linux-kernel - [net-next PATCH RFC 03/26] arch/arc: Add option to skip sync on DMA mapping

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Message-ID: <20161024120442.16276.95329.stgit@ahduyck-blue-test.jf.intel.com>
Date:   Mon, 24 Oct 2016 08:04:42 -0400
From:   Alexander Duyck <alexander.h.duyck@...el.com>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     Vineet Gupta <vgupta@...opsys.com>,
        linux-snps-arc@...ts.infradead.org, davem@...emloft.net,
        brouer@...hat.com
Subject: [net-next PATCH RFC 03/26] arch/arc: Add option to skip sync on DMA
 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: Vineet Gupta <vgupta@...opsys.com>
Cc: linux-snps-arc@...ts.infradead.org
Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
---
 arch/arc/mm/dma.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index 20afc65..d0c4b28 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -133,7 +133,8 @@ static dma_addr_t arc_dma_map_page(struct device *dev, struct page *page,
 		unsigned long attrs)
 {
 	phys_addr_t paddr = page_to_phys(page) + offset;
-	_dma_cache_sync(paddr, size, dir);
+	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		_dma_cache_sync(paddr, size, dir);
 	return plat_phys_to_dma(dev, paddr);
 }