Hi,

quoted

+
+/**
+ * stm32f4_i2c_xfer() - Transfer combined I2C message
+ * @i2c_adap: Adapter pointer to the controller
+ * @msgs: Pointer to data to be written.
+ * @num: Number of messages to be executed
+ */
+static int stm32f4_i2c_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[],
+                           int num)
+{
+       struct stm32f4_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
+       int ret, i;
+
+       i2c_dev->busy = true;
+
+       ret = clk_prepare_enable(i2c_dev->clk);
+       if (ret) {
+               dev_err(i2c_dev->dev, "Failed to prepare_enable clock\n");
+               return ret;
+       }
+
+       stm32f4_i2c_hw_config(i2c_dev);

Maybe you could call this only at probe and resume time?
You would save some register accesses.

Some clarification about this point.
We need to call stm32f4_i2c_hw_config before each I2C transfer as at
the end of I2C communication the peripheral is automatically disabled
and configuration registers are reset.


BR,
Cedric