From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="wv7i7KIs" Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 44C21E3; Mon, 20 Nov 2023 11:10:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=nQggdxI9MQ2FS/W0GEG8D1cdBawPg8AZAzpNVf/hhDE=; b=wv7i7KIsLK5sNs6GxBZ1eTPvBs 8D8waGZ6Bwkk1VOH7PyCYlBdY9FsgioEi1s1ihGrbcNKiF9AfI7TAtw9C3PUA/kTAIHd12QNvdw4o DOtwmu10YB8J+ElXm/wS/syMFmzPx6OXbkbgALZ95FKgsPgKIEkAwVFlO2KcY8A133LpHG23/UDXt DxGwZ0Ee1yOjGDnINBC/yfQAQU9K0KOT2AdYYXMPnLAMhzilCsGlSHatd15UG/R4Zf831IuuTQvtR o6JmuUipByC7p2R4IlIWia1+wi6WZUEDC0JRDZ+tVZBruY6fC5yfCeWJPrdORF0W9FOWHPCbxrmm4 v6qFC6bA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:60598) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1r59ef-00062L-1c; Mon, 20 Nov 2023 19:09:57 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1r59ed-0003Q4-V6; Mon, 20 Nov 2023 19:09:55 +0000 Date: Mon, 20 Nov 2023 19:09:55 +0000 From: "Russell King (Oracle)" To: Andrew Lunn Cc: Jakub Kicinski , Vladimir Oltean , =?iso-8859-1?Q?K=F6ry?= Maincent , Florian Fainelli , Broadcom internal kernel review list , Heiner Kallweit , "David S. Miller" , Eric Dumazet , Paolo Abeni , Richard Cochran , Radu Pirea , Jay Vosburgh , Andy Gospodarek , Nicolas Ferre , Claudiu Beznea , Willem de Bruijn , Jonathan Corbet , Horatiu Vultur , UNGLinuxDriver@microchip.com, Simon Horman , Thomas Petazzoni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Maxime Chevallier Subject: Re: [PATCH net-next v7 15/16] net: ethtool: ts: Let the active time stamping layer be selectable Message-ID: References: <20231114-feature_ptp_netnext-v7-15-472e77951e40@bootlin.com> <20231118183433.30ca1d1a@kernel.org> <20231120104439.15bfdd09@kmaincent-XPS-13-7390> <20231120105255.cgbart5amkg4efaz@skbuf> <20231120121440.3274d44c@kmaincent-XPS-13-7390> <20231120120601.ondrhbkqpnaozl2q@skbuf> <20231120144929.3375317e@kmaincent-XPS-13-7390> <20231120142316.d2emoaqeej2pg4s3@skbuf> <20231120093723.4d88fb2a@kernel.org> <157c68b0-687e-4333-9d59-fad3f5032345@lunn.ch> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <157c68b0-687e-4333-9d59-fad3f5032345@lunn.ch> Sender: Russell King (Oracle) On Mon, Nov 20, 2023 at 07:39:35PM +0100, Andrew Lunn wrote: > > What about my use case of having a NIC which can stamp at a low rate > > at the PHY (for PTP) and high rate at the DMA block (for congestion > > control)? Both stamp points have the same PHC index. > > How theoretical is that? To me, it seems more likely you have two PHC. > > The PHY stamping tends to be slow because of the MDIO bus. If the MAC > has fast access to the PHC, it means its not on the MDIO bus. It > probably means you have the PHY integrated into the MAC/SoC, so the > MAC can access it. But if its integrated like this, i don't see why > PHY stamping should be particularly slow. So you can probably use it > for congestion control. And then you don't need DMA stamping. > > Do you know of real hardware with a MAC and a PHY sharing a PHC? Not so much a MAC and PHY sharing a PHC, but I notice in USXGMII-M, there is the ability for the PHY to pass the timestamp back to the MAC through the USXGMII-M connection - which would eliminate the problems of accessing the PHY to get that the timestamps. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!