linux-kernel - Re: [PATCH v1] PM / Domains: Add tracepoints

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Date:   Tue, 15 Oct 2019 14:37:42 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.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 <linux-pm@...r.kernel.org>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] PM / Domains: Add tracepoints

On Tue, 1 Oct 2019 at 18:35, Matthias Kaehlcke <mka@...omium.org> wrote:
>
> On Fri, Sep 27, 2019 at 04:42:39AM -0400, Steven Rostedt wrote:
> > On Thu, 26 Sep 2019 15:04:38 -0700
> > Matthias Kaehlcke <mka@...omium.org> wrote:
> >
> > > Define genpd_power_on/off and genpd_set_performance_state
> > > tracepoints and use them.
> >
> > I agree with Greg about adding a "why" you need this. But, in case
> > there's a good reason to have this, I have comments about the code
> > below.
>
> Thanks Greg and Steven for your comments.
>
> 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.

Apologize for the delay, no excuse!

I don't mind adding trace events, as long as it's for good reasons -
and to me, that seems a bit questionable here.

According to the above, I believe the information you need is already
available via genpd's debugfs interface, no?

[...]

Kind regards
Uffe