From patchwork Thu Oct 15 19:34:21 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: srinivas pandruvada X-Patchwork-Id: 7409031 X-Patchwork-Delegate: rjw@sisk.pl Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id DBF049F302 for ; Thu, 15 Oct 2015 19:35:03 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 2A7392078D for ; Thu, 15 Oct 2015 19:35:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9D0B0207BA for ; Thu, 15 Oct 2015 19:35:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752069AbbJOTfA (ORCPT ); Thu, 15 Oct 2015 15:35:00 -0400 Received: from mga09.intel.com ([134.134.136.24]:28094 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752145AbbJOTe7 (ORCPT ); Thu, 15 Oct 2015 15:34:59 -0400 Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga102.jf.intel.com with ESMTP; 15 Oct 2015 12:34:58 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,687,1437462000"; d="scan'208";a="665216198" Received: from spandruv-desk3.jf.intel.com ([10.7.199.153]) by orsmga003.jf.intel.com with ESMTP; 15 Oct 2015 12:34:58 -0700 From: Srinivas Pandruvada To: kristen.c.accardi@intel.com, rafael.j.wysocki@intel.com, len.brown@intel.com Cc: linux-pm@vger.kernel.org, Srinivas Pandruvada Subject: [PATCH v1] cpufreq: intel_pstate: divide by zero on Knights Landing (KNL) Date: Thu, 15 Oct 2015 12:34:21 -0700 Message-Id: <1444937661-9519-2-git-send-email-srinivas.pandruvada@linux.intel.com> X-Mailer: git-send-email 1.9.3 In-Reply-To: <1444937661-9519-1-git-send-email-srinivas.pandruvada@linux.intel.com> References: <1444937661-9519-1-git-send-email-srinivas.pandruvada@linux.intel.com> Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This is a workaround for KNL platform, where in some cases MPERF counter will not have updated value before next read of MSR_IA32_MPERF. In this case divide by zero will occur. This change ignores current sample for busy calculation in this case. Signed-off-by: Srinivas Pandruvada Acked-by: Kristen Carlson Accardi --- drivers/cpufreq/intel_pstate.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 3af9dd7..aa33b92 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -776,6 +776,11 @@ static inline void intel_pstate_sample(struct cpudata *cpu) local_irq_save(flags); rdmsrl(MSR_IA32_APERF, aperf); rdmsrl(MSR_IA32_MPERF, mperf); + if (cpu->prev_mperf == mperf) { + local_irq_restore(flags); + return; + } + tsc = rdtsc(); local_irq_restore(flags);