[v3] ad7877: keep dma rx buffers in seperate cache lines

Commit Message

Oskar Schirmer May 10, 2010, 10:42 a.m. UTC

None

Patch

diff --git a/drivers/input/touchscreen/ad7877.c b/drivers/input/touchscreen/ad7877.c
index 885354c..9ebb1b4 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 maintenance) 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 maintenance) 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;