Re: [PATCH v1] PM / Domains: Add tracepoints

[Matthias Kaehlcke]

On Tue, Oct 01, 2019 at 02:08:46PM -0400, Steven Rostedt wrote:
> On Tue, 1 Oct 2019 10:42:35 -0700
> Matthias Kaehlcke <mka@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> 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.

Ok, I'll send a new version with the changes you suggested and some more
info in the commit message, unless PM maintainers raise concerns before
that.