linux-kernel - [PATCH 1/1] arm64/dma-mapping: remove an unnecessary conversion

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Date:	Tue, 15 Mar 2016 10:12:11 +0800
From:	Zhen Lei <thunder.leizhen@...wei.com>
To:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>
CC:	Zefan Li <lizefan@...wei.com>, Xinwei Hu <huxinwei@...wei.com>,
	"Tianhong Ding" <dingtianhong@...wei.com>,
	Hanjun Guo <guohanjun@...wei.com>,
	Zhen Lei <thunder.leizhen@...wei.com>
Subject: [PATCH 1/1] arm64/dma-mapping: remove an unnecessary conversion

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, but can obtain a bit performance
improvement.

Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
---
 arch/arm64/mm/dma-mapping.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

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);
 }

 static dma_addr_t __swiotlb_map_page(struct device *dev, struct page *page,
--
2.5.0