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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08173C433EF for ; Mon, 30 May 2022 08:45:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231971AbiE3IpR (ORCPT ); Mon, 30 May 2022 04:45:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57718 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234072AbiE3IpE (ORCPT ); Mon, 30 May 2022 04:45:04 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D30684D601; Mon, 30 May 2022 01:45:01 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9A5E9113E; Mon, 30 May 2022 01:45:01 -0700 (PDT) Received: from [192.168.1.11] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 774C93F73D; Mon, 30 May 2022 01:45:00 -0700 (PDT) Message-ID: <3a26ce90-5d2d-0164-3799-85a9dc1abee6@arm.com> Date: Mon, 30 May 2022 10:44:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH v1] cpufreq: CPPC: Fix unused-function warning Content-Language: en-US To: Viresh Kumar Cc: linux-kernel@vger.kernel.org, Ionela.Voinescu@arm.com, Dietmar.Eggemann@arm.com, Shaokun Zhang , "Rafael J. Wysocki" , linux-pm@vger.kernel.org References: <20220530081236.40728-1-pierre.gondois@arm.com> <20220530082025.vqzk37dvyzxiq7dv@vireshk-i7> From: Pierre Gondois In-Reply-To: <20220530082025.vqzk37dvyzxiq7dv@vireshk-i7> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 5/30/22 10:20, Viresh Kumar wrote: > On 30-05-22, 10:12, Pierre Gondois wrote: >> Building the cppc_cpufreq driver with for arm64 with >> CONFIG_ENERGY_MODEL=n triggers the following warnings: >> drivers/cpufreq/cppc_cpufreq.c:550:12: error: ‘cppc_get_cpu_cost’ defined but not used >> [-Werror=unused-function] >> 550 | static int cppc_get_cpu_cost(struct device *cpu_dev, unsigned long KHz, >> | ^~~~~~~~~~~~~~~~~ >> drivers/cpufreq/cppc_cpufreq.c:481:12: error: ‘cppc_get_cpu_power’ defined but not used >> [-Werror=unused-function] >> 481 | static int cppc_get_cpu_power(struct device *cpu_dev, >> | ^~~~~~~~~~~~~~~~~~ >> >> Fixes: 740fcdc2c20e ("cpufreq: CPPC: Register EM based on efficiency class information") >> Reported-by: Shaokun Zhang >> Signed-off-by: Pierre Gondois >> --- >> drivers/cpufreq/cppc_cpufreq.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c >> index d092c9bb4ba3..ecd0d3ee48c5 100644 >> --- a/drivers/cpufreq/cppc_cpufreq.c >> +++ b/drivers/cpufreq/cppc_cpufreq.c >> @@ -478,7 +478,7 @@ static inline unsigned long compute_cost(int cpu, int step) >> step * CPPC_EM_COST_STEP; >> } >> >> -static int cppc_get_cpu_power(struct device *cpu_dev, >> +static __maybe_unused int cppc_get_cpu_power(struct device *cpu_dev, >> unsigned long *power, unsigned long *KHz) >> { >> unsigned long perf_step, perf_prev, perf, perf_check; >> @@ -547,8 +547,8 @@ static int cppc_get_cpu_power(struct device *cpu_dev, >> return 0; >> } >> >> -static int cppc_get_cpu_cost(struct device *cpu_dev, unsigned long KHz, >> - unsigned long *cost) >> +static __maybe_unused int cppc_get_cpu_cost(struct device *cpu_dev, >> + unsigned long KHz, unsigned long *cost) >> { >> unsigned long perf_step, perf_prev; >> struct cppc_perf_caps *perf_caps; > > Should we actually run cppc_cpufreq_register_em() for > !CONFIG_ENERGY_MODEL ? Why? > Hello Viresh, It seems that when CONFIG_ENERGY_MODEL=n, the compiler is already considering cppc_cpufreq_register_em() as an empty function. Indeed, CONFIG_ENERGY_MODEL=n makes em_dev_register_perf_domain() an empty function, so cppc_cpufreq_register_em() is only made of variable definitions. This compiler optimization also explains why cppc_get_cpu_power() and cppc_get_cpu_cost() trigger the -Wunused-function warning. Putting cppc_cpufreq_register_em() inside an #ifdef CONFIG_ENERGY_MODEL guard seems also valid to me. To avoid too many empty definitions of cppc_cpufreq_register_em(), I guess it should be inside an #if defined(CONFIG_ARM64) && defined(CONFIG_ENERGY_MODEL) guard instead. Please let me know what you prefer. Regards, Pierre