net: phy: micrel: Add KSZ8041FTL fiber mode support

We can't detect the FXEN (fiber mode) bootstrap pin, so configure
it via a boolean device tree property "micrel,fiber-mode".
If it is enabled, auto-negotiation is not supported.
The only available modes are 100base-fx (full duplex and half duplex).

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 43 insertions, 2 deletions

diff --git a/Documentation/devicetree/bindings/net/micrel.txt b/Documentation/devicetree/bindings/net/micrel.txt
index 87496a8c64ab..8d157f0295a5 100644
--- a/Documentation/devicetree/bindings/net/micrel.txt
+++ b/Documentation/devicetree/bindings/net/micrel.txt
@@ -35,3 +35,13 @@ Optional properties:
         supported clocks:
         - KSZ8021, KSZ8031, KSZ8081, KSZ8091: "rmii-ref": The RMII reference
           input clock. Used to determine the XI input clock.
+
+ - micrel,fiber-mode: If present the PHY is configured to operate in fiber mode
+
+        Some PHYs, such as the KSZ8041FTL variant, support fiber mode, enabled
+        by the FXEN boot strapping pin. It can't be determined from the PHY
+        registers whether the PHY is in fiber mode, so this boolean device tree
+        property can be used to describe it.
+
+        In fiber mode, auto-negotiation is disabled and the PHY can only work in
+        100base-fx (full and half duplex) modes.
diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 5a8fefc25157..059f13b60fe0 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -311,6 +311,36 @@ static int kszphy_config_init(struct phy_device *phydev)
         return 0;
 }
 
+static int ksz8041_config_init(struct phy_device *phydev)
+{
+        struct device_node *of_node = phydev->mdio.dev.of_node;
+
+        /* Limit supported and advertised modes in fiber mode */
+        if (of_property_read_bool(of_node, "micrel,fiber-mode")) {
+                phydev->dev_flags |= MICREL_PHY_FXEN;
+                phydev->supported &= SUPPORTED_FIBRE |
+                                     SUPPORTED_100baseT_Full |
+                                     SUPPORTED_100baseT_Half;
+                phydev->advertising &= ADVERTISED_FIBRE |
+                                       ADVERTISED_100baseT_Full |
+                                       ADVERTISED_100baseT_Half;
+                phydev->autoneg = AUTONEG_DISABLE;
+        }
+
+        return kszphy_config_init(phydev);
+}
+
+static int ksz8041_config_aneg(struct phy_device *phydev)
+{
+        /* Skip auto-negotiation in fiber mode */
+        if (phydev->dev_flags & MICREL_PHY_FXEN) {
+                phydev->speed = SPEED_100;
+                return 0;
+        }
+
+        return genphy_config_aneg(phydev);
+}
+
 static int ksz9021_load_values_from_of(struct phy_device *phydev,
                                        const struct device_node *of_node,
                                        u16 reg,
@@ -788,8 +818,8 @@ static struct phy_driver ksphy_driver[] = {
         .flags          = PHY_HAS_MAGICANEG | PHY_HAS_INTERRUPT,
         .driver_data    = &ksz8041_type,
         .probe          = kszphy_probe,
-        .config_init    = kszphy_config_init,
-        .config_aneg    = genphy_config_aneg,
+        .config_init    = ksz8041_config_init,
+        .config_aneg    = ksz8041_config_aneg,
         .read_status    = genphy_read_status,
         .ack_interrupt  = kszphy_ack_interrupt,
         .config_intr    = kszphy_config_intr,
diff --git a/include/linux/micrel_phy.h b/include/linux/micrel_phy.h
index 2e5b194b9b19..257173e0095e 100644
--- a/include/linux/micrel_phy.h
+++ b/include/linux/micrel_phy.h
@@ -37,6 +37,7 @@
 
 /* struct phy_device dev_flags definitions */
 #define MICREL_PHY_50MHZ_CLK    0x00000001
+#define MICREL_PHY_FXEN         0x00000002
 
 #define MICREL_KSZ9021_EXTREG_CTRL      0xB
 #define MICREL_KSZ9021_EXTREG_DATA_WRITE        0xC