From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dirk Brandewie Subject: Re: [PATCH] cpufreq: Skip current frequency initialization for ->setpolicy drivers Date: Wed, 12 Mar 2014 16:30:44 -0700 Message-ID: <5320EE24.4030005@gmail.com> References: <2460637.PSm5Ca8pqs@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pb0-f50.google.com ([209.85.160.50]:63974 "EHLO mail-pb0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751767AbaCLXiJ (ORCPT ); Wed, 12 Mar 2014 19:38:09 -0400 In-Reply-To: <2460637.PSm5Ca8pqs@vostro.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" , Patrik Lundquist Cc: dirk.brandewie@gmail.com, "cpufreq@vger.kernel.org" , Linux PM list On 03/12/2014 04:30 PM, Rafael J. Wysocki wrote: > Dirk, please let me know if you're fine with it. > > --- > From: Rafael J. Wysocki > Subject: cpufreq: Skip current frequency initialization for ->setpolicy drivers > > After commit da60ce9f2fac (cpufreq: call cpufreq_driver->get() after > calling ->init()) __cpufreq_add_dev() sometimes fails for CPUs handled > by intel_pstate, because that driver may return 0 from its ->get() > callback if it has not run long enough to collect enough samples on the > given CPU. That didn't happen before commit da60ce9f2fac which added > policy->cur initialization to __cpufreq_add_dev() to help reduce code > duplication in other cpufreq drivers. > > However, the code added by commit da60ce9f2fac need not be executed > for cpufreq drivers having the ->setpolicy callback defined, because > the subsequent invocation of cpufreq_set_policy() will use that > callback to initialize the policy anyway and it doesn't need > policy->cur to be initialized upfront. The analogous code in > cpufreq_update_policy() is also unnecessary for cpufreq drivers > having ->setpolicy set and may be skipped for them as well. > > Since intel_pstate provides ->setpolicy, skipping the upfront > policy->cur initialization for cpufreq drivers with that callback > set will cover intel_pstate and the problem it's been having after > commit da60ce9f2fac will be addressed. > > Fixes: da60ce9f2fac (cpufreq: call cpufreq_driver->get() after calling ->init()) > References: https://bugzilla.kernel.org/show_bug.cgi?id=71931 > Reported-and-tested-by: Patrik Lundquist > Signed-off-by: Rafael J. Wysocki Acked-by: Dirk Brandewie > Cc: 3.13+ # 3.13+ > --- > drivers/cpufreq/cpufreq.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > Index: linux-pm/drivers/cpufreq/cpufreq.c > =================================================================== > --- linux-pm.orig/drivers/cpufreq/cpufreq.c > +++ linux-pm/drivers/cpufreq/cpufreq.c > @@ -1129,7 +1129,7 @@ static int __cpufreq_add_dev(struct devi > per_cpu(cpufreq_cpu_data, j) = policy; > write_unlock_irqrestore(&cpufreq_driver_lock, flags); > > - if (cpufreq_driver->get) { > + if (cpufreq_driver->get && !cpufreq_driver->setpolicy) { > policy->cur = cpufreq_driver->get(policy->cpu); > if (!policy->cur) { > pr_err("%s: ->get() failed\n", __func__); > @@ -2143,7 +2143,7 @@ int cpufreq_update_policy(unsigned int c > * BIOS might change freq behind our back > * -> ask driver for current freq and notify governors about a change > */ > - if (cpufreq_driver->get) { > + if (cpufreq_driver->get && !cpufreq_driver->setpolicy) { > new_policy.cur = cpufreq_driver->get(cpu); > if (!policy->cur) { > pr_debug("Driver did not initialize current freq"); >