From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prarit Bhargava Subject: [PATCH 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error Date: Fri, 20 Nov 2015 18:47:56 -0500 Message-ID: <1448063277-12446-2-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]:40405 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422692AbbKTXsF (ORCPT ); Fri, 20 Nov 2015 18:48:05 -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 I have a Intel (6,63) processor with a "marketing" frequency (from /proc/cpuinfo) of 2100MHz, and a max turbo frequency of 2600MHz. I can execute cpupower frequency-set -g powersave --min 1200MHz --max 2100MHz and the max_freq_pct is set to 80. When adding load to the system I noticed that the cpu frequency only reached 2000MHZ and not 2100MHz as expected. This is because limits->max_policy_pct is calculated as 2100 * 100 /2600 = 80.7 and is rounded down to 80 when it should be rounded up to 81. This patch adds a DIV_ROUND_UP() which will return the correct value. 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 | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 001a532..eb75053 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -1108,7 +1108,8 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) limits = &powersave_limits; limits->min_policy_pct = (policy->min * 100) / policy->cpuinfo.max_freq; limits->min_policy_pct = clamp_t(int, limits->min_policy_pct, 0 , 100); - limits->max_policy_pct = (policy->max * 100) / policy->cpuinfo.max_freq; + limits->max_policy_pct = DIV_ROUND_UP(policy->max * 100, + policy->cpuinfo.max_freq); limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0 , 100); /* Normalize user input to [min_policy_pct, max_policy_pct] */ -- 1.8.3.1