On Tue, Mar 15, 2016 at 10:12:11AM +0800, Zhen Lei wrote:
> 1. In swiotlb_alloc_coherent, the branch of __get_free_pages. Directly
> return vaddr on success, and pass vaddr to free_pages on failure.
> 2. So, we can directly transparent pass vaddr from __dma_free to
> swiotlb_free_coherent, keep consistent with swiotlb_alloc_coherent.
>
> This patch have no functional change,
I don't think so.
> but can obtain a bit performance improvement.
Have you actually measured it?
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index a6e757c..b2f2834 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -187,8 +187,6 @@ static void __dma_free(struct device *dev, size_t size,
> void *vaddr, dma_addr_t dma_handle,
> struct dma_attrs *attrs)
> {
> - void *swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle));
> -
> size = PAGE_ALIGN(size);
>
> if (!is_device_dma_coherent(dev)) {
> @@ -196,7 +194,7 @@ static void __dma_free(struct device *dev, size_t size,
> return;
> vunmap(vaddr);
> }
> - __dma_free_coherent(dev, size, swiotlb_addr, dma_handle, attrs);
> + __dma_free_coherent(dev, size, vaddr, dma_handle, attrs);
> }
What happens when !is_device_dma_coherent(dev)? (hint: read two lines
above __dma_free_coherent).
--
Catalin
