i2c-designware: Allow mixed endianness accesses

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 <[email protected]>
Signed-off-by: Dirk Brandewie <[email protected]>
Signed-off-by: Ben Dooks <[email protected]>

drivers/i2c/busses/i2c-designware.c

@@ -37,6 +37,7 @@
 #include <linux/platform_device.h>
 #include <linux/io.h>
 #include <linux/slab.h>
+#include <linux/swab.h>
 
 /*
  * Registers offset
@@ -193,6 +194,7 @@ 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
@@ -216,18 +218,27 @@ 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;
 };
 
 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);
 }
 
@@ -760,7 +771,9 @@ static int __devinit dw_i2c_probe(struct platform_device *pdev)
 	}
 
 	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;