Re: [PATCH v3 02/15] hw/core/clock: trace clock values in Hz instead of ns - Philippe Mathieu-Daudé

From: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
To: Luc Michel <luc@lmichel.fr>, qemu-devel@nongnu.org
Cc: Damien Hedde <damien.hedde@greensocs.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	Havard Skinnemoen <hskinnemoen@google.com>,
	Andrew Baumann <Andrew.Baumann@microsoft.com>,
	Paul Zimmerman <pauldzim@gmail.com>,
	Niek Linnenbank <nieklinnenbank@gmail.com>,
	qemu-arm@nongnu.org
Subject: Re: [PATCH v3 02/15] hw/core/clock: trace clock values in Hz instead of ns
Date: Sat, 10 Oct 2020 17:48:06 +0200	[thread overview]
Message-ID: <46c493aa-5aa8-a518-5a67-2d0e04523470@amsat.org> (raw)
In-Reply-To: <20201010135759.437903-3-luc@lmichel.fr>

On 10/10/20 3:57 PM, Luc Michel wrote:
> The nanosecond unit greatly limits the dynamic range we can display in
> clock value traces, for values in the order of 1GHz and more. The
> internal representation can go way beyond this value and it is quite
> common for today's clocks to be within those ranges.
> 
> For example, a frequency between 500MHz+ and 1GHz will be displayed as
> 1ns. Beyond 1GHz, it will show up as 0ns.
> 
> Replace nanosecond periods traces with frequencies in the Hz unit
> to have more dynamic range in the trace output.
> 
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Reviewed-by: Damien Hedde <damien.hedde@greensocs.com>
> Signed-off-by: Luc Michel <luc@lmichel.fr>
> ---
>   hw/core/clock.c      | 6 +++---
>   hw/core/trace-events | 4 ++--
>   2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/core/clock.c b/hw/core/clock.c
> index 7066282f7b..81184734e0 100644
> --- a/hw/core/clock.c
> +++ b/hw/core/clock.c
> @@ -37,12 +37,12 @@ void clock_clear_callback(Clock *clk)
>   bool clock_set(Clock *clk, uint64_t period)
>   {
>       if (clk->period == period) {
>           return false;
>       }
> -    trace_clock_set(CLOCK_PATH(clk), CLOCK_PERIOD_TO_NS(clk->period),
> -                    CLOCK_PERIOD_TO_NS(period));
> +    trace_clock_set(CLOCK_PATH(clk), CLOCK_PERIOD_TO_HZ(clk->period),
> +                    CLOCK_PERIOD_TO_HZ(period));
>       clk->period = period;
>   
>       return true;
>   }
>   
> @@ -52,11 +52,11 @@ static void clock_propagate_period(Clock *clk, bool call_callbacks)
>   
>       QLIST_FOREACH(child, &clk->children, sibling) {
>           if (child->period != clk->period) {
>               child->period = clk->period;
>               trace_clock_update(CLOCK_PATH(child), CLOCK_PATH(clk),
> -                               CLOCK_PERIOD_TO_NS(clk->period),
> +                               CLOCK_PERIOD_TO_HZ(clk->period),
>                                  call_callbacks);
>               if (call_callbacks && child->callback) {
>                   child->callback(child->callback_opaque);
>               }
>               clock_propagate_period(child, call_callbacks);
> diff --git a/hw/core/trace-events b/hw/core/trace-events
> index 1ac60ede6b..360ddeb2c8 100644
> --- a/hw/core/trace-events
> +++ b/hw/core/trace-events
> @@ -29,8 +29,8 @@ resettable_phase_exit_end(void *obj, const char *objtype, unsigned count) "obj=%
>   resettable_transitional_function(void *obj, const char *objtype) "obj=%p(%s)"
>   
>   # clock.c
>   clock_set_source(const char *clk, const char *src) "'%s', src='%s'"
>   clock_disconnect(const char *clk) "'%s'"
> -clock_set(const char *clk, uint64_t old, uint64_t new) "'%s', ns=%"PRIu64"->%"PRIu64
> +clock_set(const char *clk, uint64_t old, uint64_t new) "'%s', %"PRIu64"Hz->%"PRIu64"Hz"

I find it easier to read/follow as: "'%s', %"PRIu64" -> %"PRIu64" Hz",
you see the number directly, no need for the brain to extract the
trailing "Hz".

Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

>   clock_propagate(const char *clk) "'%s'"
> -clock_update(const char *clk, const char *src, uint64_t val, int cb) "'%s', src='%s', ns=%"PRIu64", cb=%d"
> +clock_update(const char *clk, const char *src, uint64_t hz, int cb) "'%s', src='%s', val=%"PRIu64"Hz cb=%d"
> 