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Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:46416) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1q7JTA-0000k3-O7; Thu, 08 Jun 2023 18:30:44 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1q7JT7-0000zs-Ge; Thu, 08 Jun 2023 18:30:41 +0100 Date: Thu, 8 Jun 2023 18:30:41 +0100 From: "Russell King (Oracle)" To: Maxime Chevallier Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com, Andrew Lunn , Florian Fainelli , Heiner Kallweit , linux-arm-kernel@lists.infradead.org, Horatiu.Vultur@microchip.com, Allan.Nielsen@microchip.com, UNGLinuxDriver@microchip.com, Vladimir Oltean Subject: Re: [PATCH net 2/2] net: phylink: use USXGMII control-word format to parse Q-USGMII word Message-ID: References: <20230608163415.511762-1-maxime.chevallier@bootlin.com> <20230608163415.511762-4-maxime.chevallier@bootlin.com> <20230608195330.476fca86@pc-7.home> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230608195330.476fca86@pc-7.home> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230608_103050_945562_B9F97D45 X-CRM114-Status: GOOD ( 19.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jun 08, 2023 at 07:53:30PM +0200, Maxime Chevallier wrote: > Hi Russell, > > On Thu, 8 Jun 2023 17:32:52 +0100 > "Russell King (Oracle)" wrote: > > > On Thu, Jun 08, 2023 at 06:34:15PM +0200, Maxime Chevallier wrote: > > > diff --git a/include/uapi/linux/mdio.h b/include/uapi/linux/mdio.h > > > index 256b463e47a6..1d20a9082507 100644 > > > --- a/include/uapi/linux/mdio.h > > > +++ b/include/uapi/linux/mdio.h > > > @@ -444,4 +444,7 @@ static inline __u16 mdio_phy_id_c45(int prtad, int devad) > > > #define MDIO_USXGMII_5000FULL 0x1a00 /* 5000Mbps full-duplex */ > > > #define MDIO_USXGMII_LINK 0x8000 /* PHY link with copper-side partner */ > > > > > > +/* Usgmii control word is based on Usxgmii, masking away 2.5, 5 and 10Gbps */ > > > +#define MDIO_USGMII_SPD_MASK 0x0600 > > > > This isn't correct: > > > > 11:9 Speed: Bit 11, 10, 9: > > 1 1 1 to 011 = Reserved > > 0 1 0 = 1000 Mbps: 1000BASE-TX, 1000BASE-X > > 0 0 1 = 100 Mbps: 100BASE-TX, 100BASE-FX > > 0 0 0 = 10 Mbps: 10BASET, 10BASE2, 10BASE5 > > > > If we only look at bits 10 and 9, then we're interpreting the reserved > > combinations as valid as well. > > That's why I rewrote the decoding helper instead of simply masking away > the extra bit, so that we exclude the 0 1 1 combination ( 10G speed ). I don't think you've understood my comment properly. Here is what the code is doing: +#define MDIO_USGMII_SPD_MASK 0x0600 + switch (lpa & MDIO_USGMII_SPD_MASK) { #define MDIO_USXGMII_10 0x0000 /* 10Mbps */ + case MDIO_USXGMII_10: + state->speed = SPEED_10; + break; #define MDIO_USXGMII_100 0x0200 /* 100Mbps */ + case MDIO_USXGMII_100: + state->speed = SPEED_100; + break; #define MDIO_USXGMII_1000 0x0400 /* 1000Mbps */ + case MDIO_USXGMII_1000: + state->speed = SPEED_1000; + break; + default: + state->link = false; + return; + } So, this will decode bits 11:9 as: 000 10Mbps 001 100Mbps 010 1000Mgps 011 link = false 100 10Mbps 101 100Mbps 110 1000Mbps 111 link = false Whereas, USGMII says the last four are all reserved. Why does this happen? Because the mask is defined as: +#define MDIO_USGMII_SPD_MASK 0x0600 which only covers bits 10 and 9, masking off bit 11. However, bit 11 is _still_ part of the field, and if it's set, then it is a "reserved" speed. We should not be just ignoring bit 11. I hope that helps to clarify. