From patchwork Fri Jun 19 14:33:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 223678 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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 2DF09C433E1 for ; Fri, 19 Jun 2020 16:44:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D9992166E for ; Fri, 19 Jun 2020 16:44:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592585086; bh=GYEJjnVY8KxcLVgy66MTRYDQJ+J6hTQrdgqTAXH7Ni0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=tTI/JczN+FW+6AuaLsqTXDbCaQJNnjrvDRn8soZxaFCsTjZGQ+z294KgFxVsNIGgW 0dwWqiZuE1QlYDFFAFOZ/0KLjRckAB6wL+da1X/aqid4ljkko4DUs1u1Z5EYLVXZVI oYGDNzEp86uZuTJOq8kYUwL6eoPR7cfOyfb8Rsb0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391802AbgFSQol (ORCPT ); Fri, 19 Jun 2020 12:44:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:34016 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388431AbgFSOnE (ORCPT ); Fri, 19 Jun 2020 10:43:04 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E960E20CC7; Fri, 19 Jun 2020 14:43:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592577783; bh=GYEJjnVY8KxcLVgy66MTRYDQJ+J6hTQrdgqTAXH7Ni0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=j/5YlCcCjOUIZz0gRoSEvgeilLWc+hC4WEyIBAIapsGXvRpL4xgGYMddqDbZv3U68 /I0Icuy7AR8KmyuK/MTuKva7WTcdqI6s3QrS21J/dbyx4b4sf1nk8I+GScUCwdn91d VsVyTCWTrT+VVgyMuKMLYewJbXtStNCOpPh/7NWY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexey Malahov , Serge Semin , Jiaxun Yang , Thomas Bogendoerfer , Paul Burton , Ralf Baechle , Arnd Bergmann , Rob Herring , devicetree@vger.kernel.org, Sasha Levin Subject: [PATCH 4.9 086/128] mips: Add udelay lpj numbers adjustment Date: Fri, 19 Jun 2020 16:33:00 +0200 Message-Id: <20200619141624.692512845@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200619141620.148019466@linuxfoundation.org> References: <20200619141620.148019466@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Serge Semin [ Upstream commit ed26aacfb5f71eecb20a51c4467da440cb719d66 ] Loops-per-jiffies is a special number which represents a number of noop-loop cycles per CPU-scheduler quantum - jiffies. As you understand aside from CPU-specific implementation it depends on the CPU frequency. So when a platform has the CPU frequency fixed, we have no problem and the current udelay interface will work just fine. But as soon as CPU-freq driver is enabled and the cores frequency changes, we'll end up with distorted udelay's. In order to fix this we have to accordinly adjust the per-CPU udelay_val (the same as the global loops_per_jiffy) number. This can be done in the CPU-freq transition event handler. We subscribe to that event in the MIPS arch time-inititalization method. Co-developed-by: Alexey Malahov Signed-off-by: Alexey Malahov Signed-off-by: Serge Semin Reviewed-by: Jiaxun Yang Cc: Thomas Bogendoerfer Cc: Paul Burton Cc: Ralf Baechle Cc: Arnd Bergmann Cc: Rob Herring Cc: devicetree@vger.kernel.org Signed-off-by: Thomas Bogendoerfer Signed-off-by: Sasha Levin --- arch/mips/kernel/time.c | 70 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+) diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c index a7f81261c781..b7f7e08e1ce4 100644 --- a/arch/mips/kernel/time.c +++ b/arch/mips/kernel/time.c @@ -22,12 +22,82 @@ #include #include #include +#include +#include #include #include #include #include +#ifdef CONFIG_CPU_FREQ + +static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref); +static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref_freq); +static unsigned long glb_lpj_ref; +static unsigned long glb_lpj_ref_freq; + +static int cpufreq_callback(struct notifier_block *nb, + unsigned long val, void *data) +{ + struct cpufreq_freqs *freq = data; + struct cpumask *cpus = freq->policy->cpus; + unsigned long lpj; + int cpu; + + /* + * Skip lpj numbers adjustment if the CPU-freq transition is safe for + * the loops delay. (Is this possible?) + */ + if (freq->flags & CPUFREQ_CONST_LOOPS) + return NOTIFY_OK; + + /* Save the initial values of the lpjes for future scaling. */ + if (!glb_lpj_ref) { + glb_lpj_ref = boot_cpu_data.udelay_val; + glb_lpj_ref_freq = freq->old; + + for_each_online_cpu(cpu) { + per_cpu(pcp_lpj_ref, cpu) = + cpu_data[cpu].udelay_val; + per_cpu(pcp_lpj_ref_freq, cpu) = freq->old; + } + } + + /* + * Adjust global lpj variable and per-CPU udelay_val number in + * accordance with the new CPU frequency. + */ + if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || + (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) { + loops_per_jiffy = cpufreq_scale(glb_lpj_ref, + glb_lpj_ref_freq, + freq->new); + + for_each_cpu(cpu, cpus) { + lpj = cpufreq_scale(per_cpu(pcp_lpj_ref, cpu), + per_cpu(pcp_lpj_ref_freq, cpu), + freq->new); + cpu_data[cpu].udelay_val = (unsigned int)lpj; + } + } + + return NOTIFY_OK; +} + +static struct notifier_block cpufreq_notifier = { + .notifier_call = cpufreq_callback, +}; + +static int __init register_cpufreq_notifier(void) +{ + return cpufreq_register_notifier(&cpufreq_notifier, + CPUFREQ_TRANSITION_NOTIFIER); +} +core_initcall(register_cpufreq_notifier); + +#endif /* CONFIG_CPU_FREQ */ + /* * forward reference */