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 X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F8D2C433E0 for ; Sun, 24 May 2020 22:43:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DAC3020823 for ; Sun, 24 May 2020 22:43:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="xecVH8CH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388616AbgEXWnD (ORCPT ); Sun, 24 May 2020 18:43:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388599AbgEXWm6 (ORCPT ); Sun, 24 May 2020 18:42:58 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:3201:214:fdff:fe10:1be6]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94929C061A0E; Sun, 24 May 2020 15:42:57 -0700 (PDT) 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=/LrcVT1btKqn93FHBR9FP0SUTFOHTkhJS9hiLmevHSo=; b=xecVH8CHbE83mzbEnf8mS+FMY U4ieHHS01dJCZ4BuTA+QeCjdyjeOIlRgKaIX1Yx7C27ddnq741lWEIcZlX1GRqdfJB0pKlOxwUrx7 hLljnnD4Rt8oUazx0i/DcwQ6u9/+AytPla4NiDP7e2fxtlL/A3fREie/+cRtMgEO+oCG7gCnnBUfV J3XUsAhvc5qkX5FqeiAiiEc55DsHF5NOa3lUxNBWCL/OcLTlgLl2iz/xvfo4djgvHGcVZEr0/E0+F DzQsSthg8WFKYSAI5Xr4BUg0vtE1PikXo19roLmLfUe8qE23leXMDtXO4rWvb2Et4zIDHLdzC+yUb LfYC6+bTg==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:36528) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jczK4-0003I2-Cx; Sun, 24 May 2020 23:42:29 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1jczJw-0003ha-1W; Sun, 24 May 2020 23:42:16 +0100 Date: Sun, 24 May 2020 23:42:16 +0100 From: Russell King - ARM Linux admin To: Pavel Machek Cc: Christian Herber , Oleksij Rempel , Andrew Lunn , "David S. Miller" , Florian Fainelli , Heiner Kallweit , Jakub Kicinski , Jonathan Corbet , Michal Kubecek , David Jander , "kernel@pengutronix.de" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "mkl@pengutronix.de" , Marek Vasut Subject: Re: signal quality and cable diagnostic Message-ID: <20200524224215.GE1551@shell.armlinux.org.uk> References: <20200524212757.GC1192@bug> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200524212757.GC1192@bug> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sun, May 24, 2020 at 11:27:57PM +0200, Pavel Machek wrote: > > > The SNR seems to be most universal value, when it comes to comparing > > > different situations (different links and different PHYs). The > > > resolution of BER is not that detailed, for the NXP PHY is says only > > > "BER below 1e-10" or not. > > > > The point I was trying to make is that SQI is intentionally called SQI and NOT SNR, because it is not a measure for SNR. The standard only suggest a mapping of SNR to SQI, but vendors do not need to comply to that or report that. The only mandatory requirement is linking to BER. BER is also what would be required by a user, as this is the metric that determines what happens to your traffic, not the SNR. > > > > So when it comes to KAPI parameters, I see the following options > > - SQI only > > - SQI + plus indication of SQI level at which BER<10^-10 (this is the only required and standardized information) > > - SQI + BER range (best for users, but requires input from the silicon vendors) > > Last option looks best to me... and it will mean that hopefully silicon vendors standartize > something in future. It already has been for > 1G PHYs, but whether they implement it is another question altogether. It's a 22-bit limiting counter in the PCS. There's also indications of "high BER". -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC for 0.8m (est. 1762m) line in suburbia: sync at 13.1Mbps down 424kbps up