From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752982Ab3LBFey (ORCPT ); Mon, 2 Dec 2013 00:34:54 -0500 Received: from mail-qa0-f45.google.com ([209.85.216.45]:32875 "EHLO mail-qa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752865Ab3LBFei (ORCPT ); Mon, 2 Dec 2013 00:34:38 -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 V2 5/5] cpufreq: unicore2: send new set of notification for transition failures Date: Mon, 2 Dec 2013 11:04:16 +0530 Message-Id: X-Mailer: git-send-email 1.7.12.rc2.18.g61b472e In-Reply-To: References: In-Reply-To: References: 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. Also it returns a proper error message in case frequency transition failed. Signed-off-by: Viresh Kumar --- drivers/cpufreq/unicore2-cpufreq.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/drivers/cpufreq/unicore2-cpufreq.c b/drivers/cpufreq/unicore2-cpufreq.c index 951152f..99d280d6 100644 --- a/drivers/cpufreq/unicore2-cpufreq.c +++ b/drivers/cpufreq/unicore2-cpufreq.c @@ -38,19 +38,17 @@ static int ucv2_target(struct cpufreq_policy *policy, unsigned int target_freq, unsigned int relation) { - unsigned int cur = policy->cur; struct cpufreq_freqs freqs; + int ret; - cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE); - - if (!clk_set_rate(policy->clk, target_freq * 1000)) { - freqs.old = cur; - freqs.new = target_freq; - } + freqs.old = policy->cur; + freqs.new = target_freq; - cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE); + cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE); + ret = clk_set_rate(policy->clk, target_freq * 1000); + cpufreq_notify_post_transition(policy, &freqs, ret); - return 0; + return ret; } static int __init ucv2_cpu_init(struct cpufreq_policy *policy) -- 1.7.12.rc2.18.g61b472e