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Message-ID: <20191001140846.65d7866c@gandalf.local.home>
Date: Tue, 1 Oct 2019 14:08:46 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Matthias Kaehlcke <mka@...omium.org>
Cc: "Rafael J . Wysocki" <rjw@...ysocki.net>,
Kevin Hilman <khilman@...nel.org>,
Ulf Hansson <ulf.hansson@...aro.org>,
Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Ingo Molnar <mingo@...hat.com>,
Douglas Anderson <dianders@...omium.org>,
linux-pm@...r.kernel.org, Amit Kucheria <amit.kucheria@...aro.org>,
linux-kernel@...r.kernel.org,
Ravi Chandra Sadineni <ravisadineni@...omium.org>
Subject: Re: [PATCH v1] PM / Domains: Add tracepoints
On Tue, 1 Oct 2019 10:42:35 -0700
Matthias Kaehlcke <mka@...omium.org> wrote:
> On Tue, Oct 01, 2019 at 01:03:43PM -0400, Steven Rostedt wrote:
> > On Tue, 1 Oct 2019 09:35:42 -0700
> > Matthias Kaehlcke <mka@...omium.org> wrote:
> >
> > > How about this instead:
> > >
> > > Add tracepoints for genpd_power_on, genpd_power_off and
> > > genpd_set_performance_state. The tracepoints can help with
> > > understanding power domain behavior of a given device, which
> > > may be particularly interesting for battery powered devices
> > > and suspend/resume.
> >
> > Do you have a use case example to present?
>
> TBH I'm not looking into a specific use case right now. While
> peeking around in /sys/kernel/debug/tracing/events to learn more
> about existing tracepoints that might be relevant for my work
> I noticed the absence of genpd ones and it seemed a good idea to
> add them preemptively. Conceptually they seem similar to the
> existing regulator_enable/disable and cpu_idle tracepoints.
>
> As an abstract use case I could see power analysis on battery
> powered devices during suspend. genpd_power_on/off allow to see
> which power domains remain on during suspend, and might give
> insights for possible power saving options. Examples could be that
> a power domain stays unexpectedly on due to a misconfiguration, or
> two power domains remain on when it could be only one if you just
> moved that one pin/port over to the other domain in the next
> hardware revision.
If the power management maintainers have no issues with adding these,
then neither do I ;-) It would be them who would pull them in anyway.
-- Steve
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