From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from vps0.lunn.ch (vps0.lunn.ch [156.67.10.101]) (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 AF3311E1DFC; Wed, 23 Jul 2025 14:28:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=156.67.10.101 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753280920; cv=none; b=bgFxBtJvkIG0KainXRwhWcsc8kBKMJY59QCrIKYtubcpq80VUMYdSQCkUpKpeD+PIZS3xGLLNrMEQDP2tG8gxfNclWV0qy1XtibvSEfZJIIYhvjiNJFUPRekQqzqaSN/YIHpKs4tCs7vCm/xW+4+qoBHeWYiyKfFHH3Fk1Ra1aM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753280920; c=relaxed/simple; bh=Bb/XIIaBN/0UhJhFGasC1pbKYzuf1LGwlcF6he+lC4s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rsjMXyxikpK4vZqwHLYVSlsEa43/FCnK9fQE+Bh8dYa4RjRRCOl5hX/n/JzE1pPL0Wt9FKEjToud7YwR24/umudvN7OtGW8/Lr2zgaoyckBzLqOC2SB8Hc2ESJNLQB8qG9xVqDr6738tYFr3dJ4G4Z6cBLuYGqQrobOyBTCxsms= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lunn.ch; spf=pass smtp.mailfrom=lunn.ch; dkim=pass (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b=Au4h0cym; arc=none smtp.client-ip=156.67.10.101 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lunn.ch Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lunn.ch Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b="Au4h0cym" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Disposition:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:From:Sender:Reply-To:Subject: Date:Message-ID:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:Content-Disposition:In-Reply-To:References; bh=NfOvOHP63AILH7Fg86c4DTpSZG2INn5g2Y9EbzDcQfI=; b=Au4h0cymEHwbvqdy1U5OzLXKP8 lxekCJGo9MDcb4q1YihKBjPs1gnbSa8Ahr8C6RCbErZ9NbPBXj7kIZvCony+YAjf1TdaZhYEfdex/ Az5Bb9zcjUfNVrH/i10CutlMqVZIZGAepCijdWaxMz0MdlRxqHuLmxQOJX0F5lXyz6NU=; Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2) (envelope-from ) id 1ueaSL-002bFe-Ec; Wed, 23 Jul 2025 16:28:29 +0200 Date: Wed, 23 Jul 2025 16:28:29 +0200 From: Andrew Lunn To: Oleksij Rempel Cc: Horatiu Vultur , hkallweit1@gmail.com, linux@armlinux.org.uk, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] net: phy: micrel: Add support for lan8842 Message-ID: References: <20250721071405.1859491-1-horatiu.vultur@microchip.com> <20250723090145.o2kq4vxcjrih54rt@DEN-DL-M31836.microchip.com> Precedence: bulk X-Mailing-List: linux-kernel@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: > # FLF Behavior (Immediate Failure) > An FLF-enabled PHY is designed to report link instability almost > immediately (~1 ms). Instead of trying to recover silently, it > immediately reports a hard link failure to the operating system. > > # The Disadvantage in a Single-Link System > > For a system with only one link, this "fail-fast" approach can be a > disadvantage. Consider a short, recoverable noise burst: > > - Without FLF: The PHY uses its 750 ms grace period to recover. The > link stays up, and the service interruption is limited to brief packet > loss. > > - With FLF: The PHY reports "link down" after ~1 ms. The operating > system tears down the network interface. Even if the hardware recovers > quickly, the OS has to bring the interface back up, re-run DHCP, and > re-establish all application connections. This system-level recovery > often takes much longer than the original glitch. > > In short, FLF can turn a minor, recoverable physical-layer glitch into a > more disruptive, longer-lasting outage at the application level when > there is no backup link to switch to. Fast link down can be a useful feature to have, but the PHY should default to what 802.3 says. There is however: ETHTOOL_PHY_FAST_LINK_DOWN which two drivers support. Andrew