From mboxrd@z Thu Jan 1 00:00:00 1970 From: Srinivas Pandruvada Subject: [PATCH v3 2/4] cpufreq: intel_pstate: Reduce impact due to rounding error Date: Tue, 25 Oct 2016 13:20:41 -0700 Message-ID: <1477426843-63821-3-git-send-email-srinivas.pandruvada@linux.intel.com> References: <1477426843-63821-1-git-send-email-srinivas.pandruvada@linux.intel.com> Return-path: Received: from mga01.intel.com ([192.55.52.88]:44577 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S941992AbcJYUU4 (ORCPT ); Tue, 25 Oct 2016 16:20:56 -0400 In-Reply-To: <1477426843-63821-1-git-send-email-srinivas.pandruvada@linux.intel.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: rjw@rjwysocki.net Cc: linux-pm@vger.kernel.org, Srinivas Pandruvada When policy->max and policy->min are same, in some cases they don't result in the same frequency cap. The max_policy_pct is rounded up but not min_perf_pct. So even when they are same, results in different percentage or maximum and minimum. Since minimum is a conservative value for power, a lower value without rounding is better in most of the cases, unless user wants policy->max = policy->min. This change uses use the same policy percentage when policy->max and policy->min are same. Signed-off-by: Srinivas Pandruvada --- drivers/cpufreq/intel_pstate.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index b6e9b49..8e7390b 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -1543,11 +1543,17 @@ static void intel_pstate_set_performance_limits(struct perf_limits *limits) static void intel_pstate_update_perf_limits(struct cpufreq_policy *policy, struct perf_limits *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 = DIV_ROUND_UP(policy->max * 100, policy->cpuinfo.max_freq); limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0, 100); + if (policy->max == policy->min) { + limits->min_policy_pct = limits->max_policy_pct; + } else { + limits->min_policy_pct = (policy->min * 100) / + policy->cpuinfo.max_freq; + limits->min_policy_pct = clamp_t(int, limits->min_policy_pct, + 0, 100); + } /* Normalize user input to [min_policy_pct, max_policy_pct] */ limits->min_perf_pct = max(limits->min_policy_pct, -- 2.7.4