Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933782AbcJLPgq (ORCPT ); Wed, 12 Oct 2016 11:36:46 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:60382 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752704AbcJLPgh (ORCPT ); Wed, 12 Oct 2016 11:36:37 -0400 DMARC-Filter: OpenDMARC Filter v1.3.1 smtp.codeaurora.org 567F8601B4 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=pass smtp.mailfrom=pprakash@codeaurora.org Subject: Re: [PATCH] cpufreq: CPPC: Correct desired_perf calculation To: Hoan Tran , "Rafael J. Wysocki" , Viresh Kumar , Al Stone References: <1476220320-19685-1-git-send-email-hotran@apm.com> Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, lho@apm.com, Duc Dang From: "Prakash, Prashanth" Message-ID: <507da442-1193-3b51-cae2-78779a90bb17@codeaurora.org> Date: Wed, 12 Oct 2016 09:36:34 -0600 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <1476220320-19685-1-git-send-email-hotran@apm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1195 Lines: 29 Hi Hoan, On 10/11/2016 3:12 PM, Hoan Tran wrote: > The desired_perf is an abstract performance number. Its value should > be in the range of [lowest perf, highest perf] of CPPC. > The correct calculation is > desired_perf = freq * cppc_highest_perf / cppc_dmi_max_khz > > Signed-off-by: Hoan Tran > --- > drivers/cpufreq/cppc_cpufreq.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c > index 1b2f28f..ab1d4b7 100644 > --- a/drivers/cpufreq/cppc_cpufreq.c > +++ b/drivers/cpufreq/cppc_cpufreq.c > @@ -84,7 +84,7 @@ static int cppc_cpufreq_set_target(struct cpufreq_policy *policy, > > cpu = all_cpu_data[policy->cpu]; > > - cpu->perf_ctrls.desired_perf = (u64)target_freq * policy->max / cppc_dmi_max_khz; > + cpu->perf_ctrls.desired_perf = (u64)target_freq * cpu->perf_caps.highest_perf / cppc_dmi_max_khz; The patch looks good, I suppose we can add a small optimization. We can do a simple check to see if the newly computed desired_perf is same as old one, If it is same we can just return here instead of calling cppc_set_perf with same desired_perf value. Thanks, Prashanth