netdev - [net-next PATCH RFC 14/26] arch/nios2: Add option to skip DMA sync as a part of map and unmap

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Date:   Mon, 24 Oct 2016 08:05:40 -0400
From:   Alexander Duyck <alexander.h.duyck@...el.com>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     Ley Foon Tan <lftan@...era.com>, davem@...emloft.net,
        brouer@...hat.com
Subject: [net-next PATCH RFC 14/26] arch/nios2: Add option to skip DMA sync
 as a part of map and unmap

This change allows us to pass DMA_ATTR_SKIP_CPU_SYNC which allows us to
avoid invoking cache line invalidation if the driver will just handle it
via a sync_for_cpu or sync_for_device call.

Cc: Ley Foon Tan <lftan@...era.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
---
 arch/nios2/mm/dma-mapping.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/nios2/mm/dma-mapping.c b/arch/nios2/mm/dma-mapping.c
index d800fad..b83e723 100644
--- a/arch/nios2/mm/dma-mapping.c
+++ b/arch/nios2/mm/dma-mapping.c
@@ -102,7 +102,9 @@ static int nios2_dma_map_sg(struct device *dev, struct scatterlist *sg,
 
 		addr = sg_virt(sg);
 		if (addr) {
-			__dma_sync_for_device(addr, sg->length, direction);
+			if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+				__dma_sync_for_device(addr, sg->length,
+						      direction);
 			sg->dma_address = sg_phys(sg);
 		}
 	}
@@ -117,7 +119,9 @@ static dma_addr_t nios2_dma_map_page(struct device *dev, struct page *page,
 {
 	void *addr = page_address(page) + offset;
 
-	__dma_sync_for_device(addr, size, direction);
+	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		__dma_sync_for_device(addr, size, direction);
+
 	return page_to_phys(page) + offset;
 }
 
@@ -125,7 +129,8 @@ static void nios2_dma_unmap_page(struct device *dev, dma_addr_t dma_address,
 		size_t size, enum dma_data_direction direction,
 		unsigned long attrs)
 {
-	__dma_sync_for_cpu(phys_to_virt(dma_address), size, direction);
+	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		__dma_sync_for_cpu(phys_to_virt(dma_address), size, direction);
 }
 
 static void nios2_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
@@ -138,6 +143,9 @@ static void nios2_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
 	if (direction == DMA_TO_DEVICE)
 		return;
 
+	if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
+		return;
+
 	for_each_sg(sg, sg, nhwentries, i) {
 		addr = sg_virt(sg);
 		if (addr)