net: phy: mscc: consolidate a common RGMII delay implementation

It looks like the VSC8584 PHY driver is rolling its own RGMII delay
configuration code, despite the fact that the logic is mostly the same.

In fact only the register layout and position for the RGMII controls has
changed. So we need to adapt and parameterize the PHY-dependent bit
fields when calling the new generic function.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/mscc/mscc.h

@@ -161,25 +161,15 @@ enum rgmii_clock_delay {
 /* Extended Page 2 Registers */
 #define MSCC_PHY_CU_PMD_TX_CNTL		  16
 
-#define MSCC_PHY_RGMII_SETTINGS		  18
-#define RGMII_SKEW_RX_POS		  1
-#define RGMII_SKEW_TX_POS		  4
-
-/* RGMII skew values, in ns */
-#define VSC8584_RGMII_SKEW_0_2		  0
-#define VSC8584_RGMII_SKEW_0_8		  1
-#define VSC8584_RGMII_SKEW_1_1		  2
-#define VSC8584_RGMII_SKEW_1_7		  3
-#define VSC8584_RGMII_SKEW_2_0		  4
-#define VSC8584_RGMII_SKEW_2_3		  5
-#define VSC8584_RGMII_SKEW_2_6		  6
-#define VSC8584_RGMII_SKEW_3_4		  7
-
-#define MSCC_PHY_RGMII_CNTL		  20
-#define RGMII_RX_CLK_DELAY_MASK		  0x0070
-#define RGMII_RX_CLK_DELAY_POS		  4
-#define RGMII_TX_CLK_DELAY_MASK		  0x0007
-#define RGMII_TX_CLK_DELAY_POS		  0
+/* RGMII setting controls at address 18E2, for VSC8572 and similar */
+#define VSC8572_RGMII_CNTL		  18
+#define VSC8572_RGMII_RX_DELAY_MASK	  0x000E
+#define VSC8572_RGMII_TX_DELAY_MASK	  0x0070
+
+/* RGMII controls at address 20E2, for VSC8502 and similar */
+#define VSC8502_RGMII_CNTL		  20
+#define VSC8502_RGMII_RX_DELAY_MASK	  0x0070
+#define VSC8502_RGMII_TX_DELAY_MASK	  0x0007
 
 #define MSCC_PHY_WOL_LOWER_MAC_ADDR	  21
 #define MSCC_PHY_WOL_MID_MAC_ADDR	  22

drivers/net/phy/mscc/mscc_main.c

@@ -520,28 +520,34 @@ static int vsc85xx_mac_if_set(struct phy_device *phydev,
 	return rc;
 }
 
-static int vsc85xx_default_config(struct phy_device *phydev)
+/* Set the RGMII RX and TX clock skews individually, according to the PHY
+ * interface type, to:
+ *  * 0.2 ns (their default, and lowest, hardware value) if delays should
+ *    not be enabled
+ *  * 2.0 ns (which causes the data to be sampled at exactly half way between
+ *    clock transitions at 1000 Mbps) if delays should be enabled
+ */
+static int vsc85xx_rgmii_set_skews(struct phy_device *phydev, u32 rgmii_cntl,
+				   u16 rgmii_rx_delay_mask,
+				   u16 rgmii_tx_delay_mask)
 {
+	u16 rgmii_rx_delay_pos = ffs(rgmii_rx_delay_mask) - 1;
+	u16 rgmii_tx_delay_pos = ffs(rgmii_tx_delay_mask) - 1;
 	u16 reg_val = 0;
 	int rc;
 
-	phydev->mdix_ctrl = ETH_TP_MDI_AUTO;
-
-	if (!phy_interface_mode_is_rgmii(phydev->interface))
-		return 0;
-
 	mutex_lock(&phydev->lock);
 
 	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID ||
 	    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID)
-		reg_val |= RGMII_CLK_DELAY_2_0_NS << RGMII_RX_CLK_DELAY_POS;
+		reg_val |= RGMII_CLK_DELAY_2_0_NS << rgmii_rx_delay_pos;
 	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID ||
 	    phydev->interface == PHY_INTERFACE_MODE_RGMII_ID)
-		reg_val |= RGMII_CLK_DELAY_2_0_NS << RGMII_TX_CLK_DELAY_POS;
+		reg_val |= RGMII_CLK_DELAY_2_0_NS << rgmii_tx_delay_pos;
 
 	rc = phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_2,
-			      MSCC_PHY_RGMII_CNTL,
-			      RGMII_RX_CLK_DELAY_MASK | RGMII_TX_CLK_DELAY_MASK,
+			      rgmii_cntl,
+			      rgmii_rx_delay_mask | rgmii_tx_delay_mask,
 			      reg_val);
 
 	mutex_unlock(&phydev->lock);
@@ -549,6 +555,23 @@ static int vsc85xx_default_config(struct phy_device *phydev)
 	return rc;
 }
 
+static int vsc85xx_default_config(struct phy_device *phydev)
+{
+	int rc;
+
+	phydev->mdix_ctrl = ETH_TP_MDI_AUTO;
+
+	if (phy_interface_mode_is_rgmii(phydev->interface)) {
+		rc = vsc85xx_rgmii_set_skews(phydev, VSC8502_RGMII_CNTL,
+					     VSC8502_RGMII_RX_DELAY_MASK,
+					     VSC8502_RGMII_TX_DELAY_MASK);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
 static int vsc85xx_get_tunable(struct phy_device *phydev,
 			       struct ethtool_tunable *tuna, void *data)
 {
@@ -1301,32 +1324,6 @@ static bool vsc8584_is_pkg_init(struct phy_device *phydev, bool reversed)
 	return false;
 }
 
-static void vsc8584_rgmii_set_skews(struct phy_device *phydev)
-{
-	u32 skew_rx, skew_tx;
-
-	/* We first set the Rx and Tx skews to their default value in h/w
-	 * (0.2 ns).
-	 */
-	skew_rx = VSC8584_RGMII_SKEW_0_2;
-	skew_tx = VSC8584_RGMII_SKEW_0_2;
-
-	/* We then set the skews based on the interface mode. */
-	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
-	    phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID)
-		skew_rx = VSC8584_RGMII_SKEW_2_0;
-	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
-	    phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID)
-		skew_tx = VSC8584_RGMII_SKEW_2_0;
-
-	/* Finally we apply the skews configuration. */
-	phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_2,
-			 MSCC_PHY_RGMII_SETTINGS,
-			 (0x7 << RGMII_SKEW_RX_POS) | (0x7 << RGMII_SKEW_TX_POS),
-			 (skew_rx << RGMII_SKEW_RX_POS) |
-			 (skew_tx << RGMII_SKEW_TX_POS));
-}
-
 static int vsc8584_config_init(struct phy_device *phydev)
 {
 	struct vsc8531_private *vsc8531 = phydev->priv;
@@ -1461,8 +1458,13 @@ static int vsc8584_config_init(struct phy_device *phydev)
 	if (ret)
 		return ret;
 
-	if (phy_interface_is_rgmii(phydev))
-		vsc8584_rgmii_set_skews(phydev);
+	if (phy_interface_is_rgmii(phydev)) {
+		ret = vsc85xx_rgmii_set_skews(phydev, VSC8572_RGMII_CNTL,
+					      VSC8572_RGMII_RX_DELAY_MASK,
+					      VSC8572_RGMII_TX_DELAY_MASK);
+		if (ret)
+			return ret;
+	}
 
 	ret = genphy_soft_reset(phydev);
 	if (ret)