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 B6D82CA9EA9 for ; Fri, 18 Oct 2019 16:01:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8A96821897 for ; Fri, 18 Oct 2019 16:01:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b="BEErwb0u" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2501970AbfJRQBX (ORCPT ); Fri, 18 Oct 2019 12:01:23 -0400 Received: from vps0.lunn.ch ([185.16.172.187]:52686 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726506AbfJRQBW (ORCPT ); Fri, 18 Oct 2019 12:01:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender: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=SMevRHn5yAEfndygCJGs4e6HW+7R6WGQ8pVjp6LF3ck=; b=BEErwb0u6hMrDSuQYoY0HlkHWz 0gIyUCWa/abTfBKoco0WYf/7oWnJTsQPdB5bRDVguZACXvtAPCqpBkBv5AM1Nt8GCXigGHD9QWJ8V mnp39WvOEaavIcJj5BbQEhNfzkU96y4Vr7cmmnKMZzaBeWy0EipOK5A00odRjeI9n6rA=; Received: from andrew by vps0.lunn.ch with local (Exim 4.92.2) (envelope-from ) id 1iLUgm-0001qG-Py; Fri, 18 Oct 2019 18:01:16 +0200 Date: Fri, 18 Oct 2019 18:01:16 +0200 From: Andrew Lunn To: Vladimir Oltean Cc: Russell King - ARM Linux admin , Florian Fainelli , netdev , "David S. Miller" , open list , Heiner Kallweit , bcm-kernel-feedback-list@broadcom.com, cphealy@gmail.com, Jose Abreu Subject: Re: [PATCH net-next 2/2] net: phy: Add ability to debug RGMII connections Message-ID: <20191018160116.GD24810@lunn.ch> References: <20191015224953.24199-3-f.fainelli@gmail.com> <4feb3979-1d59-4ad3-b2f1-90d82cfbdf54@gmail.com> <20191018130121.GK4780@lunn.ch> <20191018132316.GI25745@shell.armlinux.org.uk> <20191018135411.GJ25745@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > I don't think you are following the big picture of what I am saying. I > was trying to follow Florian's intention (first make sure I understand > it) and suggest that the FCS checking code in the patch he submitted > is not doing what it was intended to. I am getting apparent FCS > mismatches reported by the program, when I know full well that the MAC > I am testing on would have dropped those frames were they really > invalid. I think this FCS check is not needed. If we feed the MAC random data, something like 1 in 65535 will have a valid FCS and get passed up. I've not seen this happen with Ethernet, but i have seen other network technologies wrong decoding noise on the line and passing up frames with around 1 in 65536 probability. But then having the correct Ethertype is another 1 in 65536. So it seem pretty improbably we do receiver a packet in this method which is bad. So i would say, any packet received here is a good packet, and indicate the RGMII mode works. If we don't receive a packet, the mode is very probably bad. Andrew