i2c: add generic routine to parse DT for timing information

Inspired from the i2c-rk3x driver (thanks guys!) but refactored and
extended. See built-in docs for further information.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 51028f3..bc2b19a 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -414,6 +414,22 @@
 };
 
 /**
+ * struct i2c_timings - I2C timing information
+ * @bus_freq_hz: the bus frequency in Hz
+ * @scl_rise_ns: time SCL signal takes to rise in ns; t(r) in the I2C specification
+ * @scl_fall_ns: time SCL signal takes to fall in ns; t(f) in the I2C specification
+ * @scl_int_delay_ns: time IP core additionally needs to setup SCL in ns
+ * @sda_fall_ns: time SDA signal takes to fall in ns; t(f) in the I2C specification
+ */
+struct i2c_timings {
+	u32 bus_freq_hz;
+	u32 scl_rise_ns;
+	u32 scl_fall_ns;
+	u32 scl_int_delay_ns;
+	u32 sda_fall_ns;
+};
+
+/**
  * struct i2c_bus_recovery_info - I2C bus recovery information
  * @recover_bus: Recover routine. Either pass driver's recover_bus() routine, or
  *	i2c_generic_scl_recovery() or i2c_generic_gpio_recovery().
@@ -604,6 +620,7 @@
 extern struct i2c_adapter *i2c_get_adapter(int nr);
 extern void i2c_put_adapter(struct i2c_adapter *adap);
 
+void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults);
 
 /* Return the functionality mask */
 static inline u32 i2c_get_functionality(struct i2c_adapter *adap)
@@ -660,6 +677,7 @@
 
 /* must call i2c_put_adapter() when done with returned i2c_adapter device */
 struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node);
+
 #else
 
 static inline struct i2c_client *of_find_i2c_device_by_node(struct device_node *node)