i2c: meson: use i2c core for DT clock-frequency parsing

We don't have to parse the DT manually to retrieve the bus frequency
and we don't have to maintain an own default for the bus frequency.
Let the i2c core do this for us.
Signed-off-by: NHeiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: NJerome Brunet <jbrunet@baylibre.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-meson.txt

@@ -8,6 +8,8 @@ Required properties:
  - #address-cells: should be <1>
  - #size-cells: should be <0>
 
+For details regarding the following core I2C bindings see also i2c.txt.
+
 Optional properties:
 - clock-frequency: the desired I2C bus clock frequency in Hz; in
   absence of this property the default value is used (100 kHz).

drivers/i2c/busses/i2c-meson.c

@@ -38,7 +38,6 @@
 #define REG_CTRL_CLKDIV_MASK	((BIT(10) - 1) << REG_CTRL_CLKDIV_SHIFT)
 
 #define I2C_TIMEOUT_MS		500
-#define DEFAULT_FREQ		100000
 
 enum {
 	TOKEN_END = 0,
@@ -387,15 +386,14 @@ static int meson_i2c_probe(struct platform_device *pdev)
 	struct device_node *np = pdev->dev.of_node;
 	struct meson_i2c *i2c;
 	struct resource *mem;
-	u32 freq;
+	struct i2c_timings timings;
 	int irq, ret = 0;
 
 	i2c = devm_kzalloc(&pdev->dev, sizeof(struct meson_i2c), GFP_KERNEL);
 	if (!i2c)
 		return -ENOMEM;
 
-	if (of_property_read_u32(pdev->dev.of_node, "clock-frequency", &freq))
-		freq = DEFAULT_FREQ;
+	i2c_parse_fw_timings(&pdev->dev, &timings, true);
 
 	i2c->dev = &pdev->dev;
 	platform_set_drvdata(pdev, i2c);
@@ -452,7 +450,7 @@ static int meson_i2c_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	meson_i2c_set_clk_div(i2c, freq);
+	meson_i2c_set_clk_div(i2c, timings.bus_freq_hz);
 
 	return 0;
 }