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[PATCHv2 13/14] common: DMA-mapping: add WRITE_COMBINE attribute

To: linux-kernel@vger.kernel.org
Subject: [PATCHv2 13/14] common: DMA-mapping: add WRITE_COMBINE attribute
From: Marek Szyprowski <m.szyprowski@samsung.com>
Date: Tue, 27 Mar 2012 15:42:47 +0200
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Thomas Gleixner <tglx@linutronix.de>, Andrew Morton <akpm@linux-foundation.org>, Arnd Bergmann <arnd@arndb.de>, Stephen Rothwell <sfr@canb.auug.org.au>, FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>, microblaze-uclinux@itee.uq.edu.au, linux-arch@vger.kernel.org, x86@kernel.org, linux-sh@vger.kernel.org, linux-alpha@vger.kernel.org, sparclinux@vger.kernel.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mips@linux-mips.org, discuss@x86-64.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linaro-mm-sig@lists.linaro.org, Jonathan Corbet <corbet@lwn.net>, Marek Szyprowski <m.szyprowski@samsung.com>, Kyungmin Park <kyungmin.park@samsung.com>, Andrzej Pietrasiewicz <andrzej.p@samsung.com>, Kevin Cernekee <cernekee@gmail.com>, Dezhong Diao <dediao@cisco.com>, Richard Kuo <rkuo@codeaurora.org>, "David S. Miller" <davem@davemloft.net>, Michal Simek <monstr@monstr.eu>, Guan Xuetao <gxt@mprc.pku.edu.cn>, Paul Mundt <lethal@linux-sh.org>, Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Matt Turner <mattst88@gmail.com>, Tony Luck <tony.luck@intel.com>, Fenghua Yu <fenghua.yu@intel.com>
In-reply-to: <1332855768-32583-1-git-send-email-m.szyprowski@samsung.com>
References: <1332855768-32583-1-git-send-email-m.szyprowski@samsung.com>
Sender: linux-mips-bounce@linux-mips.org
DMA_ATTR_WRITE_COMBINE specifies that writes to the mapping may be
buffered to improve performance. It will be used by the replacement for
ARM/ARV32 specific dma_alloc_writecombine() function.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
---
 Documentation/DMA-attributes.txt |   10 ++++++++++
 include/linux/dma-attrs.h        |    1 +
 2 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt
index b768cc0..811a5d4 100644
--- a/Documentation/DMA-attributes.txt
+++ b/Documentation/DMA-attributes.txt
@@ -31,3 +31,13 @@ may be weakly ordered, that is that reads and writes may 
pass each other.
 Since it is optional for platforms to implement DMA_ATTR_WEAK_ORDERING,
 those that do not will simply ignore the attribute and exhibit default
 behavior.
+
+DMA_ATTR_WRITE_COMBINE
+----------------------
+
+DMA_ATTR_WRITE_COMBINE specifies that writes to the mapping may be
+buffered to improve performance.
+
+Since it is optional for platforms to implement DMA_ATTR_WRITE_COMBINE,
+those that do not will simply ignore the attribute and exhibit default
+behavior.
diff --git a/include/linux/dma-attrs.h b/include/linux/dma-attrs.h
index 71ad34e..ada61e1 100644
--- a/include/linux/dma-attrs.h
+++ b/include/linux/dma-attrs.h
@@ -13,6 +13,7 @@
 enum dma_attr {
        DMA_ATTR_WRITE_BARRIER,
        DMA_ATTR_WEAK_ORDERING,
+       DMA_ATTR_WRITE_COMBINE,
        DMA_ATTR_MAX,
 };
 
-- 
1.7.1.569.g6f426


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