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 C571FC25B48 for ; Thu, 26 Oct 2023 09:05:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229642AbjJZJFk (ORCPT ); Thu, 26 Oct 2023 05:05:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59802 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229823AbjJZJFk (ORCPT ); Thu, 26 Oct 2023 05:05:40 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C99310E; Thu, 26 Oct 2023 02:05:35 -0700 (PDT) Received: from kwepemi500024.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4SGKZ81Y6Gz1L8xr; Thu, 26 Oct 2023 17:02:40 +0800 (CST) Received: from [10.174.179.163] (10.174.179.163) by kwepemi500024.china.huawei.com (7.221.188.100) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Thu, 26 Oct 2023 17:05:32 +0800 Message-ID: <438e230d-5169-32b3-3992-9fef5ba71f05@huawei.com> Date: Thu, 26 Oct 2023 17:05:31 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH 2/3] cpufreq: CPPC: Keep the target core awake when reading its cpufreq rate Content-Language: en-US To: Sudeep Holla CC: , , , , , , , , , , , , , , , , References: <20231025093847.3740104-1-zengheng4@huawei.com> <20231025093847.3740104-3-zengheng4@huawei.com> <20231025111301.ng5eaeaixfs3jjpg@bogus> From: Zeng Heng In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.163] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To kwepemi500024.china.huawei.com (7.221.188.100) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org 在 2023/10/26 16:53, Sudeep Holla 写道: > On Thu, Oct 26, 2023 at 10:24:54AM +0800, Zeng Heng wrote: >> 在 2023/10/25 19:13, Sudeep Holla 写道: >>> On Wed, Oct 25, 2023 at 05:38:46PM +0800, Zeng Heng wrote: >>>> As ARM AMU's document says, all counters are subject to any changes >>>> in clock frequency, including clock stopping caused by the WFI and WFE >>>> instructions. >>>> >>>> Therefore, using smp_call_on_cpu() to trigger target CPU to >>>> read self's AMU counters, which ensures the counters are working >>>> properly while cstate feature is enabled. >>>> >>>> Reported-by: Sumit Gupta >>>> Link: https://lore.kernel.org/all/20230418113459.12860-7-sumitg@nvidia.com/ >>>> Signed-off-by: Zeng Heng >>>> --- >>>> drivers/cpufreq/cppc_cpufreq.c | 39 ++++++++++++++++++++++++++-------- >>>> 1 file changed, 30 insertions(+), 9 deletions(-) >>>> >>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c >>>> index fe08ca419b3d..321a9dc9484d 100644 >>>> --- a/drivers/cpufreq/cppc_cpufreq.c >>>> +++ b/drivers/cpufreq/cppc_cpufreq.c >>> [...] >>> >>>> @@ -850,18 +871,18 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpu) >>>> cpufreq_cpu_put(policy); >>>> - ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t0); >>>> - if (ret) >>>> - return 0; >>>> - >>>> - udelay(2); /* 2usec delay between sampling */ >>>> + if (cpu_has_amu_feat(cpu)) >>> Have you compiled this on x86 ? Even if you have somehow managed to, >>> this is not the right place to check the presence of AMU feature on >>> the CPU. >>> If AMU registers are used in CPPC, they must be using FFH GAS, in which >>> case the interpretation of FFH is architecture dependent code. >> According to drivers/cpufreq/Makefile, cppc_cpufreq.c is only compiled with >> ARM architecture. >> > Well that's true but this change doesn't belong to cppc_cpufreq.c, it must > be part of drivers/acpi/cppc_acpi.c IMO and sorry I assumed that without > explicitly mentioning that here. > >> But here, I would change cpu_has_amu_feat() with cpc_ffh_supported(), which >> belongs to FFH APIs. >> > It is not like that. cppc_acpi.c will know the GAS is FFH based so no need to > check anything there. I see counters_read_on_cpu() called from cpc_ffh_read() > already takes care of reading the AMUs on the right CPU. What exactly is > the issue you are seeing ? I don't if this change is needed at all. > > -- > Regards, > Sudeep In this scenario, both topology.c and cppc_acpi.c do not provide an API to keep the AMU online during the whole sampling period. Just using cpc_read_ffh() at the start and end of the sampling period is not enough. Zeng Heng