From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753025Ab3K3P46 (ORCPT ); Sat, 30 Nov 2013 10:56:58 -0500 Received: from mail-pd0-f175.google.com ([209.85.192.175]:37821 "EHLO mail-pd0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752950Ab3K3P4y (ORCPT ); Sat, 30 Nov 2013 10:56:54 -0500 From: Viresh Kumar To: rjw@rjwysocki.net Cc: linaro-kernel@lists.linaro.org, patches@linaro.org, cpufreq@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Viresh Kumar Subject: [PATCH 4/5] cpufreq: powernow-k8: send new set of notification for transition failures Date: Sat, 30 Nov 2013 21:26:22 +0530 Message-Id: X-Mailer: git-send-email 1.7.12.rc2.18.g61b472e In-Reply-To: <0d635c6701654a75f6d25dd435705dc1ede3e19c.1385826776.git.viresh.kumar@linaro.org> References: <0d635c6701654a75f6d25dd435705dc1ede3e19c.1385826776.git.viresh.kumar@linaro.org> In-Reply-To: <0d635c6701654a75f6d25dd435705dc1ede3e19c.1385826776.git.viresh.kumar@linaro.org> References: <0d635c6701654a75f6d25dd435705dc1ede3e19c.1385826776.git.viresh.kumar@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In the current code, if we fail during a frequency transition we simply send the POSTCHANGE notification with old frequency. This isn't enough. One of the core user of these notifications is the code responsible for keeping loops_per_jiffy aligned with frequency change. And mostly it is written as: if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) { update-loops-per-jiffy... } So, suppose we are changing to a higher frequency and failed during transition, then following will happen: - CPUFREQ_PRECHANGE notification with freq-new > freq-old - CPUFREQ_POSTCHANGE notification with freq-new == freq-old The first one will update loops_per_jiffy and second one will do nothing. Even if we send the 2nd notification by exchanging values of freq-new and old, some users of these notifications might get unstable. This can be fixed by simply calling cpufreq_notify_post_transition() with error code and this routine will take care of sending notifications in correct order. Signed-off-by: Viresh Kumar --- drivers/cpufreq/powernow-k8.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c index 0023c7d..e10b646 100644 --- a/drivers/cpufreq/powernow-k8.c +++ b/drivers/cpufreq/powernow-k8.c @@ -964,14 +964,9 @@ static int transition_frequency_fidvid(struct powernow_k8_data *data, cpufreq_cpu_put(policy); cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE); - res = transition_fid_vid(data, fid, vid); - if (res) - freqs.new = freqs.old; - else - freqs.new = find_khz_freq_from_fid(data->currfid); + cpufreq_notify_post_transition(policy, &freqs, res); - cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE); return res; } -- 1.7.12.rc2.18.g61b472e