linux-kernel - Re: [PATCH v2] PM: runtime: add tracepoint for runtime

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Date: Thu, 22 Feb 2024 20:28:59 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Vilas Bhat <vilasbhat@...gle.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Saravana Kannan <saravanak@...gle.com>, kernel-team@...roid.com, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PM: runtime: add tracepoint for runtime_status changes

On Wed, Feb 21, 2024 at 8:49 PM Vilas Bhat <vilasbhat@...gle.com> wrote:
>
> Existing runtime PM ftrace events (`rpm_suspend`, `rpm_resume`,
> `rpm_return_int`) offer limited visibility into the exact timing of device
> runtime power state transitions, particularly when asynchronous operations
> are involved. When the `rpm_suspend` or `rpm_resume` functions are invoked
> with the `RPM_ASYNC` flag, a return value of 0 i.e., success merely
> indicates that the device power state request has been queued, not that
> the device has yet transitioned.
>
> A new ftrace event, `rpm_status`, is introduced. This event directly logs
> the `power.runtime_status` value of a device whenever it changes providing
> granular tracking of runtime power state transitions regardless of
> synchronous or asynchronous `rpm_suspend` / `rpm_resume` usage.
>
> Signed-off-by: Vilas Bhat <vilasbhat@...gle.com>
> ---
> V1 -> V2: Modified enum value definition as per reviewer comments.
> ---
>  drivers/base/power/runtime.c |  1 +
>  include/trace/events/rpm.h   | 42 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 43 insertions(+)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index 05793c9fbb84..d10354847878 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -94,6 +94,7 @@ static void update_pm_runtime_accounting(struct device *dev)
>  static void __update_runtime_status(struct device *dev, enum rpm_status status)
>  {
>         update_pm_runtime_accounting(dev);
> +       trace_rpm_status(dev, status);
>         dev->power.runtime_status = status;
>  }
>
> diff --git a/include/trace/events/rpm.h b/include/trace/events/rpm.h
> index 3c716214dab1..bd120e23ce12 100644
> --- a/include/trace/events/rpm.h
> +++ b/include/trace/events/rpm.h
> @@ -101,6 +101,48 @@ TRACE_EVENT(rpm_return_int,
>                 __entry->ret)
>  );
>
> +#define RPM_STATUS_STRINGS \
> +       EM(RPM_INVALID, "RPM_INVALID") \
> +       EM(RPM_ACTIVE, "RPM_ACTIVE") \
> +       EM(RPM_RESUMING, "RPM_RESUMING") \
> +       EM(RPM_SUSPENDED, "RPM_SUSPENDED") \
> +       EMe(RPM_SUSPENDING, "RPM_SUSPENDING")
> +
> +/* Enums require being exported to userspace, for user tool parsing. */
> +#undef EM
> +#undef EMe
> +#define EM(a, b)       TRACE_DEFINE_ENUM(a);
> +#define EMe(a, b)      TRACE_DEFINE_ENUM(a);
> +
> +RPM_STATUS_STRINGS
> +
> +/*
> + * Now redefine the EM() and EMe() macros to map the enums to the strings that
> + * will be printed in the output.
> + */
> +#undef EM
> +#undef EMe
> +#define EM(a, b)       { a, b },
> +#define EMe(a, b)      { a, b }
> +
> +TRACE_EVENT(rpm_status,
> +       TP_PROTO(struct device *dev, enum rpm_status status),
> +       TP_ARGS(dev, status),
> +
> +       TP_STRUCT__entry(
> +               __string(name,  dev_name(dev))
> +               __field(int,    status)
> +       ),
> +
> +       TP_fast_assign(
> +               __assign_str(name, dev_name(dev));
> +               __entry->status = status;
> +       ),
> +
> +       TP_printk("%s status=%s", __get_str(name),
> +               __print_symbolic(__entry->status, RPM_STATUS_STRINGS))
> +);
> +
>  #endif /* _TRACE_RUNTIME_POWER_H */
>
>  /* This part must be outside protection */
> --

Applied as 6.9 material, thanks!