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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 26245C43458 for ; Mon, 29 Jun 2026 15:55:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:MIME-Version: Content-Transfer-Encoding:Content-Type:In-Reply-To:From:References:Cc:To: Subject:Date:Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/NhZ5wJy1LRqxbpyNv5WxkQxP9cGKNEzDf6JbFacEV8=; b=QC3PJLUD28Lg+GQmKvTXicY2Ev uGt2ncq2lS1QJfUkeEexzXBr7yUpwSlH3K1k32aBvNvhd5MJMysCwv/xBAqkFsvc/3SQHp4/9Bilf jw5YhJ7YYpXhOf+ARESLC7EW+OT4v3ZtoEoBRbGiO5yFlVT7z351ul7ZvPPmF3QybuViPlK4l1COn ONz4dc/mo97gklRxknBPtYca1IINfMTXp/1u4nbl8k01SDAvbR1iqL6fvKfidmrhFqIbL2z8oO57U 6egTtT2j8ahdKYNU0QLf2OqFr8FC19sPkNs2fbDXb8oHGNv8gva5ntRObAakx+cY2FTYLLCJyMYW3 MG+droCg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1weEKC-0000000F8bn-2pPk; Mon, 29 Jun 2026 15:55:08 +0000 Received: from mail-westcentralusazon11013057.outbound.protection.outlook.com ([40.93.201.57] helo=CY3PR05CU001.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1weEK9-0000000F8bD-31oV for linux-arm-kernel@lists.infradead.org; Mon, 29 Jun 2026 15:55:08 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=VHyavWuNnzoQ/Zj70FYjIGhbRvWKnFhsiS56EgdM6mlo2BXn3RLLCYSNHS4+8cOG6wV09le/Wdc01DExMJo9PeqJU4jru5MONngFmPgTVTMeARUa1SfR4BQ363vT8yKjQWbozu446QvwmRmVO16cPP+I6nc8IdIu+Wp8Igix/FNNLPNxv+NPDz2jeTmN2nStFFcMy8GyC3HwHABd5K3HG7D/7HtesOL8E66B5zfL7cz72gLiuAmTlcrs/JDLnfysewzI4N84AFMwjMDTB7NOGBfjabJhrL4BtbUQTy1OjR5vpommOyi6XX7nCIdRL7gFqZ9Zd5Bch8jiS/wVKRk7ZQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=/NhZ5wJy1LRqxbpyNv5WxkQxP9cGKNEzDf6JbFacEV8=; b=P5J/KCJRBmjSozqxPbgpbxDv1UgV0fN5CQKwhjvHVTpdzKiCAbEG530g+J+H33TwsF9rrdKCVpXEwZ5rkohRFS+y15Dxr1T5sQiZNGOkaN1yig+nKwYrAA+2CkrzrNgypuXBzefWtcRi7RX7s97sUstbr1cGV9Rqv5QfTp5t+KK3g3JCmK4c4j3fMsp8Z2qYpR+76CZkkghgclOl2F5Ydh+gn11o3hP4OeNgTgsU9dU24MVi14cLV++EUz1c+k7EZKwNggy6gCswHXJQfypeLZzk28e417xOQIqMhaOLfutU1J6U7SL8j9dWm8yWE9wOdbLOofA9VOAKHcy6O5jRiw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=/NhZ5wJy1LRqxbpyNv5WxkQxP9cGKNEzDf6JbFacEV8=; b=hvHnznApLEL7DzeUZrnmOBRrTtAF8kzVTNjN4z9PN4n6GaNqVweaR5ZqPVyvhBuekKRmNJ6zy3fszICNLcmAWCjpl5L1mTxb2Vz6fjwNLNbiAzMzrYhClNpawlHhO/ntEKCNWnGnhWGFwXEzZiS5bS+daPjGQwFLSfMyo5WoGNWgRdyAx2zVa31KO3Hi9zT1EJqxF78o5DQqpugRVOgrbvE4Urai1C93U9qjOYAWc/CnrsyFhQ9ri5LjY9ew/JG6mORe/sUx7LFR2708MytFhtpglYWegsCYvid3Ao+3fAQLFOr9Jh+cqMqK+0kWnSqXXG8LlfNARpczfVL8sUko0g== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from BN9PR12MB5179.namprd12.prod.outlook.com (2603:10b6:408:11c::18) by DS2PR12MB9749.namprd12.prod.outlook.com (2603:10b6:8:2b9::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.159.19; Mon, 