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Fri, 9 Jun 2023 07:37:21 +0000 (UTC) Date: Fri, 9 Jun 2023 10:09:12 +0200 From: Maxime Chevallier To: "Russell King (Oracle)" 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: <20230609100912.70a2bbc1@pc-7.home> In-Reply-To: References: <20230608163415.511762-1-maxime.chevallier@bootlin.com> <20230608163415.511762-4-maxime.chevallier@bootlin.com> <20230608195330.476fca86@pc-7.home> Organization: Bootlin X-Mailer: Claws Mail 4.1.1 (GTK 3.24.37; x86_64-redhat-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230609_003729_962762_B74788AF X-CRM114-Status: GOOD ( 24.76 ) 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 Hi Russell, On Thu, 8 Jun 2023 18:30:41 +0100 "Russell King (Oracle)" wrote: > 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: Indeed :( thanks for the clarifications. > +#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. > Indeed, thanks... I'll respin with a proper implementation this time. Thanks for spotting this Maxime _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel