From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Lunn Date: Wed, 3 Nov 2021 01:48:19 +0100 Subject: [Intel-wired-lan] [PATCH v2 net] ixgbe: set X550 MDIO speed before talking to PHY In-Reply-To: <896681e4-fcd7-3187-8e59-75ce0896ebd3@lynx.com> References: <896681e4-fcd7-3187-8e59-75ce0896ebd3@lynx.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: intel-wired-lan@osuosl.org List-ID: On Mon, Nov 01, 2021 at 06:39:36PM -0700, Cyril Novikov wrote: > The MDIO bus speed must be initialized before talking to the PHY the first > time in order to avoid talking to it using a speed that the PHY doesn't > support. > > This fixes HW initialization error -17 (IXGBE_ERR_PHY_ADDR_INVALID) on > Denverton CPUs (a.k.a. the Atom C3000 family) on ports with a 10Gb network > plugged in. On those devices, HLREG0[MDCSPD] resets to 1, which combined > with the 10Gb network results in a 24MHz MDIO speed, which is apparently > too fast for the connected PHY. PHY register reads over MDIO bus return > garbage, leading to initialization failure. > > Reproduced with Linux kernel 4.19 and 5.15-rc7. Can be reproduced using > the following setup: > > * Use an Atom C3000 family system with at least one X552 LAN on the SoC > * Disable PXE or other BIOS network initialization if possible > (the interface must not be initialized before Linux boots) > * Connect a live 10Gb Ethernet cable to an X550 port > * Power cycle (not reset, doesn't always work) the system and boot Linux > * Observe: ixgbe interfaces w/ 10GbE cables plugged in fail with error -17 > > Signed-off-by: Cyril Novikov > Fixes: e84db7272798 ("ixgbe: Introduce function to control MDIO speed") Reviewed-by: Andrew Lunn Andrew