From patchwork Mon Mar 17 13:55:40 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Artem Bityutskiy X-Patchwork-Id: 874266 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.14]) (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 7C06323ED62 for ; Mon, 17 Mar 2025 13:55:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.14 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742219748; cv=none; b=q0xgr7jlDzZatZceJBLQoGytjciiDLJrtv7j8Br4mjkrP9EjxtpQIjbc1JgJ6FbbTK7dM4HvDhLL49rSGJATPLbQF7PudlSDGq1fcoxDlpozygqP1XV/LC0ZXQAYlSOiYf88UDExVsNRfcPK/cFsz5cWOkfLKAzoP43+vy7Xd/Q= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742219748; c=relaxed/simple; bh=u9vODP8v8WgPk/9sAW1h8ebtIALXZ7YfXOpE32DjU80=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=E5+dvvF8J36yLiysxdy4xH6VikkzffDciDGEjvl3+uGBNua4Iiz7gG4vOtpZX4iQ36dGzA4nRx1W8ccursEf0CTF6VSl3udNKd9WSEZlkPzJhvVCApEDvXzT4L04o7HbWmHFYA6EiB2gGzXlFqD/EU/EtCUeSGVsxhjhMHkbddU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com; spf=fail smtp.mailfrom=gmail.com; arc=none smtp.client-ip=192.198.163.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=gmail.com X-CSE-ConnectionGUID: JXN1PUbLQ1ewTyqqnqUiXg== X-CSE-MsgGUID: uT4KdloFQ1+zAeuTe4rBkQ== X-IronPort-AV: E=McAfee;i="6700,10204,11376"; a="43515490" X-IronPort-AV: E=Sophos;i="6.14,254,1736841600"; d="scan'208";a="43515490" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2025 06:55:46 -0700 X-CSE-ConnectionGUID: W3uA1tPIRGKQ2iE9/hVKng== X-CSE-MsgGUID: RnibvvxzQFS0xx4YbtRNiQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.14,254,1736841600"; d="scan'208";a="127115532" Received: from powerlab.fi.intel.com (HELO powerlab.backendnet) ([10.237.71.25]) by orviesa005.jf.intel.com with ESMTP; 17 Mar 2025 06:55:45 -0700 From: Artem Bityutskiy To: "Rafael J. Wysocki" Cc: Linux PM Mailing List Subject: [PATCH v3 2/3] Documentation: admin-guide: pm: Document intel_idle C1 demotion Date: Mon, 17 Mar 2025 15:55:40 +0200 Message-ID: <20250317135541.1471754-3-dedekind1@gmail.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250317135541.1471754-1-dedekind1@gmail.com> References: <20250317135541.1471754-1-dedekind1@gmail.com> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Artem Bityutskiy Document the intel_idle driver sysfs file for enabling/disabling C1 demotion. Signed-off-by: Artem Bityutskiy --- Documentation/admin-guide/pm/intel_idle.rst | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/Documentation/admin-guide/pm/intel_idle.rst b/Documentation/admin-guide/pm/intel_idle.rst index 5940528146eb0..ed6f055d4b148 100644 --- a/Documentation/admin-guide/pm/intel_idle.rst +++ b/Documentation/admin-guide/pm/intel_idle.rst @@ -38,6 +38,27 @@ instruction at all. only way to pass early-configuration-time parameters to it is via the kernel command line. +Sysfs Interface +=============== + +The ``intel_idle`` driver exposes the following ``sysfs`` attributes in +``/sys/devices/system/cpu/cpuidle/``: + +``intel_c1_demotion`` + Enable or disable C1 demotion for all CPUs in the system. This file is + only exposed on platforms that support the C1 demotion feature and where + it was tested. Value 0 means that C1 demotion is disabled, value 1 means + that it is enabled. Write 0 or 1 to disable or enable C1 demotion for + all CPUs. + + The C1 demotion feature involves the platform firmware demoting deep + C-state requests from the OS (e.g., C6 requests) to C1. The idea is that + firmware monitors CPU wake-up rate, and if it is higher than a + platform-specific threshold, the firmware demotes deep C-state requests + to C1. For example, Linux requests C6, but firmware noticed too many + wake-ups per second, and it keeps the CPU in C1. When the CPU stays in + C1 long enough, the platform promotes it back to C6. This may improve + some workloads' performance, but it may also increase power consumption. .. _intel-idle-enumeration-of-states: