[PATCH] net: bcmgenet: Fix attaching to PYH failed on RPi 4B

[Jian-Hong Pan]

The Broadcom UniMAC MDIO bus comes too late. So, GENET cannot find the
ethernet PHY on UniMAC MDIO bus. This leads GENET fail to attach the
PHY.

bcmgenet fd580000.ethernet: GENET 5.0 EPHY: 0x0000
...
could not attach to PHY
bcmgenet fd580000.ethernet eth0: failed to connect to PHY
uart-pl011 fe201000.serial: no DMA platform data
libphy: bcmgenet MII bus: probed
...
unimac-mdio unimac-mdio.-19: Broadcom UniMAC MDIO bus

This patch makes GENET try to connect the PHY up to 3 times. Also, waits
a while between each time for mdio-bcm-unimac module's loading and
probing.

Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=213485
Signed-off-by: Jian-Hong Pan <jhp@xxxxxxxxxxxxx>
---
 drivers/net/ethernet/broadcom/genet/bcmmii.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmmii.c b/drivers/net/ethernet/broadcom/genet/bcmmii.c
index 5335244e4577..64f244471fd3 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmmii.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmmii.c
@@ -289,6 +289,7 @@ int bcmgenet_mii_probe(struct net_device *dev)
 	struct phy_device *phydev;
 	u32 phy_flags = 0;
 	int ret;
+	int i;
 
 	/* Communicate the integrated PHY revision */
 	if (priv->internal_phy)
@@ -301,8 +302,22 @@ int bcmgenet_mii_probe(struct net_device *dev)
 	priv->old_pause = -1;
 
 	if (dn) {
-		phydev = of_phy_connect(dev, priv->phy_dn, bcmgenet_mii_setup,
-					phy_flags, priv->phy_interface);
+		/* Try to connect the PHY on UniMAC DMIO bus up to 3 times.
+		 * Wait a while between each time for mdio-bcm-unimac module's
+		 * loading and probing.
+		 */
+		phydev = NULL;
+		for (i = 1; i < 4 && !phydev; i++) {
+			netdev_info(dev,
+				    "connect %s on UniMAC MDIO bus %d time",
+				    priv->phy_dn->full_name, i);
+			phydev = of_phy_connect(dev, priv->phy_dn,
+						bcmgenet_mii_setup,
+						phy_flags, priv->phy_interface);
+			if (!phydev && i < 3)
+				msleep(500);
+		}
+
 		if (!phydev) {
 			pr_err("could not attach to PHY\n");
 			return -ENODEV;
-- 
2.32.0