From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linda Knippers Subject: Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency" Date: Fri, 22 Jul 2016 15:25:43 -0400 Message-ID: References: <20160722151411.GB11711@suselix.suse.de> <20160722153656.GR3122@ubuntu> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160722153656.GR3122@ubuntu> Sender: linux-kernel-owner@vger.kernel.org To: Viresh Kumar , "Rafael J. Wysocki" , Andreas Herrmann Cc: Jacob Tanenbaum , stable@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-pm@vger.kernel.org On 7/22/2016 11:36 AM, Viresh Kumar wrote: > On 22-07-16, 17:14, Andreas Herrmann wrote: >> diff --git a/drivers/cpufreq/pcc-cpufreq.c b/drivers/cpufreq/pcc-cpufreq.c >> index a7ecb9a..3f0ce2a 100644 >> --- a/drivers/cpufreq/pcc-cpufreq.c >> +++ b/drivers/cpufreq/pcc-cpufreq.c >> @@ -555,8 +555,6 @@ static int pcc_cpufreq_cpu_init(struct cpufreq_policy *policy) >> policy->min = policy->cpuinfo.min_freq = >> ioread32(&pcch_hdr->minimum_frequency) * 1000; >> >> - policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL; >> - >> pr_debug("init: policy->max is %d, policy->min is %d\n", >> policy->max, policy->min); >> out: > > Hi Rafael, > > I am very confused on this, can you help me understand ? > > - CPUFREQ_ETERNAL = -1 > - unsigned int transition_latency = CPUFREQ_ETERNAL, will set it to UINT_MAX. > - Many drivers do it today > > cpufreq.c > > if (policy->governor->max_transition_latency && > policy->cpuinfo.transition_latency > > policy->governor->max_transition_latency) { > > - And this check will always fail, unless max_transition_latency is zero. > > What am I missing ? I don't know what's missing but I can reproduce the problem. -- ljk