linux-kernel - [net-next PATCH RFC 20/26] arch/tile: Add option to skip DMA sync as a part of map and unmap

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Date:   Mon, 24 Oct 2016 08:06:12 -0400
From:   Alexander Duyck <alexander.h.duyck@...el.com>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     brouer@...hat.com, Chris Metcalf <cmetcalf@...lanox.com>,
        davem@...emloft.net
Subject: [net-next PATCH RFC 20/26] arch/tile: 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: Chris Metcalf <cmetcalf@...lanox.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
---
 arch/tile/kernel/pci-dma.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/tile/kernel/pci-dma.c b/arch/tile/kernel/pci-dma.c
index 09bb774..24e0f8c 100644
--- a/arch/tile/kernel/pci-dma.c
+++ b/arch/tile/kernel/pci-dma.c
@@ -213,10 +213,12 @@ static int tile_dma_map_sg(struct device *dev, struct scatterlist *sglist,
 
 	for_each_sg(sglist, sg, nents, i) {
 		sg->dma_address = sg_phys(sg);
-		__dma_prep_pa_range(sg->dma_address, sg->length, direction);
 #ifdef CONFIG_NEED_SG_DMA_LENGTH
 		sg->dma_length = sg->length;
 #endif
+		if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
+			continue;
+		__dma_prep_pa_range(sg->dma_address, sg->length, direction);
 	}
 
 	return nents;
@@ -232,6 +234,8 @@ static void tile_dma_unmap_sg(struct device *dev, struct scatterlist *sglist,
 	BUG_ON(!valid_dma_direction(direction));
 	for_each_sg(sglist, sg, nents, i) {
 		sg->dma_address = sg_phys(sg);
+		if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
+			continue;
 		__dma_complete_pa_range(sg->dma_address, sg->length,
 					direction);
 	}
@@ -245,7 +249,8 @@ static dma_addr_t tile_dma_map_page(struct device *dev, struct page *page,
 	BUG_ON(!valid_dma_direction(direction));
 
 	BUG_ON(offset + size > PAGE_SIZE);
-	__dma_prep_page(page, offset, size, direction);
+	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		__dma_prep_page(page, offset, size, direction);
 
 	return page_to_pa(page) + offset;
 }
@@ -256,6 +261,9 @@ static void tile_dma_unmap_page(struct device *dev, dma_addr_t dma_address,
 {
 	BUG_ON(!valid_dma_direction(direction));
 
+	if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
+		return;
+
 	__dma_complete_page(pfn_to_page(PFN_DOWN(dma_address)),
 			    dma_address & (PAGE_SIZE - 1), size, direction);
 }