[RFC] serial: mxc: get the clock frequency from the used clock for the device

[Michael Walle]

>> +		struct clk clk;
>> +		if(!clk_get_by_name(dev, "ipg", &clk))
>> +			rate = clk_get_rate(&clk);
>> +	}
>> +
>> +	/* as fallback we try to get the clk rate that way */
>> +	if (rate == 0)
> 
> !rate || IS_ERR_VALUE(rate)

This looked so weird I had to actually look at clk_get_rate()
in u-boot.

/**
  * clk_get_rate() - Get current clock rate.
  * @clk:	A clock struct that was previously successfully requested by
  *		clk_request/get_by_*().
  *
  * Return: clock rate in Hz on success, 0 for invalid clock, or -ve 
error code
  *	   for other errors.
  */
ulong clk_get_rate(struct clk *clk);

How can an ulong return a negative error value? What if the clock speed
happens to be the same as -errno?

-michael