[PATCH] i2c: designware: deduce speed mode from device tree setting

[<atull@opensource.altera.com>]

From: Alan Tull <atull@opensource.altera.com>

Use the documented, but unimplemented "clock-frequency"
Device Tree setting as a guide on whether to set the speed
mode bits in DW_IC_CON to standard or fast i2c mode.

Previously, the driver was hardwired to fast mode.  Default
to fast mode if the "clock-frequency" property is not present
for backwards compatiblity.

Signed-off-by: Alan Tull <atull@opensource.altera.com>
---
 drivers/i2c/busses/i2c-designware-platdrv.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index bc87733..18cd3d9 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -122,7 +122,8 @@ static int dw_i2c_probe(struct platform_device *pdev)
 	struct dw_i2c_dev *dev;
 	struct i2c_adapter *adap;
 	struct resource *mem;
-	int irq, r;
+	int irq, r, ret, speed = DW_IC_CON_SPEED_FAST;
+	u32 bus_rate;
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0) {
@@ -167,6 +168,11 @@ static int dw_i2c_probe(struct platform_device *pdev)
 		of_property_read_u32(pdev->dev.of_node,
 				     "i2c-scl-falling-time-ns",
 				     &dev->scl_falling_time);
+
+		ret = of_property_read_u32(pdev->dev.of_node,
+					   "clock-frequency", &bus_rate);
+		if (!ret && (bus_rate <= 100000))
+			speed = DW_IC_CON_SPEED_STD;
 	}
 
 	dev->functionality =
@@ -177,7 +183,7 @@ static int dw_i2c_probe(struct platform_device *pdev)
 		I2C_FUNC_SMBUS_WORD_DATA |
 		I2C_FUNC_SMBUS_I2C_BLOCK;
 	dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
-		DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
+		DW_IC_CON_RESTART_EN | speed;
 
 	/* Try first if we can configure the device from ACPI */
 	r = dw_i2c_acpi_configure(pdev);
-- 
1.7.9.5