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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Maxime Coquelin , Alexandre Torgue , netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-tegra@vger.kernel.org, Alexis Lothorrr References: <20250612062032.293275-1-jonathanh@nvidia.com> <85e27a26-b115-49aa-8e23-963bff11f3f6@lunn.ch> <353f4fd1-5081-48f4-84fd-ff58f2ba1698@lunn.ch> <9544a718-1c1a-4c6b-96ae-d777400305a7@nvidia.com> <5a3e1026-740a-4829-bfd2-ce4c4525d2a0@lunn.ch> <4861a4cb-d653-4c5d-8d96-c7acac501004@lunn.ch> From: Jon Hunter Content-Language: en-US In-Reply-To: <4861a4cb-d653-4c5d-8d96-c7acac501004@lunn.ch> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: LO4P265CA0254.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:37c::18) To PH0PR12MB8773.namprd12.prod.outlook.com (2603:10b6:510:28d::18) Precedence: bulk X-Mailing-List: linux-tegra@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH0PR12MB8773:EE_|MN0PR12MB5763:EE_ X-MS-Office365-Filtering-Correlation-Id: d9159ef8-6123-4605-f743-08ddb48ebb45 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014; 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How are >>> they working? Must it be the fallback? The ptp-ref clock is actually >>> turned on, and if the ptp-ref clock and the main clock tick at the >>> same rate, ptp would work. I _guess_, if the main clock and the >>> ptp-ref clock tick at different rates, you get something from the ptp >>> hardware, but it probably does not get sync with a grand master, or if >>> it does, the jitter is high etc. So in effect it is still broken. >>> >>> Can somebody with the datasheet actually determine where ptp-ref clock >>> comes from? Is it just a gated main clock? Is it from a pin? >> >> Looking at the datasheet, this is a pin to the controller and sourced from >> an external clock. > > So the fallback of the main clock is not likely to help, unless by > chance the external clock and the main clock happen to be the same > frequency. Actually the fallback to the main clock is not applicable here for this Tegra device because we don't have a clock called 'stmmaceth'. In fact, that is something else we should fix because for Tegra234, I see ... tegra-mgbe 6800000.ethernet: Cannot get CSR clock However, this is expected because there is no 'stmmaceth'. The fallback to the main clock is only applicable to !snps,dwc-qos-ethernet-4.10 devices but this should also be applicable to 'nvidia,tegra234-mgbe' as well. >> AFAIK we have never tested PTP with this driver on this device. So the risk >> of breaking something is low for this device. > > So it seems like the simple fix is to list both ptp-ref and ptp_ref, > pointing to the same clock, along with a comment explaining why you > have this odd construction. > > Please could you test that? I am sure it will work and yes I can test. I am a bit concerned that the device-tree maintainers will not want this because strictly device-tree should describe the hardware and adding workarounds is not ideal. Don't get me wrong this is a massive oversight on our behalf to begin with. Ideally we would handle this somewhere in the dwmac-tegra.c driver. Jon -- nvpublic