linux-kernel - [net-next PATCH RFC 09/26] arch/hexagon: Add option to skip DMA sync as a part of mapping

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Message-ID: <20161024120513.16276.39929.stgit@ahduyck-blue-test.jf.intel.com>
Date:   Mon, 24 Oct 2016 08:05:14 -0400
From:   Alexander Duyck <alexander.h.duyck@...el.com>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     linux-hexagon@...r.kernel.org, brouer@...hat.com,
        davem@...emloft.net, Richard Kuo <rkuo@...eaurora.org>
Subject: [net-next PATCH RFC 09/26] arch/hexagon: Add option to skip DMA
 sync as a part of mapping

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
later via a sync_for_cpu or sync_for_device call.

Cc: Richard Kuo <rkuo@...eaurora.org>
Cc: linux-hexagon@...r.kernel.org
Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
---
 arch/hexagon/kernel/dma.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/hexagon/kernel/dma.c b/arch/hexagon/kernel/dma.c
index b901778..dbc4f10 100644
--- a/arch/hexagon/kernel/dma.c
+++ b/arch/hexagon/kernel/dma.c
@@ -119,6 +119,9 @@ static int hexagon_map_sg(struct device *hwdev, struct scatterlist *sg,
 
 		s->dma_length = s->length;
 
+		if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
+			continue;
+
 		flush_dcache_range(dma_addr_to_virt(s->dma_address),
 				   dma_addr_to_virt(s->dma_address + s->length));
 	}
@@ -180,7 +183,8 @@ static dma_addr_t hexagon_map_page(struct device *dev, struct page *page,
 	if (!check_addr("map_single", dev, bus, size))
 		return bad_dma_address;
 
-	dma_sync(dma_addr_to_virt(bus), size, dir);
+	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		dma_sync(dma_addr_to_virt(bus), size, dir);
 
 	return bus;
 }