i2c: designware: Add support for changing the bus rate based on DT info

The Designware I2C driver does not currently support changing the bus
speed even if the hardware is capable of switching to a slower frequency.
Add support for passing the clock frequency info in the device tree.
Only standard (100kHz) or fast (400kHz) speeds are supported.

Signed-off-by: Andrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 9c78026..bcec19f 100644 (file)
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -122,6 +122,7 @@ static int dw_i2c_probe(struct platform_device *pdev)
        struct i2c_adapter *adap;
        struct resource *mem;
        int irq, r;
+       u32 bus_rate = DW_IC_CON_SPEED_STD;
 
        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
@@ -166,6 +167,22 @@ 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);
+
+               r = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
+                                               &bus_rate);
+               if (r)
+                       bus_rate = 400000; /* default clock rate */
+               switch (bus_rate) {
+               case 400000:
+                       bus_rate = DW_IC_CON_SPEED_FAST;
+                       break;
+               case 100000:
+                       bus_rate = DW_IC_CON_SPEED_STD;
+                       break;
+               default:
+                       dev_err(&pdev->dev, "Invalid bus speed (not 100kHz or 400kHz)\n");
+                       return -EINVAL;
+               }
        }
 
        dev->functionality =
@@ -176,7 +193,7 @@ 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 | bus_rate;
 
        /* Try first if we can configure the device from ACPI */
        r = dw_i2c_acpi_configure(pdev);