Re: [PATCH 3/4] clock: Remove clock_get_ns()

[Luc Michel]

On 12/8/20 7:15 PM, Peter Maydell wrote:
> Remove the now-unused clock_get_ns() API and the CLOCK_PERIOD_TO_NS()
> macro that only it was using.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Luc Michel <luc@lmichel.fr>

> ---
>   docs/devel/clocks.rst | 17 +++++++++++++----
>   include/hw/clock.h    |  6 ------
>   2 files changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/docs/devel/clocks.rst b/docs/devel/clocks.rst
> index aebeedbb95e..9a93d1361b4 100644
> --- a/docs/devel/clocks.rst
> +++ b/docs/devel/clocks.rst
> @@ -238,8 +238,17 @@ object during device instance init. For example:
>   Fetching clock frequency/period
>   -------------------------------
>   
> -To get the current state of a clock, use the functions ``clock_get()``,
> -``clock_get_ns()`` or ``clock_get_hz()``.
> +To get the current state of a clock, use the functions ``clock_get()``
> +or ``clock_get_hz()``.
> +
> +``clock_get()`` returns the period of the clock in its fully precise
> +internal representation, as an unsigned 64-bit integer in units of
> +2^-32 nanoseconds. (For many purposes ``clock_ticks_to_ns()`` will
> +be more convenient; see the section below on expiry deadlines.)
> +
> +``clock_get_hz()`` returns the frequency of the clock, rounded to the
> +next lowest integer. This implies some inaccuracy due to the rounding,
> +so be cautious about using it in calculations.
>   
>   It is also possible to register a callback on clock frequency changes.
>   Here is an example:
> @@ -254,8 +263,8 @@ Here is an example:
>            */
>   
>           /* do something with the new period */
> -        fprintf(stdout, "device new period is %" PRIu64 "ns\n",
> -                        clock_get_ns(dev->my_clk_input));
> +        fprintf(stdout, "device new period is %" PRIu64 "* 2^-32 ns\n",
> +                        clock_get(dev->my_clk_input));
>       }
>   
>   Calculating expiry deadlines
> diff --git a/include/hw/clock.h b/include/hw/clock.h
> index a9425d9fb14..9c0b1eb4c3f 100644
> --- a/include/hw/clock.h
> +++ b/include/hw/clock.h
> @@ -39,7 +39,6 @@ typedef void ClockCallback(void *opaque);
>    * macro helpers to convert to hertz / nanosecond
>    */
>   #define CLOCK_PERIOD_FROM_NS(ns) ((ns) * (CLOCK_PERIOD_1SEC / 1000000000llu))
> -#define CLOCK_PERIOD_TO_NS(per) ((per) / (CLOCK_PERIOD_1SEC / 1000000000llu))
>   #define CLOCK_PERIOD_FROM_HZ(hz) (((hz) != 0) ? CLOCK_PERIOD_1SEC / (hz) : 0u)
>   #define CLOCK_PERIOD_TO_HZ(per) (((per) != 0) ? CLOCK_PERIOD_1SEC / (per) : 
> 0u)
>   
> @@ -214,11 +213,6 @@ static inline unsigned clock_get_hz(Clock *clk)
>       return CLOCK_PERIOD_TO_HZ(clock_get(clk));
>   }
>   
> -static inline unsigned clock_get_ns(Clock *clk)
> -{
> -    return CLOCK_PERIOD_TO_NS(clock_get(clk));
> -}
> -
>   /**
>    * clock_ticks_to_ns:
>    * @clk: the clock to query