Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1033578AbbKFTg6 (ORCPT ); Fri, 6 Nov 2015 14:36:58 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:47979 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031359AbbKFTcu (ORCPT ); Fri, 6 Nov 2015 14:32:50 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Srinivas Pandruvada , Kristen Carlson Accardi , "Rafael J. Wysocki" Subject: [PATCH 4.1 75/86] cpufreq: intel_pstate: Fix divide by zero on Knights Landing (KNL) Date: Fri, 6 Nov 2015 11:23:14 -0800 Message-Id: <20151106192209.021255279@linuxfoundation.org> X-Mailer: git-send-email 2.6.2 In-Reply-To: <20151106192205.351595349@linuxfoundation.org> References: <20151106192205.351595349@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1499 Lines: 44 4.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Srinivas Pandruvada commit 8e601a9f97a00bab031980de34f9a81891c1f82f upstream. 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. Fixes: b34ef932d79a (intel_pstate: Knights Landing support) Signed-off-by: Srinivas Pandruvada Acked-by: Kristen Carlson Accardi Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- drivers/cpufreq/intel_pstate.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -761,6 +761,11 @@ static inline void intel_pstate_sample(s local_irq_save(flags); rdmsrl(MSR_IA32_APERF, aperf); rdmsrl(MSR_IA32_MPERF, mperf); + if (cpu->prev_mperf == mperf) { + local_irq_restore(flags); + return; + } + local_irq_restore(flags); cpu->last_sample_time = cpu->sample.time; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/