linux-kernel - Re: [PATCH] cpufreq: conservative: Do not use transition notifications

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Message-ID: <3863285.5KT0E88Y5I@vostro.rjw.lan>
Date:	Mon, 13 Jun 2016 22:57:35 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH] cpufreq: conservative: Do not use transition notifications

On Monday, June 13, 2016 08:58:34 PM Viresh Kumar wrote:
> On 13-06-16, 15:36, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Subject: [PATCH v2] cpufreq: conservative: Do not use transition notifications
> > 
> > The conservative governor registers a transition notifier so it
> > can update its internal requested_freq value if it falls out of the
> > policy->min...policy->max range, but requested_freq is not really
> > necessary.
> > 
> > That value is used to track the frequency requested by the governor
> > previously, but policy->cur can be used instead of it and then the
> > governor will not have to worry about updating the tracked value when
> > the current frequency changes independently (for example, as a result
> > of min or max changes).
> > 
> > Accodringly, drop requested_freq from struct cs_policy_dbs_info
> > and modify cs_dbs_timer() to use policy->cur instead of it.
> > While at it, notice that __cpufreq_driver_target() clamps its
> > target_freq argument between policy->min and policy->max, so
> > the callers of it don't have to do that and make additional
> > changes in cs_dbs_timer() in accordance with that.
> > 
> > After these changes the transition notifier used by the conservative
> > governor is not necessary any more, so drop it, which also makes it
> > possible to drop the struct cs_governor definition and simplify the
> > code accordingly.
> > 
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/cpufreq/cpufreq_conservative.c |  103 ++++++---------------------------
> >  1 file changed, 21 insertions(+), 82 deletions(-)
> > 
> 
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

Thanks!

> > -static struct cs_governor cs_gov = {
> > -	.dbs_gov = {
> > -		.gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"),
> > -		.kobj_type = { .default_attrs = cs_attributes },
> > -		.gov_dbs_timer = cs_dbs_timer,
> > -		.alloc = cs_alloc,
> > -		.free = cs_free,
> > -		.init = cs_init,
> > -		.exit = cs_exit,
> > -		.start = cs_start,
> > -	},
> > +static struct dbs_governor cs_governor = {
> > +	.gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"),
> > +	.kobj_type = { .default_attrs = cs_attributes },
> > +	.gov_dbs_timer = cs_dbs_timer,
> > +	.alloc = cs_alloc,
> > +	.free = cs_free,
> > +	.init = cs_init,
> > +	.exit = cs_exit,
> > +	.start = cs_start,
> >  };
> 
> Though, I am not sure why this change was required :)

This is because struct cs_governor is not necessary any more, since its only
member, usage_count, was only needed because of the notifier.  So dbs_governor
can be used directly here now.

Thanks,
Rafael