On 3/17/22 10:47 AM, Michael Walle wrote:
+ 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?
It can't. Which is why we need IS_ERR_VALUE and not < 0.
What if the clock speed happens to be the same as -errno?
Due to physical constraints, this isn't an issue on 64 bit systems. And you could run into trouble if you have a 32-bit system with a 4GHz processor.
I don't think it's the best interface. In e.g. Linux clk_get_rate returns 0 on failure, which I think is reasonable. If you are interested, please send a patch series :)
--Sean