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Miller" , Andrew Lunn , Eric Dumazet , Florian Fainelli , Jakub Kicinski , Paolo Abeni , Woojung Huh , Arun Ramadoss , Lucas Stach , kernel@pengutronix.de, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, UNGLinuxDriver@microchip.com Subject: Re: [PATCH net-next v2 3/3] net: dsa: microchip: lan937x: disable VPHY support Message-ID: <20240701162123.bj2lgsrouik3xtj3@skbuf> References: <20240701085343.3042567-1-o.rempel@pengutronix.de> <20240701085343.3042567-3-o.rempel@pengutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240701085343.3042567-3-o.rempel@pengutronix.de> On Mon, Jul 01, 2024 at 10:53:43AM +0200, Oleksij Rempel wrote: > From: Lucas Stach > > As described by the microchip article "LAN937X - The required > configuration for the external MAC port to operate at RGMII-to-RGMII > 1Gbps link speed." [1]: > > "When VPHY is enabled, the auto-negotiation process following IEEE 802.3 > standard will be triggered and will result in RGMII-to-RGMII signal > failure on the interface because VPHY will try to poll the PHY status > that is not available in the scenario of RGMII-to-RGMII connection > (normally the link partner is usually an external processor). > > Note that when VPHY fails on accessing PHY registers, it will fall back > to 100Mbps speed, it indicates disabling VPHY is optional if you only > need the port to link at 100Mbps speed. > > Again, VPHY must and can only be disabled by writing VPHY_DISABLE bit in > the register below as there is no strapping pin for the control." > > This patch was tested on LAN9372, so far it seems to not to affect VPHY > based clock crossing optimization for the ports with integrated PHYs. > > [1]: https://microchip.my.site.com/s/article/LAN937X-The-required-configuration-for-the-external-MAC-port-to-operate-at-RGMII-to-RGMII-1Gbps-link-speed > > Signed-off-by: Lucas Stach > Signed-off-by: Oleksij Rempel > --- > changes v2: > - reword the comment and link microchip article > --- Reviewed-by: Vladimir Oltean