From patchwork Thu Dec 21 09:32:53 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "D, Lakshmi Sowjanya" X-Patchwork-Id: 13501515 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.12]) (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 2630F5277C; Thu, 21 Dec 2023 09:34:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="MmWFtQVx" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1703151242; x=1734687242; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=M7wCBVGLoY9FqwR8B4e75uBEBjNx5OX2ShepOLnPD5U=; b=MmWFtQVxbAlz9EeNt1645rwfOSoyjnFQmTlfGqS3tJQlU6n/8SGLgn6Z BRE8ddphkC0vNa+NZj9SCHSXwAl9bUp9imVKld1QohZ1Gt82WbkO+W1f2 FOxMZ1egW6oOOcQ3M8mDx9H7pOPBWkZAqMPvqdL9hjITAWglCabbGK+id QL+uX2MkwymU4wL3MelUNrtB/D7t6wdQ5wGVpJt2nbNnqCeqzINxeN7Z5 fGtgYrZi5CHIuQIUVCaDRqh8U7yPFhHJGw0STZfKMx5fEVLfYRF6RiinI jn6KzuvHcjTYgyZBJqHI2OOd4Zj91m3LZmy6ObfVh4vADCtT/WzH5+vSM g==; X-IronPort-AV: E=McAfee;i="6600,9927,10930"; a="3188668" X-IronPort-AV: E=Sophos;i="6.04,293,1695711600"; d="scan'208";a="3188668" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Dec 2023 01:34:00 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10930"; a="810918264" X-IronPort-AV: E=Sophos;i="6.04,293,1695711600"; d="scan'208";a="810918264" Received: from inlubt0316.iind.intel.com ([10.191.20.213]) by orsmga001.jf.intel.com with ESMTP; 21 Dec 2023 01:33:53 -0800 From: lakshmi.sowjanya.d@intel.com To: tglx@linutronix.de, jstultz@google.com, giometti@enneenne.com, corbet@lwn.net, linux-kernel@vger.kernel.org Cc: x86@kernel.org, netdev@vger.kernel.org, linux-doc@vger.kernel.org, intel-wired-lan@lists.osuosl.org, andriy.shevchenko@linux.intel.com, eddie.dong@intel.com, christopher.s.hall@intel.com, jesse.brandeburg@intel.com, davem@davemloft.net, alexandre.torgue@foss.st.com, joabreu@synopsys.com, mcoquelin.stm32@gmail.com, perex@perex.cz, linux-sound@vger.kernel.org, anthony.l.nguyen@intel.com, pandith.n@intel.com, mallikarjunappa.sangannavar@intel.com, thejesh.reddy.t.r@intel.com, lakshmi.sowjanya.d@intel.com Subject: [RFC PATCH v2 09/10] Documentation: driver-api: pps: Add Intel Timed I/O PPS generator Date: Thu, 21 Dec 2023 15:02:53 +0530 Message-Id: <20231221093254.9599-10-lakshmi.sowjanya.d@intel.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20231221093254.9599-1-lakshmi.sowjanya.d@intel.com> References: <20231221093254.9599-1-lakshmi.sowjanya.d@intel.com> Precedence: bulk X-Mailing-List: linux-sound@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-State: RFC From: Lakshmi Sowjanya D Add Intel Timed I/O PPS usage instructions. Co-developed-by: Pandith N Signed-off-by: Pandith N Signed-off-by: Lakshmi Sowjanya D Reviewed-by: Andy Shevchenko --- Documentation/driver-api/pps.rst | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/Documentation/driver-api/pps.rst b/Documentation/driver-api/pps.rst index 78dded03e5d8..cb1e4d814d37 100644 --- a/Documentation/driver-api/pps.rst +++ b/Documentation/driver-api/pps.rst @@ -246,3 +246,25 @@ delay between assert and clear edge as small as possible to reduce system latencies. But if it is too small slave won't be able to capture clear edge transition. The default of 30us should be good enough in most situations. The delay can be selected using 'delay' pps_gen_parport module parameter. + + +Intel Timed I/O PPS signal generator +------------------------------------ + +Intel Timed I/O is a high precision device, present on 2019 and newer Intel +CPUs, that can generate PPS signal. + +Timed I/O and system time are both driven by same hardware clock, The signal +generated with a precision of ~20 nanoseconds. The generated PPS signal +is used to synchronize an external device with system clock. For example, +Share your clock with a device that receives PPS signal, generated by +Timed I/O device. There are dedicated Timed I/O pins to deliver PPS signal +to an external device. + +Usage of Intel Timed I/O as PPS generator: + +Start generating PPS signal:: + $echo 1 > /sys/devices/platform/INTCxxxx\:00/enable + +Stop generating PPS signal:: + $echo 0 > /sys/devices/platform/INTCxxxx\:00/enable