If the auto-negotiation fails to establish a gigabit link, the phy can try to 'down-shift': it resets the bits in MII_CTRL1000 to stop advertising 1Gbps and retries the negotiation at 100Mbps.
From commit 5502b218e001 ("net: phy: use phy_resolve_aneg_linkmode
in genphy_read_status") the content of MII_CTRL1000 is not checked anymore at the end of the negotiation, preventing the detection of phy 'down-shift'. In case of 'down-shift' phydev->advertising gets out-of-sync wrt MII_CTRL1000 and still includes modes that the phy have already dropped. The link partner could still advertise higher speeds, while the link is established at one of the common lower speeds. The logic 'and' in phy_resolve_aneg_linkmode() between phydev->advertising and phydev->lp_advertising will report an incorrect mode.
Issue detected with a local phy rtl8211f connected with a gigabit capable router through a two-pairs network cable.
After auto-negotiation, read back MII_CTRL1000 and mask-out from phydev->advertising the modes that have been eventually discarded due to the 'down-shift'.
Fixes: 5502b218e001 ("net: phy: use phy_resolve_aneg_linkmode in genphy_read_status") Cc: stable@vger.kernel.org # v5.1+ Signed-off-by: Antonio Borneo antonio.borneo@st.com Link: https://lore.kernel.org/r/478f871a-583d-01f1-9cc5-2eea56d8c2a7@huawei.com --- To: Andrew Lunn andrew@lunn.ch To: Heiner Kallweit hkallweit1@gmail.com To: Russell King linux@armlinux.org.uk To: "David S. Miller" davem@davemloft.net To: Jakub Kicinski kuba@kernel.org To: netdev@vger.kernel.org To: Yonglong Liu liuyonglong@huawei.com Cc: linuxarm@huawei.com Cc: Salil Mehta salil.mehta@huawei.com Cc: linux-stm32@st-md-mailman.stormreply.com Cc: linux-kernel@vger.kernel.org Cc: Antonio Borneo antonio.borneo@st.com
drivers/net/phy/phy_device.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c index 5dab6be6fc38..5d1060aa1b25 100644 --- a/drivers/net/phy/phy_device.c +++ b/drivers/net/phy/phy_device.c @@ -2331,7 +2331,7 @@ EXPORT_SYMBOL(genphy_read_status_fixed); */ int genphy_read_status(struct phy_device *phydev) { - int err, old_link = phydev->link; + int adv, err, old_link = phydev->link;
/* Update the link, but return if there was an error */ err = genphy_update_link(phydev); @@ -2356,6 +2356,14 @@ int genphy_read_status(struct phy_device *phydev) return err;
if (phydev->autoneg == AUTONEG_ENABLE && phydev->autoneg_complete) { + if (phydev->is_gigabit_capable) { + adv = phy_read(phydev, MII_CTRL1000); + if (adv < 0) + return adv; + /* update advertising in case of 'down-shift' */ + mii_ctrl1000_mod_linkmode_adv_t(phydev->advertising, + adv); + } phy_resolve_aneg_linkmode(phydev); } else if (phydev->autoneg == AUTONEG_DISABLE) { err = genphy_read_status_fixed(phydev);
base-commit: d549699048b4b5c22dd710455bcdb76966e55aa3