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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 99A17C433E1 for ; Fri, 31 Jul 2020 12:14:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 77A612245C for ; Fri, 31 Jul 2020 12:14:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="bNVZRRmX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733114AbgGaMOU (ORCPT ); Fri, 31 Jul 2020 08:14:20 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:18970 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732784AbgGaMOS (ORCPT ); Fri, 31 Jul 2020 08:14:18 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Fri, 31 Jul 2020 05:12:44 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Fri, 31 Jul 2020 05:14:18 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Fri, 31 Jul 2020 05:14:18 -0700 Received: from [10.26.73.28] (172.20.13.39) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 31 Jul 2020 12:14:12 +0000 Subject: Re: [PATCH 1/2] cpufreq: tegra186: Fix initial frequency To: Viresh Kumar CC: Thierry Reding , "Rafael J . Wysocki" , , References: <20200712100645.13927-1-jonathanh@nvidia.com> <20200713032554.cykywnygxln6ukrl@vireshk-i7> <3d6091f2-6b04-185f-6c23-e39a34b87877@nvidia.com> <20200714034635.2zdv3wzmftjg2t4a@vireshk-i7> From: Jon Hunter Message-ID: <8c6d3c32-c142-3981-3a52-6560e885f4c9@nvidia.com> Date: Fri, 31 Jul 2020 13:14:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200714034635.2zdv3wzmftjg2t4a@vireshk-i7> X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1596197564; bh=y7zPiwOFyQtt0rLys/IwA3DQdByn03F5BY9HhZm1uGU=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=bNVZRRmX8+2ltVanZS1OMvKhphVdXl2odp8h+VQBK+Rwo/7AbIg5b3/oKCxt6q3Ky vhaxHJqlX1X3eQFeUvfgfurUP5sKw58bG0CayL5BDrcVgMDvQcRdNdVPSRlBdTekC4 zP0180OGr3VINBKhzwxQSgIvyrEoIofunWApjlz5IWzpsa3aG0Lmgk8UyKma1KfA9C uHBYDluv8wViENYf0tuf47ekrkut5EkiVzdF/+bSTBwdi2RAxtF5UXfqyUsyios84b 0Nh0iHe0swdwAjDplU8hn5nK+LTm+UUE+3PFxPJv+CQRSLn2flTyjc8HvuVztXMkqn llKsF3Gu5pGtg== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Viresh, On 14/07/2020 04:46, Viresh Kumar wrote: ... > The get() callback is supposed to read the frequency from hardware and > return it, no cached value here. policy->cur may end up being wrong in > case there is a bug. I have been doing some more testing on Tegra, I noticed that when reading the current CPU frequency via the sysfs scaling_cur_freq entry, this always returns the cached value (at least for Tegra). Looking at the implementation of scaling_cur_freq I see ... static ssize_t show_scaling_cur_freq(struct cpufreq_policy *policy, char *buf) { ssize_t ret; unsigned int freq; freq = arch_freq_get_on_cpu(policy->cpu); if (freq) ret = sprintf(buf, "%u\n", freq); else if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get) ret = sprintf(buf, "%u\n", cpufreq_driver->get(policy->cpu)); else ret = sprintf(buf, "%u\n", policy->cur); return ret; } The various Tegra CPU frequency drivers do not implement the set_policy callback and hence why we always get the cached value. I see the following commit added this and before it simply return the cached value ... commit c034b02e213d271b98c45c4a7b54af8f69aaac1e Author: Dirk Brandewie Date: Mon Oct 13 08:37:40 2014 -0700 cpufreq: expose scaling_cur_freq sysfs file for set_policy() drivers Is this intentional? Cheers Jon -- nvpublic