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From: "Oskar Schirmer" <os@emlix.com>
To: Michael Hennerich <Michael.Hennerich@analog.com>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>,
	Andrew Morton <akpm@linux-foundation.org>, linux-input@vger.kernel.org,
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	Oliver Schneidewind <osw@emlix.com>, Johannes Weiner <jw@emlix.com>
Subject: [PATCH v2] ad7877: keep dma rx buffers in seperate cache lines
Date: Mon, 10 May 2010 12:34:02 +0200
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diff --git a/drivers/input/touchscreen/ad7877.c b/drivers/input/touchscreen/ad7877.c
index 9cfc8b5..69ebacf 100644
--- a/drivers/input/touchscreen/ad7877.c
+++ b/drivers/input/touchscreen/ad7877.c
@@ -153,15 +153,29 @@ enum {
  */
 
 struct ser_req {
+	u16			sample;
+	/*
+	 * DMA (thus cache coherency maintainance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	char			__padalign[L1_CACHE_BYTES - sizeof(u16)];
+
 	u16			reset;
 	u16			ref_on;
 	u16			command;
-	u16			sample;
 	struct spi_message	msg;
 	struct spi_transfer	xfer[6];
 };
 
 struct ad7877 {
+	u16			conversion_data[AD7877_NR_SENSE];
+	/*
+	 * DMA (thus cache coherency maintainance) requires the
+	 * transfer buffers to live in their own cache lines.
+	 */
+	char			__padalign[L1_CACHE_BYTES
+					- AD7877_NR_SENSE * sizeof(u16)];
+
 	struct input_dev	*input;
 	char			phys[32];
 
@@ -182,8 +196,6 @@ struct ad7877 {
 	u8			averaging;
 	u8			pen_down_acc_interval;
 
-	u16			conversion_data[AD7877_NR_SENSE];
-
 	struct spi_transfer	xfer[AD7877_NR_SENSE + 2];
 	struct spi_message	msg;