29 Jun 2026 15:54:58 +0000 Received: from BN9PR12MB5179.namprd12.prod.outlook.com ([fe80::cf08:f59b:d016:c95f]) by BN9PR12MB5179.namprd12.prod.outlook.com ([fe80::cf08:f59b:d016:c95f%4]) with mapi id 15.21.0159.018; Mon, 29 Jun 2026 15:54:58 +0000 Message-ID: <16c7c5d4-d596-4a75-ac97-fb9d2c02c80c@nvidia.com> Date: Mon, 29 Jun 2026 21:24:47 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] CPPC: reduce FFH feedback-counter sampling skew on arm64 To: Pengjie Zhang , catalin.marinas@arm.com, will@kernel.org, rafael@kernel.org, lenb@kernel.org, robert.moore@intel.com, beata.michalska@arm.com, zhenglifeng1@huawei.com, zhanjie9@hisilicon.com, cuiyunhui@bytedance.com Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, acpica-devel@lists.linux.dev, linuxarm@huawei.com, jonathan.cameron@huawei.com, prime.zeng@hisilicon.com, wanghuiqiang@huawei.com, xuwei5@huawei.com, lihuisong@huawei.com, yubowen8@huawei.com, wangzhi12@huawei.com, "linux-tegra@vger.kernel.org" References: <20260410094145.4132082-1-zhangpengjie2@huawei.com> Content-Language: en-US From: Sumit Gupta In-Reply-To: <20260410094145.4132082-1-zhangpengjie2@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: PN4P287CA0101.INDP287.PROD.OUTLOOK.COM (2603:1096:c01:278::8) To BN9PR12MB5179.namprd12.prod.outlook.com (2603:10b6:408:11c::18) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN9PR12MB5179:EE_|DS2PR12MB9749:EE_ X-MS-Office365-Filtering-Correlation-Id: ec31e494-4d55-4e47-2509-08ded5f6c525 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|7416014|376014|1800799024|366016|921020|18002099003|22082099003|11063799006|56012099006; X-Microsoft-Antispam-Message-Info: qw//+YAnyDskIA8HOKHIq9pYZUlPkh/x6ha/oKP2gxWX24ATMFaWXKIRcgcviRZYp6kZJh1DHdXW0ubCXHmS7QqlurhwHiuekeZxyoXW6eLSHDIyYm/yC2RRXdp4NddxwTsrOUfyiCRjvTlGNu6hsUiHE3C04srYdvW0YSVSXdOEOQuIzcCHlaaKTunkhoL14Cxh6D9NHM0zYml10uhFNnFmbTIlOhbN/FDgL5I1Z2D1xdqGSbT2rahrpH48DCrakVulSsw0vWlX+GQ4IeLcuiTOatproxliv4W8lbisy7L3QRSCBFg7efOS+WH/b+ZN1w4larjPnKfOiqP5x+qQYpSunAWycww8a8VLzbN8Y78lh2MSp7UolwyuZw8tazcuaniOhDZFABUw1ImStY1W6patbCSjubw3UHkElcMc79nHw83HUP8zmtF9eyf2WSgjM9IjrQUPfW+8YLGTCQq04JrBsziCkcKg9x0gZ4ByTjoHxSseGiBIKruOSX0QQITESWxp/Xe2VWG18vMPZr+BRR8p3Y26XwJ+XPVtS9jfUVOGZHV+8WjuV1QW8qRC//AebW04OyL5m2jCFAl9/QnV79rXfUtQKpbEAfEmLhk9zmroo42E11XkM6j0B4cGyiKCwXD/hvsHvnZRlgu3BA4DvrXEvpOHAo0L5VY2F0QLq8HEo4+UVeNPaHTIExEDGYiCEcJokhOze57rDlxYAL5ubg== X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BN9PR12MB5179.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(23010399003)(7416014)(376014)(1800799024)(366016)(921020)(18002099003)(22082099003)(11063799006)(56012099006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?dW9PTyswb3BIdkhISjRxbzFjNWZmS1VkNGxJZEdDK3pCNmJINi9DNklGQXZB?