Re: [PATCH-for-9.0 v3 1/3] hw/clock: Let clock_set_mul_div() return a boolean value

[Alistair Francis <alistair23@gmail.com>]

On Tue, Mar 26, 2024 at 1:29 AM Philippe Mathieu-Daudé
<philmd@linaro.org> wrote:
>
> Let clock_set_mul_div() return a boolean value whether the
> clock has been updated or not, similarly to clock_set().
>
> Return early when clock_set_mul_div() is called with
> same mul/div values the clock has.
>
> Acked-by: Luc Michel <luc@lmichel.fr>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  docs/devel/clocks.rst | 4 ++++
>  include/hw/clock.h    | 4 +++-
>  hw/core/clock.c       | 8 +++++++-
>  3 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/docs/devel/clocks.rst b/docs/devel/clocks.rst
> index c4d14bde04..b2d1148cdb 100644
> --- a/docs/devel/clocks.rst
> +++ b/docs/devel/clocks.rst
> @@ -279,6 +279,10 @@ You can change the multiplier and divider of a clock at runtime,
>  so you can use this to model clock controller devices which
>  have guest-programmable frequency multipliers or dividers.
>
> +Similary to ``clock_set()``, ``clock_set_mul_div()`` returns ``true`` if
> +the clock state was modified; that is, if the multiplier or the diviser
> +or both were changed by the call.
> +
>  Note that ``clock_set_mul_div()`` does not automatically call
>  ``clock_propagate()``. If you make a runtime change to the
>  multiplier or divider you must call clock_propagate() yourself.
> diff --git a/include/hw/clock.h b/include/hw/clock.h
> index bb12117f67..eb58599131 100644
> --- a/include/hw/clock.h
> +++ b/include/hw/clock.h
> @@ -357,6 +357,8 @@ char *clock_display_freq(Clock *clk);
>   * @multiplier: multiplier value
>   * @divider: divider value
>   *
> + * @return: true if the clock is changed.
> + *
>   * By default, a Clock's children will all run with the same period
>   * as their parent. This function allows you to adjust the multiplier
>   * and divider used to derive the child clock frequency.
> @@ -374,6 +376,6 @@ char *clock_display_freq(Clock *clk);
>   * Note that this function does not call clock_propagate(); the
>   * caller should do that if necessary.
>   */
> -void clock_set_mul_div(Clock *clk, uint32_t multiplier, uint32_t divider);
> +bool clock_set_mul_div(Clock *clk, uint32_t multiplier, uint32_t divider);
>
>  #endif /* QEMU_HW_CLOCK_H */
> diff --git a/hw/core/clock.c b/hw/core/clock.c
> index d82e44cd1a..a19c7db7df 100644
> --- a/hw/core/clock.c
> +++ b/hw/core/clock.c
> @@ -143,14 +143,20 @@ char *clock_display_freq(Clock *clk)
>      return freq_to_str(clock_get_hz(clk));
>  }
>
> -void clock_set_mul_div(Clock *clk, uint32_t multiplier, uint32_t divider)
> +bool clock_set_mul_div(Clock *clk, uint32_t multiplier, uint32_t divider)
>  {
>      assert(divider != 0);
>
> +    if (clk->multiplier == multiplier && clk->divider == divider) {
> +        return false;
> +    }
> +
>      trace_clock_set_mul_div(CLOCK_PATH(clk), clk->multiplier, multiplier,
>                              clk->divider, divider);
>      clk->multiplier = multiplier;
>      clk->divider = divider;
> +
> +    return true;
>  }
>
>  static void clock_initfn(Object *obj)
> --
> 2.41.0
>
>