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 EAD3FC0650F for ; Sun, 11 Aug 2019 16:44:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0E2C208C2 for ; Sun, 11 Aug 2019 16:44:27 +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="Ct70Sbpp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725900AbfHKQo0 (ORCPT ); Sun, 11 Aug 2019 12:44:26 -0400 Received: from vps0.lunn.ch ([185.16.172.187]:51334 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725830AbfHKQo0 (ORCPT ); Sun, 11 Aug 2019 12:44:26 -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=TUcPvdon//cRSTNaWWbwC4+UhxIzQPVa/qaFVB2nzoo=; b=Ct70SbppQ1TFQY+VVbKLFZPGUK Z/BYxeHlpx0IxYzjtXD+/cJf+0EE4vVWDjiisTrNSS4ggIFouIghmcSLX0YESu4YUv5YbWStYOOto Lod9doT6ZCkVmoEMhTvag1I3SkgNwi6Acef3bWdlsmc0C4D1EFANdIcJucrn5uP+I+cA=; Received: from andrew by vps0.lunn.ch with local (Exim 4.89) (envelope-from ) id 1hwqxC-0004Fo-Fq; Sun, 11 Aug 2019 18:44:22 +0200 Date: Sun, 11 Aug 2019 18:44:22 +0200 From: Andrew Lunn To: Russell King - ARM Linux admin Cc: linux-arm-kernel@lists.infradead.org, Fabio Estevam , netdev@vger.kernel.org, Florian Fainelli , Heiner Kallweit Subject: Re: [BUG] fec mdio times out under system stress Message-ID: <20190811164422.GF14290@lunn.ch> References: <20190811133707.GC13294@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190811133707.GC13294@shell.armlinux.org.uk> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > Maybe phylib should retry a number of times - but with read-sensitive > registers, if the read has already completed successfully, and its > just a problem with the FEC MDIO hardware, that could cause issues. Hi Russell At the bus level, MDIO cannot fail. The bits get clocked out, and the bits get clocked in. There is no way for the PHY to stretch the clock as I2C slaves can. There is nothing like the USB NACK, try again later. If something fails, it fails at a higher level, which means it is a driver issue. In this case, the interrupt got delayed, after the timer interrupt. The FEC is also quite unusual in using an interrupt. Most MDIO drivers poll. And if time gets 'stretched' because the system is too busy, generally, the right thing happens anyway. So i don't think it is phylib job to work around this issue. Andrew