From 8e346e1594bab6c06b6b4d2938c881729b03041d Mon Sep 17 00:00:00 2001 From: Florian Fainelli Date: Fri, 26 Jun 2015 10:39:04 -0700 Subject: [PATCH] net: phy: bcm7xxx: workaround MDIO management controller initial read The initial MDIO read or write towards the BCM7xxx integrated PHY may fail, workaround this by inserting a dummy MII_BMSR read to force the MDIO management controller to see at least one valid transaction and get out of stuck state out of reset. Signed-off-by: Florian Fainelli Signed-off-by: David S. Miller --- drivers/net/phy/bcm7xxx.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/net/phy/bcm7xxx.c b/drivers/net/phy/bcm7xxx.c index 4dea85bfc545..6b701b3ded74 100644 --- a/drivers/net/phy/bcm7xxx.c +++ b/drivers/net/phy/bcm7xxx.c @@ -246,6 +246,13 @@ static int bcm7xxx_28nm_config_init(struct phy_device *phydev) pr_info_once("%s: %s PHY revision: 0x%02x, patch: %d\n", dev_name(&phydev->dev), phydev->drv->name, rev, patch); + /* Dummy read to a register to workaround an issue upon reset where the + * internal inverter may not allow the first MDIO transaction to pass + * the MDIO management controller and make us return 0xffff for such + * reads. + */ + phy_read(phydev, MII_BMSR); + switch (rev) { case 0xb0: ret = bcm7xxx_28nm_b0_afe_config_init(phydev);