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Wed, 7 Feb 2024 06:10:10 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6600,9927,10976"; a="436054107" X-IronPort-AV: E=Sophos;i="6.05,250,1701158400"; d="scan'208";a="436054107" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Feb 2024 22:10:09 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,250,1701158400"; d="scan'208";a="5849933" Received: from inlubt0316.iind.intel.com ([10.191.20.213]) by fmviesa004.fm.intel.com with ESMTP; 06 Feb 2024 22:10:03 -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 Date: Wed, 7 Feb 2024 11:38:53 +0530 Message-Id: <20240207060854.6524-11-lakshmi.sowjanya.d@intel.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20240207060854.6524-1-lakshmi.sowjanya.d@intel.com> References: <20240207060854.6524-1-lakshmi.sowjanya.d@intel.com> MIME-Version: 1.0 X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1707286210; x=1738822210; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=6PS4+2Ywv1DMIM5u9+tNfbsYVKa0PISW1H4pAS3IZH0=; b=hNBTfKVHiOQvJvGJmtLGzCRM+Z7ooOQVcC8L6+4jyuvlCKrPXAFpyDmD 7kLT032VSW9S+pZ8mPBBVkH7/Uot52VmmottkKGSHMHSzcH7QWH7gsJuD YXskFrgWrf+1OnrPL68iuRRa4aiYbwcbZArqGAEAkvRamGcGRGHWDGkuk rIZipmyKLLC2XHpFhrIHBUrw5SeCYHJfff2hnhZcxd5b3i+JLFKt+Eb+u X04ve7zoOU5Q6609wTCb0ZI7MF7u6gzvNdsvdTH/IQCZbBWTPPHyXOjsP zxeAkd5qekINTytSFBe9cl0g30ZJV1ymK6gBJFziAPiTemH7W8Wm866eP g==; X-Mailman-Original-Authentication-Results: smtp4.osuosl.org; dmarc=pass (p=none dis=none) header.from=intel.com X-Mailman-Original-Authentication-Results: smtp4.osuosl.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=hNBTfKVH Subject: [Intel-wired-lan] [PATCH v4 10/11] Documentation: driver-api: pps: Add Intel Timed I/O PPS generator X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: christopher.s.hall@intel.com, subramanian.mohan@intel.com, lakshmi.sowjanya.d@intel.com, linux-doc@vger.kernel.org, netdev@vger.kernel.org, pandith.n@intel.com, x86@kernel.org, eddie.dong@intel.com, jesse.brandeburg@intel.com, linux-sound@vger.kernel.org, alexandre.torgue@foss.st.com, peter.hilber@opensynergy.com, mallikarjunappa.sangannavar@intel.com, joabreu@synopsys.com, intel-wired-lan@lists.osuosl.org, mcoquelin.stm32@gmail.com, thejesh.reddy.t.r@intel.com, perex@perex.cz, anthony.l.nguyen@intel.com, andriy.shevchenko@linux.intel.com, davem@davemloft.net Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" 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..52a6d5faf885 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 signals. + +Timed I/O and system time are both driven by same hardware clock. The signal +is 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 the 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