From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prarit Bhargava Subject: [PATCH 2/2] cpufreq, intel_pstate, fix limits->max_perf rounding error Date: Fri, 20 Nov 2015 18:47:57 -0500 Message-ID: <1448063277-12446-3-git-send-email-prarit@redhat.com> References: <1448063277-12446-1-git-send-email-prarit@redhat.com> Return-path: Received: from mx1.redhat.com ([209.132.183.28]:34333 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422716AbbKTXsG (ORCPT ); Fri, 20 Nov 2015 18:48:06 -0500 In-Reply-To: <1448063277-12446-1-git-send-email-prarit@redhat.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org Cc: Prarit Bhargava , Srinivas Pandruvada , Len Brown , Alexandra Yates , Kristen Carlson Accardi , "Rafael J. Wysocki" , Viresh Kumar , linux-pm@vger.kernel.org A rounding error was found in the calculation of limits->max_perf in intel_pstate_set_policy(), which is used to calculate the max and min pstate values in intel_pstate_get_min_max(). In that code, limits->max_perf is truncated to 2 hex digits such that, for example, 0x169 was incorrectly calculated to 0x16 instead of 0x17. This resulted in the pstate being set one level too low. This patch rounds the value of limits->max_perf up instead of down so that the correct max pstate can be reached. Cc: Srinivas Pandruvada Cc: Len Brown Cc: Alexandra Yates Cc: Kristen Carlson Accardi Cc: "Rafael J. Wysocki" Cc: Viresh Kumar Cc: linux-pm@vger.kernel.org Signed-off-by: Prarit Bhargava --- drivers/cpufreq/intel_pstate.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index eb75053..8ad1f95 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -1121,6 +1121,7 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) limits->max_sysfs_pct); limits->max_perf_pct = max(limits->min_policy_pct, limits->max_perf_pct); + limits->max_perf = round_up(limits->max_perf, 8); /* Make sure min_perf_pct <= max_perf_pct */ limits->min_perf_pct = min(limits->max_perf_pct, limits->min_perf_pct); -- 1.8.3.1