Let clock_set_mul_div() return a boolean value whether the
clock has been updated or not, similarly to clock_set().

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/clock.h | 4 +++-
 hw/core/clock.c    | 8 +++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

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

On 16:58 Fri 22 Mar     , Philippe Mathieu-Daudé wrote:
> Let clock_set_mul_div() return a boolean value whether the
> clock has been updated or not, similarly to clock_set().
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

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

> ---
>  include/hw/clock.h | 4 +++-
>  hw/core/clock.c    | 8 +++++++-
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> 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
> 

On 09:40 Mon 25 Mar     , Luc Michel wrote:
> On 16:58 Fri 22 Mar     , Philippe Mathieu-Daudé wrote:
> > Let clock_set_mul_div() return a boolean value whether the
> > clock has been updated or not, similarly to clock_set().
> > 
> > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> 
> Acked-by: Luc Michel <luc@lmichel.fr>

Sorry, I forgot, as Peter suggested, can you add a word in the doc
about this?

Something in the vein of:

+ Similary to ``clock_set()``, ``clock_set_mul_div()`` returns ``true`` if
+ the clock state was modified, that it, 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.

Thanks!

-- 
Luc

> 
> > ---
> >  include/hw/clock.h | 4 +++-
> >  hw/core/clock.c    | 8 +++++++-
> >  2 files changed, 10 insertions(+), 2 deletions(-)
> > 
> > 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
> > 
> 

-- 

On Fri, 22 Mar 2024 at 15:58, 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().
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  include/hw/clock.h | 4 +++-
>  hw/core/clock.c    | 8 +++++++-
>  2 files changed, 10 insertions(+), 2 deletions(-)


I guess this makes sense, especially since you often would like to know
this to decide whether to call clock_propagate().

We should also update the docs/devel/clocks.rst to mention this.

thanks
-- PMM