From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga05-in.huawei.com (szxga05-in.huawei.com [45.249.212.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A06C8EC2; Mon, 4 Aug 2025 06:31:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.191 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754289083; cv=none; b=JA1hVgV5ABXx4hgW+76MwZEVqiXXPrV5c6lyKEz2XROKPYU6i9ybVXK94/zT3iMSJI1LxvksUPrZIEQjGfexKkC1K2mls2U/N7/xOSbfF2/CHRZ/m/kiWIN/N7GCIwesQFh7Ym0sTjlgiCR7gsN605m1rkhSa0EyVpnsuGrd2GI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754289083; c=relaxed/simple; bh=gFIHgnOsz/b8h8EXosQD4sDckTrb5J/yBlKjPa9pFLI=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=psWaMT9/QewR/ToXNQEFPHKHKwxc83E1OrZlt+rswJw1FRLJzMozPLrZs+Z/EZVitlDEdG+/MzxVVOcYmc3/e1K1jOY1QZkk068O5+G6zjZ+9KBOT1aQhrCNGoeeErU01FQWNEpuXG9iAe4lHc6kKsTwpYqS1bCCig+P9ihF4Gc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=hisilicon.com; spf=pass smtp.mailfrom=hisilicon.com; arc=none smtp.client-ip=45.249.212.191 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=hisilicon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=hisilicon.com Received: from mail.maildlp.com (unknown [172.19.162.112]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4bwRTY4RLHz23jdk; Mon, 4 Aug 2025 14:28:49 +0800 (CST) Received: from kwepemo100006.china.huawei.com (unknown [7.202.195.47]) by mail.maildlp.com (Postfix) with ESMTPS id A51651400D6; Mon, 4 Aug 2025 14:31:17 +0800 (CST) Received: from [10.67.121.58] (10.67.121.58) by kwepemo100006.china.huawei.com (7.202.195.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 4 Aug 2025 14:31:16 +0800 Message-ID: <0ce0acbc-99da-925e-145d-3c80558be761@hisilicon.com> Date: Mon, 4 Aug 2025 14:31:16 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.3.2 Subject: Re: [PATCH 2/2] cpufreq: CPPC: Fix error handling in cppc_scale_freq_workfn() To: Beata Michalska CC: Bowen Yu , , , , , , , , References: <20250730032312.167062-1-yubowen8@huawei.com> <20250730032312.167062-3-yubowen8@huawei.com> From: Jie Zhan In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To kwepemo100006.china.huawei.com (7.202.195.47) On 31/07/2025 17:42, Beata Michalska wrote: > On Thu, Jul 31, 2025 at 04:52:05PM +0800, Jie Zhan wrote: >> >> >> On 31/07/2025 16:19, Beata Michalska wrote: >>> Hi Bowen, Jie >>> On Wed, Jul 30, 2025 at 11:23:12AM +0800, Bowen Yu wrote: >>>> From: Jie Zhan >>>> >>>> Perf counters could be 0 if the cpu is in a low-power idle state. Just try >>>> it again next time and update the frequency scale when the cpu is active >>>> and perf counters successfully return. >>>> >>>> Also, remove the FIE source on an actual failure. >>>> >>>> Signed-off-by: Jie Zhan >>>> --- >>>> drivers/cpufreq/cppc_cpufreq.c | 13 ++++++++++++- >>>> 1 file changed, 12 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c >>>> index 904006027df2..e95844d3d366 100644 >>>> --- a/drivers/cpufreq/cppc_cpufreq.c >>>> +++ b/drivers/cpufreq/cppc_cpufreq.c >>>> @@ -78,12 +78,23 @@ static void cppc_scale_freq_workfn(struct kthread_work *work) >>>> struct cppc_cpudata *cpu_data; >>>> unsigned long local_freq_scale; >>>> u64 perf; >>>> + int ret; >>>> >>>> cppc_fi = container_of(work, struct cppc_freq_invariance, work); >>>> cpu_data = cppc_fi->cpu_data; >>>> >>>> - if (cppc_get_perf_ctrs(cppc_fi->cpu, &fb_ctrs)) { >>>> + ret = cppc_get_perf_ctrs(cppc_fi->cpu, &fb_ctrs); >>>> + /* >>>> + * Perf counters could be 0 if the cpu is in a low-power idle state. >>>> + * Just try it again next time. >>>> + */ >>>> + if (ret == -EFAULT) >>>> + return; >>> Which counters are we actually talking about here ? >> >> Delivered performance counter and reference performance counter. >> They are actually AMU CPU_CYCLES and CNT_CYCLES event counters. > That does track then. >> >>>> + >>>> + if (ret) { >>>> pr_warn("%s: failed to read perf counters\n", __func__); >>>> + topology_clear_scale_freq_source(SCALE_FREQ_SOURCE_CPPC, >>>> + cpu_data->shared_cpu_map); >>>> return; >>>> } >>> And the real error here would be ... ? >>> That makes me wonder why this has been registered as the source of the freq >>> scale in the first place if we are to hit some serious issue. Would you be able >>> to give an example of any? >> If it gets here, that would be -ENODEV or -EIO from cppc_get_perf_ctrs(), >> which could possibly come from data corruption (no CPC descriptor) or a PCC >> failure. >> >> I can't easily fake an error here, but the above -EFAULT path could >> happen when it luckily passes the FIE init. >> > The change seems reasonable. Though I am wondering if some other errors might be > rather transient as well ? Like -EIO ? > Note, I'm not an expert here. The -EIO from PCC contains much more error cases than this.