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Wed, 3 Sep 2025 15:11:42 +0000 Received: from AM8PR04MB7779.eurprd04.prod.outlook.com ([fe80::7417:d17f:8d97:44d2]) by AM8PR04MB7779.eurprd04.prod.outlook.com ([fe80::7417:d17f:8d97:44d2%7]) with mapi id 15.20.9094.015; Wed, 3 Sep 2025 15:11:41 +0000 Date: Wed, 3 Sep 2025 18:11:38 +0300 From: Vladimir Oltean To: Richard Cochran Cc: Wei Fang , andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, xiaoning.wang@nxp.com, Frank.Li@nxp.com, yangbo.lu@nxp.com, christophe.leroy@csgroup.eu, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, imx@lists.linux.dev Subject: Re: [PATCH net-next 0/3] ptp: add pulse signal loopback support for debugging Message-ID: <20250903151138.malmfj53hew7caze@skbuf> References: <20250903083749.1388583-1-wei.fang@nxp.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: VI1PR04CA0075.eurprd04.prod.outlook.com (2603:10a6:802:2::46) To AM8PR04MB7779.eurprd04.prod.outlook.com (2603:10a6:20b:24b::14) X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: AM8PR04MB7779:EE_|AS8PR04MB8466:EE_ X-MS-Office365-Filtering-Correlation-Id: ada65c1b-41d0-4c81-51ed-08ddeafc3022 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|19092799006|7416014|376014|10070799003|1800799024; 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The commit message of patch 2/3 shows that you can record extts events for the periodic output signal emitted by the device, without this signal ever being required to be routed in any particular way on the PCB, through the SoC's pins. So you can make sure that the pulse intervals and their phase alignment are correct from the perspective of the emitting PHC's time base. Or you can use it as a built-in extts event generator when you have no external equipment which does that, as I did a few years ago to validate the extts functionality on ptp_qoriq. > It seems pointless to me... Well, it's pointless in the same sense that a mirror is pointless.