + VM_ARM_DMA_CONSISTENT | VM_USERMAP,
> + prot, caller);
I think we still need at least a comment in the commit log since the arm
code is moving from ioremap_page_range() to map_vm_area(). There is a
slight performance penalty with the addition of a kmalloc() on this
path.
Or even better (IMO), see below.
> --- a/drivers/base/dma-mapping.c
> +++ b/drivers/base/dma-mapping.c
[...]
> +void *dma_common_contiguous_remap(struct page *page, size_t size,
> + unsigned long vm_flags,
> + pgprot_t prot, const void *caller)
> +{
> + int i;
> + struct page **pages;
> + void *ptr;
> +
> + pages = kmalloc(sizeof(struct page *) << get_order(size), GFP_KERNEL);
> + if (!pages)
> + return NULL;
> +
> + for (i = 0; i < (size >> PAGE_SHIFT); i++)
> + pages[i] = page + i;
> +
> + ptr = dma_common_pages_remap(pages, size, vm_flags, prot, caller);
> +
> + kfree(pages);
> +
> + return ptr;
> +}
You could avoid the dma_common_page_remap() here (and kmalloc) and
simply use ioremap_page_range(). We know that
dma_common_contiguous_remap() is only called with contiguous physical
range, so ioremap_page_range() is suitable. It also makes it a
non-functional change for arch/arm.
--
Catalin
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