From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF38BC64EC4 for ; Fri, 3 Mar 2023 23:29:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229643AbjCCX3D (ORCPT ); Fri, 3 Mar 2023 18:29:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229642AbjCCX3C (ORCPT ); Fri, 3 Mar 2023 18:29:02 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 154043A851 for ; Fri, 3 Mar 2023 15:29:00 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C84D6B81928 for ; Fri, 3 Mar 2023 23:28:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE3C1C4339B; Fri, 3 Mar 2023 23:28:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677886137; bh=Mc/i4nO3OoOhgYlqRTsI8DqVkrOnmuiXyLo29wHohNc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=AEVoUEvdxtj/yv4Ah2V/jMesawEKZxYqvJKCyJ1JvZ4K0ShtO0EXpUQVEmYj6nTA9 GHCci278ugwI8RiMyJy2WAciI0GK+THNUPMKmILZIsjtu3Cna597BTzIC91+cCyHSM KzA7cSVAvAJ37pj3RfhuY8CJ5+hP6l7RU6t5XkqAY4IhroeQkWpIr5LXkP5ckoD9KG EfQ5aaLqjyU/z/tEVnROZX5eQbUyxF73SU3fizk71Nrjf7wrANvPTgztunEbVQU8LF wETriSDpJMFmq59o5KQ0on1GJi519qXPnQnnND7sX1X/7Wdk+36sayPDDvwL03U/+m zMWZ3knf/un/Q== Date: Fri, 3 Mar 2023 15:28:55 -0800 From: Jakub Kicinski To: =?UTF-8?B?S8O2cnk=?= Maincent Cc: "Russell King (Oracle)" , Richard Cochran , andrew@lunn.ch, davem@davemloft.net, f.fainelli@gmail.com, hkallweit1@gmail.com, netdev@vger.kernel.org, Thomas Petazzoni , Maxime Chevallier Subject: Re: [PATCH RFC net-next] net: phy: add Marvell PHY PTP support [multicast/DSA issues] Message-ID: <20230303152855.23588b39@kernel.org> In-Reply-To: <20230303141247.4acd6863@kmaincent-XPS-13-7390> References: <20230228141630.64d5ef63@kmaincent-XPS-13-7390> <20230228142648.408f26c4@kernel.org> <20230228145911.2df60a9f@kernel.org> <20230301170408.0cc0519d@kmaincent-XPS-13-7390> <20230302084932.4e242f71@kernel.org> <20230302180616.7bcfc1ef@kmaincent-XPS-13-7390> <20230302092320.6ee8eb6d@kernel.org> <20230303141247.4acd6863@kmaincent-XPS-13-7390> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, 3 Mar 2023 14:12:47 +0100 K=C3=B6ry Maincent wrote: > > Do you happen to have a datasheet for MACB? The time stamping > > capability is suspiciously saved in a variable called hw_dma_cap > > which may indicate it's a DMA time stamp not a true PTP stamp. > >=20 > > Quite a few NICs/MACs support DMA time stamps because it's far=20 > > easier to take the stamp where the descriptor writing logic is > > (DMA block) than take it at the end of the MAC and haul it all=20 > > the way thru the pipeline back to the DMA block. =20 >=20 > I don't have the datasheet but indeed you seem to have right. From the su= pport > commit message:=20 > > Time stamps are obtained from the dma buffer descriptors =20 That's just saying that the time stamp is communicated via=20 a descriptor rather than a register, so not a strong proof=20 of where it's taken. > I suppose it is less precise as using true PTP stamp as it is an hardware= block > further. Is that right?