[PATCH v3 3/3] i2c-designware: Allow mixed endianness accesses

[Jean-Hugues Deschenes <jean-hugues.deschenes-YGVykHU+fedBDgjK7y7TUQ@public.gmane.org>]

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Allows CPUs of a given endianness to access a dw controller of a different
endianness. Endianncess difference is detected at run time through the dw
component type register.

Signed-off-by: Jean-Hugues Deschenes <jean-hugues.deschenes-YGVykHU+fedBDgjK7y7TUQ@public.gmane.org>

---
 drivers/i2c/busses/i2c-designware.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

Index: linux-2.6_i2c/drivers/i2c/busses/i2c-designware.c
===================================================================
--- linux-2.6_i2c.orig/drivers/i2c/busses/i2c-designware.c
+++ linux-2.6_i2c/drivers/i2c/busses/i2c-designware.c
@@ -36,6 +36,7 @@
 #include <linux/interrupt.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
+#include <linux/swab.h>
 
 /*
  * Registers offset
@@ -192,6 +193,7 @@ static char *abort_sources[] = {
  * @status: i2c master status, one of STATUS_*
  * @abort_source: copy of the TX_ABRT_SOURCE register
  * @irq: interrupt number for the i2c master
+ * @swab: true if the instantiated IP is of different endianess
  * @adapter: i2c subsystem adapter node
  * @tx_fifo_depth: depth of the hardware tx fifo
  * @rx_fifo_depth: depth of the hardware rx fifo
@@ -215,6 +217,7 @@ struct dw_i2c_dev {
 	unsigned int		status;
 	u32			abort_source;
 	int			irq;
+	int			swab;
 	struct i2c_adapter	adapter;
 	unsigned int		tx_fifo_depth;
 	unsigned int		rx_fifo_depth;
@@ -222,11 +225,19 @@ struct dw_i2c_dev {
 
 static u32 dw_readl(struct dw_i2c_dev *dev, int offset)
 {
-	return readl(dev->base + offset);
+	u32 value = readl(dev->base + offset);
+
+	if (dev->swab)
+		return swab32(value);
+	else
+		return value;
 }
 
 static void dw_writel(struct dw_i2c_dev *dev, u32 b, int offset)
 {
+	if (dev->swab)
+		b = swab32(b);
+
 	writel(b, dev->base + offset);
 }
 
@@ -759,7 +770,9 @@ static int __devinit dw_i2c_probe(struct
 	}
 
 	reg = dw_readl(dev, DW_IC_COMP_TYPE);
-	if (reg != 0x44570140) {
+	if (reg == ___constant_swab32(0x44570140))
+		dev->swab = 1;
+	else if (reg != 0x44570140) {
 		dev_err(&pdev->dev, "Unknown Synopsys component type: "
 				"0x%08x\n",	reg);
 		r = -ENODEV;

--