= =?utf-8?B?RnJUKzlGSTlCQitGZll1bVYwWTBJdDFrQy9ibkJTeThrQnY5bER5UVZGaGxB?= =?utf-8?B?bnpJajhIOXBrTnhDOURLUmd2VUdCbzg2V0ovejJaTWdUT0Z2c0pnV1RMSzlS?= =?utf-8?B?bW02NmluMVlTTzJWZ2xLblpleEJpYXZudzZzbTNxRlEyNVUvVmR6Z1NOK3NR?= =?utf-8?B?RHVhU2RIMnhqYm5ZazZhWVMvT2FNMC9LNTdDRGZDWHluczg1WGY3aVpSU2Ju?= =?utf-8?B?eUdtY2VVZ2hCLy85cnd0eExuVjczNUpwOGZpbGN1RnU3THJhV2Z4UU1BV3Nq?= =?utf-8?B?ZjBlYWQwNDlyYit6SHQyS0hwYmVabHMzN2NZRUR1TXFIdmp3T1VFYjdPL0pH?= =?utf-8?B?ME1Mc1VIRTNNRWk1QUVmTHZzQlNWUlU4cmNML1l3a0JINkNlQ0tFWFl3aFlR?= =?utf-8?B?RDNuSWxvSk04Ymtlak1tWEcrUEJIWmZxNi8rVDR5dXlRb0lhd3EwUDZQeEJM?= =?utf-8?B?b0x5Vlc2R3Q3Vm1XSm45WnNRNHdSOUo3NVFGR2tqNDgyT0hrajNrdXhUSkV5?= =?utf-8?B?Q2kxSzNvSDV4K1U0b0NOWmNLc3U2MkswblNpUzZrcU9zRHRCMHV2RXZMSnRD?= =?utf-8?B?amlmU25xWHE4aFlIbDBGOENDZlUwQ3VoZ2JVVzFTV3BEYlJsUDlFay9naCtO?= =?utf-8?B?N29XTEhrMjRvRUY2YVZTTjl1MU5rcHJnZGpnYi95bm5QSmwrT0ZnVjduTzdj?= =?utf-8?B?RHBlMFgwWElDMFpoaWxUTldoV1VpZXV6MS8zMGRCT0JhMUVpbzFxNVdwbzhI?= =?utf-8?B?WkZnejdNcjdmT09LRlNlU2RIa0UyUENHMUQyNmZEemFUcy9LR0FWQkVyS3Av?= =?utf-8?B?NUZ4QWo4WWtGbFBYRWFmRzcrVmJKWUFzbVFZZTNLTWUydkluNndxbUY5by9v?= =?utf-8?B?eDZZdDgzY2RacHo2RE9rZzdrMDkxa1dTc3dhZE5SZmpSK0x2R2FRVVR1cWo1?= =?utf-8?B?M3FaRUc3NXpTRVlEc2J2YlpIMC9XdnFyaXl1K0xwVzhMYzNYc3BDK1RaN3l4?= =?utf-8?B?a2tpdUpXSnFmeHU1cWN2UDJOUGhkQjJnMjRCdzVvdFRaSG43NWZ5YnAzQnBu?= =?utf-8?B?djl6REZyZ2JtLzM0WDkvR2ptQUVQdUF0ZW9uRDJFeVVsSTBBR2dyU3k3Q3d1?= =?utf-8?B?amNvODc0YUVibVVONTZYdFdaZDg1K1RqM3RjTUFreDZNdUFvaGFOQ3JjVElM?= =?utf-8?B?UUY0TDNLTXNydFZsVE1DblBSRS9jNDNKdmR5WXFxUkxBaG5LaVJ0WmtnNlgx?= =?utf-8?B?T2dlSEh6RWU0ZFBUMXFQRjJuNjhzb3RNRG5zNEdsYldONEZCMlFCd0pFbXNJ?= =?utf-8?B?cXBTT1pneWRwVzludXFZTzhCQWo3TVFyc2dTelFhNlR3MU9IYUVLdkgwK0lU?= =?utf-8?B?OGVBWVUyYm9taGRMa0JvVmZ6UWhBL3hFYlo4N0FFUzNIL1VaZDdDTzNmT2Fv?= =?utf-8?B?Y2lSNCtTYjdGQnV1NzFBQmphK285U3J6NGJVcnJwdUJmdWVZRkZVVHVTZ0F5?= =?utf-8?B?TmxYazFHS3p6Q25Wc0JlblVCcWtpbmJQUGxhOVNlQzNjZ2lTUnN3aVAvMlBX?= =?utf-8?B?SGxUbzNZbWlhTUZTcjF1UGJITzFiWGhVdk0xQWdjakJvTmJHSnVuR2JReUtk?= =?utf-8?B?WnZrS3BvSjhVQ3BhTjVEWjdIZmtCN050L0tQZUxJdi9OTTNLdGhHV0VhK0g2?= =?utf-8?B?c3YxaXk2dlNKeUEwVmhYakxROFZNZnNnaTRRbzhsajJaTkFaVHJXTUVjeWR5?= =?utf-8?B?TjE4TjBpbWpOVjBKK2d1WCtUZURPQ3NsWXMzWUhMdE0zbm1wL2VsVHdWMFh3?= =?utf-8?B?WjFHR1RaWHU5OUs0dzFIUyt0MFNHRUtHUXN6RjNMdmpjN2lsZExOSk9EYVla?= =?utf-8?B?blJzRzBOenlzTE9OL212MmdteWJpYTYyTVlzZTExL0hqL2ZwZVFHWHpRT0VS?= =?utf-8?B?bWlWZVA2UEpUd21Gb1dpQVdMb0VzT2NlN01ITGl2VzY1cTZZRVF3YzZmZWhC?= =?utf-8?B?d2JsOWlnZzN4RUlOa0h0UzkwZ3A4M05idEpLWndiREhKY0Q4Z3dMZmp1ZmZC?= =?utf-8?B?ZzlqTzdlaDF1ZWpENldzSFVLdFpzakRWRGJvZEVDZFhZYjNQV3diL0pjSlQ2?