Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752542AbaDYInD (ORCPT ); Fri, 25 Apr 2014 04:43:03 -0400 Received: from e28smtp09.in.ibm.com ([122.248.162.9]:60293 "EHLO e28smtp09.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751717AbaDYIm6 (ORCPT ); Fri, 25 Apr 2014 04:42:58 -0400 Message-ID: <535A1FE2.3080703@linux.vnet.ibm.com> Date: Fri, 25 Apr 2014 14:12:10 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: Viresh Kumar CC: "Rafael J. Wysocki" , Meelis Roos , "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List Subject: Re: [PATCH 2/3] cpufreq, powernow-k6: Fix double invocation of cpufreq_freq_transition_begin/end References: <20140425081728.10258.63980.stgit@srivatsabhat.in.ibm.com> <20140425081815.10258.36201.stgit@srivatsabhat.in.ibm.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14042508-2674-0000-0000-00000DF57EFA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/25/2014 01:58 PM, Viresh Kumar wrote: > On 25 April 2014 13:48, Srivatsa S. Bhat > wrote: >> During frequency transitions, the cpufreq core takes the responsibility of >> invoking cpufreq_freq_transition_begin() and cpufreq_freq_transition_end() >> for those cpufreq drivers that define the ->target_index callback but don't >> set the ASYNC_NOTIFICATION flag. >> >> The powernow-k6 cpufreq driver falls under this category, but this driver was >> invoking the _begin() and _end() APIs itself around frequency transitions, >> which led to double invocation of the _begin() API. The _begin API makes >> contending callers wait until the previous invocation is complete. Hence, >> the powernow-k6 driver ended up waiting on itself, leading to system hangs >> during boot. >> >> Fix this by removing the calls to the _begin() and _end() APIs from the >> powernow-k6 driver, since they rightly belong to the cpufreq core. >> >> (Note that during ->exit(), the powernow-k6 driver sets the frequency >> without any help from the cpufreq core. So add explicit calls to the >> _begin() and _end() APIs around that frequency transition alone, to take >> care of that special case. Also, add a missing 'break' statement there.) >> >> Signed-off-by: Srivatsa S. Bhat >> --- >> >> drivers/cpufreq/powernow-k6.c | 20 +++++++++++--------- >> 1 file changed, 11 insertions(+), 9 deletions(-) >> >> diff --git a/drivers/cpufreq/powernow-k6.c b/drivers/cpufreq/powernow-k6.c >> index 49f120e..6a4c34e 100644 >> --- a/drivers/cpufreq/powernow-k6.c >> +++ b/drivers/cpufreq/powernow-k6.c >> @@ -138,22 +138,14 @@ static void powernow_k6_set_cpu_multiplier(unsigned int best_i) >> static int powernow_k6_target(struct cpufreq_policy *policy, >> unsigned int best_i) >> { >> - struct cpufreq_freqs freqs; >> >> if (clock_ratio[best_i].driver_data > max_multiplier) { >> printk(KERN_ERR PFX "invalid target frequency\n"); >> return -EINVAL; >> } >> >> - freqs.old = busfreq * powernow_k6_get_cpu_multiplier(); >> - freqs.new = busfreq * clock_ratio[best_i].driver_data; >> - >> - cpufreq_freq_transition_begin(policy, &freqs); >> - >> powernow_k6_set_cpu_multiplier(best_i); >> >> - cpufreq_freq_transition_end(policy, &freqs, 0); >> - >> return 0; >> } >> >> @@ -228,8 +220,18 @@ static int powernow_k6_cpu_exit(struct cpufreq_policy *policy) >> { >> unsigned int i; >> for (i = 0; i < 8; i++) { >> - if (i == max_multiplier) >> + if (i == max_multiplier) { > > This wouldn't work, it has to be: (clock_ratio[i].driver_data == max_multiplier) > Hmm, looks like an existing bug in the driver. Will fix this in the next version. Regards, Srivatsa S. Bhat >> + struct cpufreq_freqs freqs; >> + >> + freqs.old = policy->cur; >> + freqs.new = clock_ratio[i].frequency; >> + freqs.flags = 0; >> + >> + cpufreq_freq_transition_begin(policy, &freqs); >> powernow_k6_target(policy, i); >> + cpufreq_freq_transition_end(policy, &freqs, 0); >> + break; >> + } >> } >> return 0; >> } > > Acked-by: Viresh Kumar > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/