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel 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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 929A1C7EE25 for ; Thu, 8 Jun 2023 17:30:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233740AbjFHRax (ORCPT ); Thu, 8 Jun 2023 13:30:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52086 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232448AbjFHRat (ORCPT ); Thu, 8 Jun 2023 13:30:49 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F1C39E; Thu, 8 Jun 2023 10:30:48 -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=vhx0DrAoIURoUAWg1ewcKT6wKdBRWd/M6bB7nEvVkQ4=; b=nnMgt/Q8pqPmW6oH0ol5FDxWVE 4+dKGLaAaU5jYQS8EukKGsBEIDgiPtKCqz21VrvEskHtRHuLtZaK/MmfAXWolrSXUTz3Mzkl4A4dJ QYakt1Sclc3bGVaXPTPh+brvZFpGePJzHRr3soWdAssAv+1r25L5HW7c23xBWcETTbooMiCc5V6U9 e4bLIxU0LXDu39o72xKtlgCQ68sI3PR7QaigfeqMrFsCxfnVMqswPBuy6WsameRAz0fw/AoB/nzB6 DPLosymMlKwiKCzl/QOBvPSSAcuatPc04oveZKL2w7pQm2sMwkuaPc38R7VKuBkMKYbi8eB4+GCWS 7qsfSc4g==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:46416) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1q7JTA-0000k3-O7; Thu, 08 Jun 2023 18:30:44 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1q7JT7-0000zs-Ge; Thu, 08 Jun 2023 18:30:41 +0100 Date: Thu, 8 Jun 2023 18:30:41 +0100 From: "Russell King (Oracle)" To: Maxime Chevallier Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com, Andrew Lunn , Florian Fainelli , Heiner Kallweit , linux-arm-kernel@lists.infradead.org, Horatiu.Vultur@microchip.com, Allan.Nielsen@microchip.com, UNGLinuxDriver@microchip.com, Vladimir Oltean Subject: Re: [PATCH net 2/2] net: phylink: use USXGMII control-word format to parse Q-USGMII word Message-ID: References: <20230608163415.511762-1-maxime.chevallier@bootlin.com> <20230608163415.511762-4-maxime.chevallier@bootlin.com> <20230608195330.476fca86@pc-7.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230608195330.476fca86@pc-7.home> Sender: Russell King (Oracle) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 08, 2023 at 07:53:30PM +0200, Maxime Chevallier wrote: > Hi Russell, > > On Thu, 8 Jun 2023 17:32:52 +0100 > "Russell King (Oracle)" wrote: > > > On Thu, Jun 08, 2023 at 06:34:15PM +0200, Maxime Chevallier wrote: > > > diff --git a/include/uapi/linux/mdio.h b/include/uapi/linux/mdio.h > > > index 256b463e47a6..1d20a9082507 100644 > > > --- a/include/uapi/linux/mdio.h > > > +++ b/include/uapi/linux/mdio.h > > > @@ -444,4 +444,7 @@ static inline __u16 mdio_phy_id_c45(int prtad, int devad) > > > #define MDIO_USXGMII_5000FULL 0x1a00 /* 5000Mbps full-duplex */ > > > #define MDIO_USXGMII_LINK 0x8000 /* PHY link with copper-side partner */ > > > > > > +/* Usgmii control word is based on Usxgmii, masking away 2.5, 5 and 10Gbps */ > > > +#define MDIO_USGMII_SPD_MASK 0x0600 > > > > This isn't correct: > > > > 11:9 Speed: Bit 11, 10, 9: > > 1 1 1 to 011 = Reserved > > 0 1 0 = 1000 Mbps: 1000BASE-TX, 1000BASE-X > > 0 0 1 = 100 Mbps: 100BASE-TX, 100BASE-FX > > 0 0 0 = 10 Mbps: 10BASET, 10BASE2, 10BASE5 > > > > If we only look at bits 10 and 9, then we're interpreting the reserved > > combinations as valid as well. > > That's why I rewrote the decoding helper instead of simply masking away > the extra bit, so that we exclude the 0 1 1 combination ( 10G speed ). I don't think you've understood my comment properly. Here is what the code is doing: +#define MDIO_USGMII_SPD_MASK 0x0600 + switch (lpa & MDIO_USGMII_SPD_MASK) { #define MDIO_USXGMII_10 0x0000 /* 10Mbps */ + case MDIO_USXGMII_10: + state->speed = SPEED_10; + break; #define MDIO_USXGMII_100 0x0200 /* 100Mbps */ + case MDIO_USXGMII_100: + state->speed = SPEED_100; + break; #define MDIO_USXGMII_1000 0x0400 /* 1000Mbps */ + case MDIO_USXGMII_1000: + state->speed = SPEED_1000; + break; + default: + state->link = false; + return; + } So, this will decode bits 11:9 as: 000 10Mbps 001 100Mbps 010 1000Mgps 011 link = false 100 10Mbps 101 100Mbps 110 1000Mbps 111 link = false Whereas, USGMII says the last four are all reserved. Why does this happen? Because the mask is defined as: +#define MDIO_USGMII_SPD_MASK 0x0600 which only covers bits 10 and 9, masking off bit 11. However, bit 11 is _still_ part of the field, and if it's set, then it is a "reserved" speed. We should not be just ignoring bit 11. I hope that helps to clarify. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!