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 <jean-hugues.deschenes@octasic.com>
Signed-off-by: Dirk Brandewie <dirk.brandewie@gmail.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

1 files changed, 15 insertions, 2 deletions

diff --git a/drivers/i2c/busses/i2c-designware.c b/drivers/i2c/busses/i2c-designware.c
index 49386951f7fd..934dfe1e6ce9 100644
--- a/drivers/i2c/busses/i2c-designware.c
+++ b/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
@@ -216,6 +218,7 @@ 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;
@@ -223,11 +226,19 @@ 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);
 }
 
@@ -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;