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net: phy: bcm7xxx: workaround MDIO management controller initial read

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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 <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Fainelli 2015-06-26 10:39:04 -07:00 committed by David S. Miller
parent 8031612d7f
commit 8e346e1594
1 changed files with 7 additions and 0 deletions
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7
drivers/net/phy/bcm7xxx.c
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@ -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);