net: phy: Add helper for fixing RGMII PHY mode based on internal mac delay

The "phy-mode" property of devicetree indicates whether the PCB has
delay now, which means the mac needs to modify the PHY mode based
on whether there is an internal delay in the mac.

This modification is similar for many ethernet drivers. To simplify
code, define the helper phy_fix_phy_mode_for_mac_delays(speed, mac_txid,
mac_rxid) to fix PHY mode based on whether mac adds internal delay.

Suggested-by: Russell King (Oracle) <linux@armlinux.org.uk>
Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20251114003805.494387-3-inochiama@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 46 insertions, 0 deletions

diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
index 605ca20ae192..0c63e6ba2cb0 100644
--- a/drivers/net/phy/phy-core.c
+++ b/drivers/net/phy/phy-core.c
@@ -102,6 +102,49 @@ const char *phy_rate_matching_to_str(int rate_matching)
 EXPORT_SYMBOL_GPL(phy_rate_matching_to_str);
 
 /**
+ * phy_fix_phy_mode_for_mac_delays - Convenience function for fixing PHY
+ * mode based on whether mac adds internal delay
+ *
+ * @interface: The current interface mode of the port
+ * @mac_txid: True if the mac adds internal tx delay
+ * @mac_rxid: True if the mac adds internal rx delay
+ *
+ * Return: fixed PHY mode, or PHY_INTERFACE_MODE_NA if the interface can
+ * not apply the internal delay
+ */
+phy_interface_t phy_fix_phy_mode_for_mac_delays(phy_interface_t interface,
+						bool mac_txid, bool mac_rxid)
+{
+	if (!phy_interface_mode_is_rgmii(interface))
+		return interface;
+
+	if (mac_txid && mac_rxid) {
+		if (interface == PHY_INTERFACE_MODE_RGMII_ID)
+			return PHY_INTERFACE_MODE_RGMII;
+		return PHY_INTERFACE_MODE_NA;
+	}
+
+	if (mac_txid) {
+		if (interface == PHY_INTERFACE_MODE_RGMII_ID)
+			return PHY_INTERFACE_MODE_RGMII_RXID;
+		if (interface == PHY_INTERFACE_MODE_RGMII_TXID)
+			return PHY_INTERFACE_MODE_RGMII;
+		return PHY_INTERFACE_MODE_NA;
+	}
+
+	if (mac_rxid) {
+		if (interface == PHY_INTERFACE_MODE_RGMII_ID)
+			return PHY_INTERFACE_MODE_RGMII_TXID;
+		if (interface == PHY_INTERFACE_MODE_RGMII_RXID)
+			return PHY_INTERFACE_MODE_RGMII;
+		return PHY_INTERFACE_MODE_NA;
+	}
+
+	return interface;
+}
+EXPORT_SYMBOL_GPL(phy_fix_phy_mode_for_mac_delays);
+
+/**
  * phy_interface_num_ports - Return the number of links that can be carried by
  *			     a given MAC-PHY physical link. Returns 0 if this is
  *			     unknown, the number of links else.
diff --git a/include/linux/phy.h b/include/linux/phy.h
index bf5457341ca8..65b0c3ca6a2b 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -2040,6 +2040,9 @@ static inline bool phy_is_pseudo_fixed_link(struct phy_device *phydev)
 	return phydev->is_pseudo_fixed_link;
 }
 
+phy_interface_t phy_fix_phy_mode_for_mac_delays(phy_interface_t interface,
+						bool mac_txid, bool mac_rxid);
+
 int phy_save_page(struct phy_device *phydev);
 int phy_select_page(struct phy_device *phydev, int page);
 int phy_restore_page(struct phy_device *phydev, int oldpage, int ret);