net: phy: consider AN_RESTART status when reading link status

After configuring and restarting aneg we immediately try to read the
link status. On some systems the PHY may not yet have cleared the
"aneg complete" and "link up" bits, resulting in a false link-up
signal. See [0] for a report.
Clause 22 and 45 both require the PHY to keep the AN_RESTART
bit set until the PHY actually starts auto-negotiation.
Let's consider this in the generic functions for reading link status.
The commit marked as fixed is the first one where the patch applies
cleanly.

[0] https://marc.info/?t=156518400300003&r=1&w=2

Fixes: c1164bb1a631 ("net: phy: check PMAPMD link status only in genphy_c45_read_link")
Tested-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>

diff --git a/drivers/net/phy/phy-c45.c b/drivers/net/phy/phy-c45.c
index b9d4145781caa092625adb94214549a02b66fd50..58bb25e4af1066ab8d4cc624884e247e37c6c5a7 100644 (file)
--- a/drivers/net/phy/phy-c45.c
+++ b/drivers/net/phy/phy-c45.c
@@ -219,6 +219,20 @@ int genphy_c45_read_link(struct phy_device *phydev)
        int val, devad;
        bool link = true;
 
+       if (phydev->c45_ids.devices_in_package & MDIO_DEVS_AN) {
+               val = phy_read_mmd(phydev, MDIO_MMD_AN, MDIO_CTRL1);
+               if (val < 0)
+                       return val;
+
+               /* Autoneg is being started, therefore disregard current
+                * link status and report link as down.
+                */
+               if (val & MDIO_AN_CTRL1_RESTART) {
+                       phydev->link = 0;
+                       return 0;
+               }
+       }
+
        while (mmd_mask && link) {
                devad = __ffs(mmd_mask);
                mmd_mask &= ~BIT(devad);

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 7ddd91df99e3dc24db6d374ba7b5e911c4716f47..27ebc2c6c2d0c4eb111f39a5596f50d976ca4a1a 100644 (file)
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1752,7 +1752,17 @@ EXPORT_SYMBOL(genphy_aneg_done);
  */
 int genphy_update_link(struct phy_device *phydev)
 {
-       int status;
+       int status = 0, bmcr;
+
+       bmcr = phy_read(phydev, MII_BMCR);
+       if (bmcr < 0)
+               return bmcr;
+
+       /* Autoneg is being started, therefore disregard BMSR value and
+        * report link as down.
+        */
+       if (bmcr & BMCR_ANRESTART)
+               goto done;
 
        /* The link state is latched low so that momentary link
         * drops can be detected. Do not double-read the status