From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [78.32.30.218]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 09A5426BD95 for ; Fri, 28 Feb 2025 14:38:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=78.32.30.218 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740753509; cv=none; b=nLbyOWkPyJZ4YkXoKDAs+zgTLFvROkQWdK0la5IGlRSTnU9z07x37p9vh/JN+0O3dmp4RnVBdhjLnmRHiKxPkX/OTIEEqY750oCV87KcBh17M0/G6XFiYg5rVOC4F9UjhGNHTE6Cyqy7MBjusWKcO484PmO3ZKr7R8LGghsKR7g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740753509; c=relaxed/simple; bh=VFV4V+KaAVrirb4p3PgEObarCo2A/dHguaMyEXLgNKE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ciQQknwbI8DP9Caw4YJx6k/HeiK3JsEvvgK+k8b7P5OQgnROHi7ctaDYyJCzFXRLBeBhXMg6/C5c0AawJX5DK6byiT2xgA6r97qucv0mjCOdVrnVE88Uy5GWv1PyP8idfjIBBbGOhRGgljZGAjaYG5KFlnLPG/1W0XiKeQZxu2I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk; spf=none smtp.mailfrom=armlinux.org.uk; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b=iFtcGjYq; arc=none smtp.client-ip=78.32.30.218 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="iFtcGjYq" 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=3tXnve9p7OqPOELNgMc2EsgP+Zfm3xXu92ERqG5r7f4=; b=iFtcGjYqiy3IOCZDaithdJHkh4 CU+JJwQVo5k7U4sa3fUv8ige18h8zr+4GdMraoHFGWeOf4zC+u0c/rC+w6HK0gP49RT7j0ZhNXdYg Xo0KXs9QxxcaNvZTTX9c09YPKLWKeegsJ7GPzyGiAHfN+evABjifq7qMKSvG4BvNKB80RdVvgcklS XvpK8Y3ZuS4oSi0ailoVgdn2R2bUyWK3YCkr4INHGO+1wYFhQHxMt/f694g/CGw/Et7wAHt15uHPz K+TSiPZlvmG36cQbvbMTkzQXYQkABeFoOITqOMqdJnWJP9MQeYJ9o/vzo79Fuz01tErck8kn4uUTE ZDLZ2BvQ==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:40904) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1to1VK-00027b-2s; Fri, 28 Feb 2025 14:38:18 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.96) (envelope-from ) id 1to1VH-0000oR-2d; Fri, 28 Feb 2025 14:38:15 +0000 Date: Fri, 28 Feb 2025 14:38:15 +0000 From: "Russell King (Oracle)" To: Andrew Lunn Cc: Furong Xu <0x1207@gmail.com>, Heiner Kallweit , Alexandre Torgue , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Jon Hunter , linux-arm-kernel@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, Maxime Coquelin , netdev@vger.kernel.org, Paolo Abeni , Thierry Reding Subject: Re: [PATCH RFC net-next 1/5] net: stmmac: call phylink_start() and phylink_stop() in XDP functions Message-ID: References: <20250228153122.00007c75@gmail.com> <7706823a-a787-4c7e-a6ac-9a4feaf76dee@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: <7706823a-a787-4c7e-a6ac-9a4feaf76dee@lunn.ch> Sender: Russell King (Oracle) On Fri, Feb 28, 2025 at 02:14:29PM +0100, Andrew Lunn wrote: > On Fri, Feb 28, 2025 at 03:31:22PM +0800, Furong Xu wrote: > > On Thu, 27 Feb 2025 15:05:02 +0000 > > "Russell King (Oracle)" wrote: > > > > > Phylink does not permit drivers to mess with the netif carrier, as > > > this will de-synchronise phylink with the MAC driver. Moreover, > > > setting and clearing the TE and RE bits via stmmac_mac_set() in this > > > path is also wrong as the link may not be up. > > > > > > Replace the netif_carrier_on(), netif_carrier_off() and > > > stmmac_mac_set() calls with the appropriate phylink_start() and > > > phylink_stop() calls, thereby allowing phylink to manage the netif > > > carrier and TE/RE bits through the .mac_link_up() and .mac_link_down() > > > methods. > > > > > > Note that RE should only be set after the DMA is ready to avoid the > > > receive FIFO between the MAC and DMA blocks overflowing, so > > > phylink_start() needs to be placed after DMA has been started. > > > > > > Signed-off-by: Russell King (Oracle) > > > XDP programs work like a charm both before and after this patch. > > > > Tested-by: Furong Xu <0x1207@gmail.com> > > Thanks for testing this. > > Could you give a little details of how you actually tested it? > > The issues here is, when is the link set admin up, requiring that > phylink triggers an autoneg etc. > > For plain old TCP/IP, you at some point use: > > ip link set eth42 up > > which will cause the core to call the drivers open() method, which > then triggers phylnk. > > The carrier manipulation which this code replaces seems to suggest you > can load an XDP program while the interface is admin down, and that > action of loading the program will implicitly set the carrier up. It won't. See drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c::stmmac_xdp_set_prog(): if_running = netif_running(dev); need_update = !!priv->xdp_prog != !!prog; if (if_running && need_update) stmmac_xdp_release(dev); ... if (if_running && need_update) stmmac_xdp_open(dev); stmmac_xdp_open() and stmmac_xdp_release() will only be called if netif_running() returns true as explained yesterday (but maybe without enough detail). This tests __LINK_STATE_START in dev->state, which is set just before calling .ndo_open(), and cleared if it fails or before calling .ndo_stop(). Thus, netif_running() indicates whether the net core thinks the device is adminsitratively "up". Therefore, in the old code, if the programme is changed while the device is administratively down, netif_running() will return false, if_running will be false, and neither stmmac_xdp_release() nor stmmac_xdp_open() will be called. Hope that addresses your concern. Thanks. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!