net: phy: Add 100 base-x mode

Sparx-5 supports this mode and it is missing in the PHY core.
Signed-off-by: Bjarni Jonasson <bjarni.jonasson@microchip.com>
Reviewed-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/phy.rst

@@ -286,6 +286,11 @@ Some of the interface modes are described below:
     Note: due to legacy usage, some 10GBASE-R usage incorrectly makes
     use of this definition.
 
+``PHY_INTERFACE_MODE_100BASEX``
+    This defines IEEE 802.3 Clause 24.  The link operates at a fixed data
+    rate of 125Mpbs using a 4B/5B encoding scheme, resulting in an underlying
+    data rate of 100Mpbs.
+
 Pause frames / flow control
 ===========================
 

include/linux/phy.h

@@ -104,6 +104,7 @@ extern const int phy_10gbit_features_array[1];
  * @PHY_INTERFACE_MODE_MOCA: Multimedia over Coax
  * @PHY_INTERFACE_MODE_QSGMII: Quad SGMII
  * @PHY_INTERFACE_MODE_TRGMII: Turbo RGMII
+ * @PHY_INTERFACE_MODE_100BASEX: 100 BaseX
  * @PHY_INTERFACE_MODE_1000BASEX: 1000 BaseX
  * @PHY_INTERFACE_MODE_2500BASEX: 2500 BaseX
  * @PHY_INTERFACE_MODE_RXAUI: Reduced XAUI
@@ -135,6 +136,7 @@ typedef enum {
 	PHY_INTERFACE_MODE_MOCA,
 	PHY_INTERFACE_MODE_QSGMII,
 	PHY_INTERFACE_MODE_TRGMII,
+	PHY_INTERFACE_MODE_100BASEX,
 	PHY_INTERFACE_MODE_1000BASEX,
 	PHY_INTERFACE_MODE_2500BASEX,
 	PHY_INTERFACE_MODE_RXAUI,
@@ -217,6 +219,8 @@ static inline const char *phy_modes(phy_interface_t interface)
 		return "usxgmii";
 	case PHY_INTERFACE_MODE_10GKR:
 		return "10gbase-kr";
+	case PHY_INTERFACE_MODE_100BASEX:
+		return "100base-x";
 	default:
 		return "unknown";
 	}