[PATCH v3 net 1/1] net: macb: Fix regression breaking non-MDIO fixed-link PHYs

[Ahmad Fatoum]

commit 739de9a1563a ("net: macb: Reorganize macb_mii bringup") broke
initializing macb on the EVB-KSZ9477 eval board.
There, of_mdiobus_register was called even for the fixed-link representing
the RGMII-link to the switch with the result that the driver attempts to
enumerate PHYs on a non-existent MDIO bus:

        libphy: MACB_mii_bus: probed
        mdio_bus f0028000.ethernet-ffffffff: fixed-link has invalid PHY address
        mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 0
        [snip]
        mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 31

The "MDIO" bus registration succeeds regardless, having claimed the reset GPIO,
and calling of_phy_register_fixed_link later on fails because it tries
to claim the same GPIO:

        macb f0028000.ethernet: broken fixed-link specification

Fix this by registering the fixed-link before calling mdiobus_register.

Fixes: 739de9a1563a ("net: macb: Reorganize macb_mii bringup")
Signed-off-by: Ahmad Fatoum <a.fat...@pengutronix.de>
---

Notes:
    Changes since v2:
        Amend Commit message to address the double GPIO registration
        s/SPI/RGMII/ in commit message (SPI is only for switch register access)
        Change error message to include DT path to fixed-link
    Changes since v1:
        Add one more error path for failing to register fixed-link
        Fix a whitespace issue

 drivers/net/ethernet/cadence/macb_main.c | 27 +++++++++++++++---------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c 
b/drivers/net/ethernet/cadence/macb_main.c
index dc09f9a8a49b..f46b854d34b5 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -482,11 +482,6 @@ static int macb_mii_probe(struct net_device *dev)
 
        if (np) {
                if (of_phy_is_fixed_link(np)) {
-                       if (of_phy_register_fixed_link(np) < 0) {
-                               dev_err(&bp->pdev->dev,
-                                       "broken fixed-link specification\n");
-                               return -ENODEV;
-                       }
                        bp->phy_node = of_node_get(np);
                } else {
                        bp->phy_node = of_parse_phandle(np, "phy-handle", 0);
@@ -569,7 +564,7 @@ static int macb_mii_init(struct macb *bp)
 {
        struct macb_platform_data *pdata;
        struct device_node *np;
-       int err;
+       int err = -ENXIO;
 
        /* Enable management port */
        macb_writel(bp, NCR, MACB_BIT(MPE));
@@ -592,12 +587,23 @@ static int macb_mii_init(struct macb *bp)
        dev_set_drvdata(&bp->dev->dev, bp->mii_bus);
 
        np = bp->pdev->dev.of_node;
-       if (pdata)
-               bp->mii_bus->phy_mask = pdata->phy_mask;
+       if (np && of_phy_is_fixed_link(np)) {
+               if (of_phy_register_fixed_link(np) < 0) {
+                       dev_err(&bp->pdev->dev,
+                               "broken fixed-link specification %pOF\n", np);
+                       goto err_out_free_mdiobus;
+               }
+
+               err = mdiobus_register(bp->mii_bus);
+       } else {
+               if (pdata)
+                       bp->mii_bus->phy_mask = pdata->phy_mask;
+
+               err = of_mdiobus_register(bp->mii_bus, np);
+       }
 
-       err = of_mdiobus_register(bp->mii_bus, np);
        if (err)
-               goto err_out_free_mdiobus;
+               goto err_out_free_fixed_link;
 
        err = macb_mii_probe(bp->dev);
        if (err)
@@ -607,6 +613,7 @@ static int macb_mii_init(struct macb *bp)
 
 err_out_unregister_bus:
        mdiobus_unregister(bp->mii_bus);
+err_out_free_fixed_link:
        if (np && of_phy_is_fixed_link(np))
                of_phy_deregister_fixed_link(np);
 err_out_free_mdiobus:
-- 
2.18.0