Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752524AbaDYI2c (ORCPT ); Fri, 25 Apr 2014 04:28:32 -0400 Received: from mail-oa0-f49.google.com ([209.85.219.49]:33120 "EHLO mail-oa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751835AbaDYI22 (ORCPT ); Fri, 25 Apr 2014 04:28:28 -0400 MIME-Version: 1.0 In-Reply-To: <20140425081815.10258.36201.stgit@srivatsabhat.in.ibm.com> References: <20140425081728.10258.63980.stgit@srivatsabhat.in.ibm.com> <20140425081815.10258.36201.stgit@srivatsabhat.in.ibm.com> Date: Fri, 25 Apr 2014 13:58:27 +0530 Message-ID: Subject: Re: [PATCH 2/3] cpufreq, powernow-k6: Fix double invocation of cpufreq_freq_transition_begin/end From: Viresh Kumar To: "Srivatsa S. Bhat" Cc: "Rafael J. Wysocki" , Meelis Roos , "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) > + 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/