[PATCH-for-9.0 0/2] hw/clock: Propagate clock changes when STM32L4X5 MUX is updated

[PATCH-for-9.0 0/2] hw/clock: Propagate clock changes when STM32L4X5 MUX is updated

[Philippe Mathieu-Daudé]

Per https://www.qemu.org/docs/master/devel/clocks.html#clock-multiplier-and-divider-settings:

  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.

Fix what we forgot to do that in recent commit ec7d83acbd
("hw/misc/stm32l4x5_rcc: Add an internal clock multiplexer object")

Arnaud Minier (1):
  hw/misc/stm32l4x5_rcc: Propagate period when enabling a clock

Philippe Mathieu-Daudé (1):
  hw/clock: Let clock_set_mul_div() return boolean value

 include/hw/clock.h      | 4 +++-
 hw/core/clock.c         | 8 +++++++-
 hw/misc/stm32l4x5_rcc.c | 5 ++++-
 3 files changed, 14 insertions(+), 3 deletions(-)

-- 
2.41.0

[PATCH-for-9.0 1/2] hw/clock: Let clock_set_mul_div() return boolean value

[Philippe Mathieu-Daudé]

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

[PATCH-for-9.0 2/2] hw/misc/stm32l4x5_rcc: Propagate period when enabling a clock

[Philippe Mathieu-Daudé]

From: Arnaud Minier <arnaud.minier@telecom-paris.fr>

The "clock_set_mul_div" function doesn't propagate the clock period
to the children if it is changed (e.g. by enabling/disabling a clock
multiplexer).
This was overlooked during the implementation due to late changes.

This commit propagates the change if the multiplier or divider changes.

Fixes: ec7d83acbd ("hw/misc/stm32l4x5_rcc: Add an internal clock multiplexer object")
Signed-off-by: Arnaud Minier <arnaud.minier@telecom-paris.fr>
Signed-off-by: Inès Varhol <ines.varhol@telecom-paris.fr>
Message-ID: <20240317103918.44375-2-arnaud.minier@telecom-paris.fr>
[PMD: Check clock_set_mul_div() return value]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/misc/stm32l4x5_rcc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/misc/stm32l4x5_rcc.c b/hw/misc/stm32l4x5_rcc.c
index bc2d63528b..7ad628b296 100644
--- a/hw/misc/stm32l4x5_rcc.c
+++ b/hw/misc/stm32l4x5_rcc.c
@@ -59,7 +59,10 @@ static void clock_mux_update(RccClockMuxState *mux, bool bypass_source)
         freq_multiplier = mux->divider;
     }
 
-    clock_set_mul_div(mux->out, freq_multiplier, mux->multiplier);
+    if (clock_set_mul_div(mux->out, freq_multiplier, mux->multiplier)) {
+        clock_propagate(mux->out);
+    }
+
     clock_update(mux->out, clock_get(current_source));
 
     src_freq = clock_get_hz(current_source);
-- 
2.41.0

Re: [PATCH-for-9.0 2/2] hw/misc/stm32l4x5_rcc: Propagate period when enabling a clock

[Peter Maydell]

On Fri, 22 Mar 2024 at 15:59, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>
> From: Arnaud Minier <arnaud.minier@telecom-paris.fr>
>
> The "clock_set_mul_div" function doesn't propagate the clock period
> to the children if it is changed (e.g. by enabling/disabling a clock
> multiplexer).
> This was overlooked during the implementation due to late changes.
>
> This commit propagates the change if the multiplier or divider changes.
>
> Fixes: ec7d83acbd ("hw/misc/stm32l4x5_rcc: Add an internal clock multiplexer object")
> Signed-off-by: Arnaud Minier <arnaud.minier@telecom-paris.fr>
> Signed-off-by: Inès Varhol <ines.varhol@telecom-paris.fr>
> Message-ID: <20240317103918.44375-2-arnaud.minier@telecom-paris.fr>
> [PMD: Check clock_set_mul_div() return value]
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  hw/misc/stm32l4x5_rcc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/hw/misc/stm32l4x5_rcc.c b/hw/misc/stm32l4x5_rcc.c
> index bc2d63528b..7ad628b296 100644
> --- a/hw/misc/stm32l4x5_rcc.c
> +++ b/hw/misc/stm32l4x5_rcc.c
> @@ -59,7 +59,10 @@ static void clock_mux_update(RccClockMuxState *mux, bool bypass_source)
>          freq_multiplier = mux->divider;
>      }
>
> -    clock_set_mul_div(mux->out, freq_multiplier, mux->multiplier);
> +    if (clock_set_mul_div(mux->out, freq_multiplier, mux->multiplier)) {
> +        clock_propagate(mux->out);
> +    }
> +
>      clock_update(mux->out, clock_get(current_source));

