From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 092CAC433F5 for ; Thu, 6 Sep 2018 13:18:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C231B2075B for ; Thu, 6 Sep 2018 13:17:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C231B2075B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729267AbeIFRx1 (ORCPT ); Thu, 6 Sep 2018 13:53:27 -0400 Received: from foss.arm.com ([217.140.101.70]:45526 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728724AbeIFRx0 (ORCPT ); Thu, 6 Sep 2018 13:53:26 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 87ACA80D; Thu, 6 Sep 2018 06:17:57 -0700 (PDT) Received: from queper01-lin (queper01-lin.Emea.Arm.com [10.4.13.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 05E8D3F575; Thu, 6 Sep 2018 06:17:55 -0700 (PDT) Date: Thu, 6 Sep 2018 14:17:54 +0100 From: Quentin Perret To: Sudeep Holla Cc: arm@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Ionela Voinescu , Kevin Hilman , Olof Johansson , Arnd Bergmann Subject: Re: [PATCH] firmware: arm_scmi: fix divide by zero when sustained_perf_level is zero Message-ID: <20180906131752.ysubfiufocddpoey@queper01-lin> References: <1536165491-27813-1-git-send-email-sudeep.holla@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1536165491-27813-1-git-send-email-sudeep.holla@arm.com> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sudeep, On Wednesday 05 Sep 2018 at 17:38:11 (+0100), Sudeep Holla wrote: > @@ -166,7 +166,12 @@ scmi_perf_domain_attributes_get(const struct scmi_handle *handle, u32 domain, > le32_to_cpu(attr->sustained_freq_khz); > dom_info->sustained_perf_level = > le32_to_cpu(attr->sustained_perf_level); > - dom_info->mult_factor = (dom_info->sustained_freq_khz * 1000) / > + if (!dom_info->sustained_freq_khz || > + !dom_info->sustained_perf_level) > + dom_info->mult_factor = 1; I'm sorry I missed that the first time I reviewed this patch, but after discussing with Ionela, we found out that there is actually a case where this could be a problem. If you have perf levels that are 1,2,3,4 (for example), then with mult_factor=1 you'll register OPPs at 1Hz, 2Hz, 3Hz, 4Hz into PM_OPP. And that will be turned into 0 KHz for all of them at the CPUFreq level when divided by 1000 in dev_pm_opp_init_cpufreq_table(). I guess a quick fix would be to have a default mult_factor of 1000 ... What do you think ? Thanks, Quentin