[PATCH] i2c: designware: Add support for 16bit register access

[Stefan Roese <sr-ynQEQJNshbs@public.gmane.org>]

The STM SPEAr platform can only access the i2c controller register
via 16bit read/write functions. This patch adds support to
automatically detect this 16bit access mode.

Signed-off-by: Stefan Roese <sr-ynQEQJNshbs@public.gmane.org>
---
 drivers/i2c/busses/i2c-designware-core.c |   22 ++++++++++++++++++++--
 drivers/i2c/busses/i2c-designware-core.h |    1 +
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index df87992..d1facbc 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -164,7 +164,14 @@ static char *abort_sources[] = {
 
 u32 dw_readl(struct dw_i2c_dev *dev, int offset)
 {
-	u32 value = readl(dev->base + offset);
+	u32 value;
+
+	if (dev->access_16bit) {
+		value = readw(dev->base + offset) |
+			(readw(dev->base + offset + 2) << 16);
+	} else {
+		value = readl(dev->base + offset);
+	}
 
 	if (dev->swab)
 		return swab32(value);
@@ -177,7 +184,12 @@ void dw_writel(struct dw_i2c_dev *dev, u32 b, int offset)
 	if (dev->swab)
 		b = swab32(b);
 
-	writel(b, dev->base + offset);
+	if (dev->access_16bit) {
+		writew((u16)b, dev->base + offset);
+		writew((u16)(b >> 16), dev->base + offset + 2);
+	} else {
+		writel(b, dev->base + offset);
+	}
 }
 
 static u32
@@ -258,6 +270,12 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
 		reg = DW_IC_COMP_TYPE_VALUE;
 	}
 
+	/* Configure register access mode 16bit */
+	if (reg == (DW_IC_COMP_TYPE_VALUE & 0x0000ffff)) {
+		dev->access_16bit = 1;
+		reg = DW_IC_COMP_TYPE_VALUE;
+	}
+
 	if (reg != DW_IC_COMP_TYPE_VALUE) {
 		dev_err(dev->dev, "Unknown Synopsys component type: "
 			"0x%08x\n", reg);
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index 02d1a2d..f5af101 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -83,6 +83,7 @@ struct dw_i2c_dev {
 	u32			abort_source;
 	int			irq;
 	int			swab;
+	int			access_16bit;
 	struct i2c_adapter	adapter;
 	u32			functionality;
 	u32			master_cfg;
-- 
1.7.9.2