clock_update() also calls clock_propagate(), so this doesn't
seem entirely right: shouldn't we figure out whether we need to
do a clock_propagate() and do it once? (Maybe what seems odd to me
is that clock_set() does clock_propagate() for you but
clock_set_mul_div() does not...)

(Also I think we should have the information we need now to be able
to do the "reduce log spam" in the comment -- if neither
clock_set_mul_div() nor clock_update() needed to do anything
then we didn't actually change the config.)

-- PMM

Re: [PATCH-for-9.0 1/2] hw/clock: Let clock_set_mul_div() return boolean value

[Peter Maydell]

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

Re: [PATCH-for-9.0 1/2] hw/clock: Let clock_set_mul_div() return boolean value

[Luc Michel]

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
> 

Re: [PATCH-for-9.0 2/2] hw/misc/stm32l4x5_rcc: Propagate period when enabling a clock

[Luc Michel]

On 16:39 Fri 22 Mar     , Peter Maydell wrote:
> On Fri, 22 Mar 2024 at 15:59, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
> >
> > From: Arnaud Minier <arnaud.minier@telecom-paris.fr>
> >
> > The "clock_set_mul_div" function doesn't propagate the clock period
> > to the children if it is changed (e.g. by enabling/disabling a clock
> > multiplexer).
> > This was overlooked during the implementation due to late changes.
> >
> > This commit propagates the change if the multiplier or divider changes.
> >
> > Fixes: ec7d83acbd ("hw/misc/stm32l4x5_rcc: Add an internal clock multiplexer object")
> > Signed-off-by: Arnaud Minier <arnaud.minier@telecom-paris.fr>
> > Signed-off-by: Inès Varhol <ines.varhol@telecom-paris.fr>
> > Message-ID: <20240317103918.44375-2-arnaud.minier@telecom-paris.fr>
> > [PMD: Check clock_set_mul_div() return value]
> > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > ---
> >  hw/misc/stm32l4x5_rcc.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/misc/stm32l4x5_rcc.c b/hw/misc/stm32l4x5_rcc.c
> > index bc2d63528b..7ad628b296 100644
> > --- a/hw/misc/stm32l4x5_rcc.c
> > +++ b/hw/misc/stm32l4x5_rcc.c
> > @@ -59,7 +59,10 @@ static void clock_mux_update(RccClockMuxState *mux, bool bypass_source)
> >          freq_multiplier = mux->divider;
> >      }
> >
> > -    clock_set_mul_div(mux->out, freq_multiplier, mux->multiplier);
> > +    if (clock_set_mul_div(mux->out, freq_multiplier, mux->multiplier)) {
> > +        clock_propagate(mux->out);
> > +    }
> > +
> >      clock_update(mux->out, clock_get(current_source));
> 
> clock_update() also calls clock_propagate(), so this doesn't
> seem entirely right: shouldn't we figure out whether we need to
> do a clock_propagate() and do it once? (Maybe what seems odd to me
> is that clock_set() does clock_propagate() for you but
> clock_set_mul_div() does not...)
clock_set() does not call clock_propagate(). clock_update() is a
clock_set() followed by a clock_propagate() if the period changed.

I think this is where the problem comes from here. clock_update() call
won't call clock_propagate() if the clock period does not change.

I think you'll want something like:
    bool changed;

    changed = clock_set_mul_div(mux->out, freq_multiplier, mux->multiplexer);
    changed ||= clock_set(clock_get(current_source));

    if (changed) {
        clock_propagate(mux->out);
    }
 
Thanks,

-- 
Luc

> 
> (Also I think we should have the information we need now to be able
> to do the "reduce log spam" in the comment -- if neither
> clock_set_mul_div() nor clock_update() needed to do anything
> then we didn't actually change the config.)
> 
> -- PMM

-- 

Re: [PATCH-for-9.0 1/2] hw/clock: Let clock_set_mul_div() return boolean value

[Luc Michel]

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
> > 
> 

--