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 9EDA23B7B61; Thu, 16 Apr 2026 12:25:46 +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=1776342348; cv=none; b=MCbHc4gkhgIydlXztVGP3VE0gMEgp9bTgJ7T0ljW1v6NtUgmw+ce1YvXwTXnI0q5PJuoUqX10kKoABHlF+6go+VfTAGC1eCzJNrvxxngwQet3A1+7AUqdtiSHIVT+ivak43hAL5pEivh9JjkKWqLoEFStYelI6rA6CfWH61Tiqw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776342348; c=relaxed/simple; bh=o6GLJgpl3wqGe0icq+9A06A6j6sCyGCrvbXWN1isA8U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=t0LTBdzXLoClh3efVUqd6+Zjac5oN592kwYT6scuGny8Qan5gYml2uuudxy/07+1aTBXwd52TCXAttKfr/EKvVUpnVYADHa9W0bLLoqHx5VFJT+czJH8RMH/qymFLTk/HuanFyXUsXMHvCwQnB8yIGbr76YPHKam7OP3oUzeJC0= 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=TFn8laKe; 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="TFn8laKe" 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=a+ibqk4w3Rjdz3Ip4cq3cGoMzx070Y2r4edXmCZUgls=; b=TFn8laKeThTAjsxhp2wbxOCjGq WdvQRtXiBHPT6ODzvsfvmctpBVv3w6o9FlCwKZQItDfyXUFjwtc6oPJm5wywPw4+tEUXRa7Ex69KF 8g0olUJOO1WO5OQTlLrN9GXR6Y1Pm9lOJizcKgnY8pzYJfnCyug0C94Voc+Of69U/UtQ=; Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2) (envelope-from ) id 1wDLml-00GHrL-3s; Thu, 16 Apr 2026 14:25:31 +0200 Date: Thu, 16 Apr 2026 14:25:31 +0200 From: Andrew Lunn To: Fidelio LAWSON Cc: Marek Vasut , Woojung Huh , UNGLinuxDriver@microchip.com, Vladimir Oltean , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Maxime Chevallier , Simon Horman , Heiner Kallweit , Russell King , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Fidelio Lawson Subject: Re: [PATCH v3 1/3] net: dsa: microchip: implement KSZ87xx Module 3 low-loss cable errata Message-ID: <03040421-89e7-4422-9fb5-0367a34323e4@lunn.ch> References: <20260414-ksz87xx_errata_low_loss_connections-v3-0-0e3838ca98c9@exotec.com> <20260414-ksz87xx_errata_low_loss_connections-v3-1-0e3838ca98c9@exotec.com> <712cc46a-5ceb-4f0f-88bb-fa0a47002258@nabladev.com> <84e24758-2f59-44ca-a9b8-a46094578f83@gmail.com> 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: <84e24758-2f59-44ca-a9b8-a46094578f83@gmail.com> > Yes, I think a reasonable compromise could be to expose three tunables: > > - a boolean "short-cable" tunable, which applies the known good settings > (LPF 62 MHz BW, DSP EQ initial value 0). > > - an integer LPF bandwidth tunable, for advanced use cases where further > tuning is needed; > > - an integer DSP EQ initial value tunable, for the same advanced cases. > > The boolean tunable would follow the KISS principle and cover the common > scenario, while the more granular controls would remain optional. How do the three interact? Do you need to first enable short-cable before you set LPG bandwidth or DSP EQ? If it is not enabled, do you get -EINVAL? It seems like having extack would be useful to return informative error messages to user space, however, that requires netlink ethtool. And ETHTOOL_PHY_STUNABLE has not been added to netlink ethtool yet :-( Andrew