Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755875AbcJLRfa (ORCPT ); Wed, 12 Oct 2016 13:35:30 -0400 Received: from mail-vk0-f49.google.com ([209.85.213.49]:35494 "EHLO mail-vk0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755803AbcJLRfV (ORCPT ); Wed, 12 Oct 2016 13:35:21 -0400 MIME-Version: 1.0 In-Reply-To: <507da442-1193-3b51-cae2-78779a90bb17@codeaurora.org> References: <1476220320-19685-1-git-send-email-hotran@apm.com> <507da442-1193-3b51-cae2-78779a90bb17@codeaurora.org> From: Hoan Tran Date: Wed, 12 Oct 2016 10:33:48 -0700 Message-ID: Subject: Re: [PATCH] cpufreq: CPPC: Correct desired_perf calculation To: "Prakash, Prashanth" Cc: "Rafael J. Wysocki" , Viresh Kumar , Al Stone , linux-pm@vger.kernel.org, lkml , Loc Ho , Duc Dang Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1441 Lines: 41 [Resend with plain text mode] Hi Prashanth, On Wed, Oct 12, 2016 at 8:36 AM, Prakash, Prashanth wrote: > 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. That's a good point. I can add a check into this patch. Thanks Hoan > > Thanks, > Prashanth