= =?utf-8?B?MG5CaXBMK3ZSdHZ6aE9SM3JYVU1DUzhjcTIveUJ5RHZSTzhrUUx4OVdtL1lE?= =?utf-8?B?UmhNdkxscE1nUEVvYndBb2FWb1RpUEpmQm5EVXgwZUtHa25oVWJKMkVkT3Vl?= =?utf-8?Q?op0nYw2XlxcjL7VKP1?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: ec31e494-4d55-4e47-2509-08ded5f6c525 X-MS-Exchange-CrossTenant-AuthSource: BN9PR12MB5179.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Jun 2026 15:54:58.2422 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: K3wz0GisUb2VqLRRR3Qx2S+G/ASzf9bzGWcTdUry0P0QDlQpP8Mmd1/Qwxeq0X806s429Y2SzXWkXQWoiPnGuA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS2PR12MB9749 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260629_085505_769739_EFF38D28 X-CRM114-Status: GOOD ( 14.78 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 10/04/26 15:11, Pengjie Zhang wrote: > External email: Use caution opening links or attachments > > > The legacy CPPC feedback-counter path reads the delivered and reference > performance counters separately. > > On arm64 systems using AMU-backed CPPC FFH counters, each FFH read is > served through a cross-CPU counter read helper. Reading the counters > separately therefore widens the sampling window between them and can > skew the delivered/reference ratio used by cpuinfo_cur_freq. Under heavy > load, the skew is observable as transient values that may exceed the > platform maximum, as discussed in [1] and [2]. > > This series adds a small generic hook for architectures that can obtain > both FFH feedback counters in one operation, while preserving the > existing per-register read path as the fallback. > > Patch 1 adds the generic CPPC hook and uses it from cppc_get_perf_ctrs(). > Patch 2 implements the hook on arm64 by sampling both AMU counters in a > single operation on the target CPU. > > [1] https://lore.kernel.org/all/20231025093847.3740104-4-zengheng4@huawei.com/ > [2] https://lore.kernel.org/all/20231212072617.14756-1-lihuisong@huawei.com/ > > Signed-off-by: Pengjie Zhang > > Pengjie Zhang (2): > ACPI: CPPC: add paired FFH feedback-counter read hook > arm64: topology: read CPPC FFH feedback counters in one operation > > arch/arm64/kernel/topology.c | 75 ++++++++++++++++++++++++++++++++---- > drivers/acpi/cppc_acpi.c | 58 +++++++++++++++++++++++++--- > include/acpi/cppc_acpi.h | 7 ++++ > 3 files changed, 127 insertions(+), 13 deletions(-) > > -- Hi Pengjie, Thanks for the patches. The series looks good to me, and it fixes the cpuinfo_cur_freq spikes on an NVIDIA Vera (FFH) platform. Just one nit on patch 2 (counter read order), noted there. Tested-by: Sumit Gupta Reviewed-by: Sumit Gupta Thanks, Sumit