From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Date: Thu, 21 Jul 2016 22:52:43 +0200 Message-ID: <1628802.LW0F6bbOgI@vostro.rjw.lan> References: <1468441527-23534-1-git-send-email-smuckle@linaro.org> <2012245.HQXNKhffmu@vostro.rjw.lan> <20160721203041.GH3122@ubuntu> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7Bit Return-path: Received: from cloudserver094114.home.net.pl ([79.96.170.134]:57653 "HELO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753968AbcGUUrr (ORCPT ); Thu, 21 Jul 2016 16:47:47 -0400 In-Reply-To: <20160721203041.GH3122@ubuntu> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Viresh Kumar Cc: Steve Muckle , Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Vincent Guittot , Morten Rasmussen , Dietmar Eggemann , Juri Lelli , Patrick Bellasi , Steve Muckle On Thursday, July 21, 2016 01:30:41 PM Viresh Kumar wrote: > On 21-07-16, 22:31, Rafael J. Wysocki wrote: > > On Thursday, July 21, 2016 12:59:26 PM Viresh Kumar wrote: > > > On 13-07-16, 13:25, Steve Muckle wrote: > > > > Cpufreq governors may need to know what a particular target frequency > > > > maps to in the driver without necessarily wanting to set the frequency. > > > > Support this operation via a new cpufreq API, > > > > cpufreq_driver_resolve_freq(). This API returns the lowest driver > > > > frequency equal or greater than the target frequency > > > > (CPUFREQ_RELATION_L), subject to any policy (min/max) or driver > > > > limitations. The mapping is also cached in the policy so that a > > > > subsequent fast_switch operation can avoid repeating the same lookup. > > > > > > > > The API will call a new cpufreq driver callback, resolve_freq(), if it > > > > has been registered by the driver. Otherwise the frequency is resolved > > > > via cpufreq_frequency_table_target(). Rather than require ->target() > > > > style drivers to provide a resolve_freq() callback it is left to the > > > > caller to ensure that the driver implements this callback if necessary > > > > to use cpufreq_driver_resolve_freq(). > > > > > > > > Suggested-by: Rafael J. Wysocki > > > > Signed-off-by: Steve Muckle > > > > --- > > > > drivers/cpufreq/cpufreq.c | 25 +++++++++++++++++++++++++ > > > > include/linux/cpufreq.h | 16 ++++++++++++++++ > > > > 2 files changed, 41 insertions(+) > > > > > > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > > > > index 118b4f30a406..b696baeb249d 100644 > > > > --- a/drivers/cpufreq/cpufreq.c > > > > +++ b/drivers/cpufreq/cpufreq.c > > > > @@ -492,6 +492,29 @@ void cpufreq_disable_fast_switch(struct cpufreq_policy *policy) > > > > } > > > > EXPORT_SYMBOL_GPL(cpufreq_disable_fast_switch); > > > > > > > > +/** > > > > + * cpufreq_driver_resolve_freq - Map a target frequency to a driver-supported > > > > + * one. > > > > + * @target_freq: target frequency to resolve. > > > > + * > > > > + * The target to driver frequency mapping is cached in the policy. > > > > + * > > > > + * Return: Lowest driver-supported frequency greater than or equal to the > > > > + * given target_freq, subject to policy (min/max) and driver limitations. > > > > + */ > > > > +unsigned int cpufreq_driver_resolve_freq(struct cpufreq_policy *policy, > > > > + unsigned int target_freq) > > > > +{ > > > > + target_freq = clamp_val(target_freq, policy->min, policy->max); > > > > + policy->cached_target_freq = target_freq; > > > > + if (cpufreq_driver->resolve_freq) > > > > + return cpufreq_driver->resolve_freq(policy, target_freq); > > > > > > Any reason why we still have this call around ? I thought the whole > > > attempt I made was to get rid of this :) > > > > > > The core can do this pretty much now by itself, why do we still want > > > this call? > > > > In case some drivers that don't use frequency tables want to implemet > > fast switching, for example. > > Okay, but in that case shouldn't we do something like this: That'd be fine by me. Please send a patch on top of the Steve's series and I can apply it too (unless Steve sees some major problems in it, which seems unlikely to me). > unsigned int cpufreq_driver_resolve_freq(struct cpufreq_policy *policy, > unsigned int target_freq) > { > target_freq = clamp_val(target_freq, policy->min, policy->max); > policy->cached_target_freq = target_freq; > > if (cpufreq_driver->target_index) { > policy->cached_resolved_idx = > cpufreq_frequency_table_target(policy, target_freq, > CPUFREQ_RELATION_L); > return policy->freq_table[policy->cached_resolved_idx].frequency; > } > > if (cpufreq_driver->resolve_freq) > return cpufreq_driver->resolve_freq(policy, target_freq); > } > > ?? Thanks, Rafael