net: phy: microchip_t1s: configure collision detection based on PLCA …

…mode

As per LAN8650/1 Rev.B0/B1 AN1760 (Revision F (DS60001760G - June 2024))
and LAN8670/1/2 Rev.C1/C2 AN1699 (Revision E (DS60001699F - June 2024)),
under normal operation, the device should be operated in PLCA mode.
Disabling collision detection is recommended to allow the device to
operate in noisy environments or when reflections and other inherent
transmission line distortion cause poor signal quality. Collision
detection must be re-enabled if the device is configured to operate in
CSMA/CD mode.

Signed-off-by: Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
Link: https://patch.msgid.link/20241010082205.221493-8-parthiban.veerasooran@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/microchip_t1s.c

@@ -26,6 +26,12 @@
 #define LAN865X_REG_CFGPARAM_CTRL 0x00DA
 #define LAN865X_REG_STS2 0x0019
 
+/* Collision Detector Control 0 Register */
+#define LAN86XX_REG_COL_DET_CTRL0	0x0087
+#define COL_DET_CTRL0_ENABLE_BIT_MASK	BIT(15)
+#define COL_DET_ENABLE			BIT(15)
+#define COL_DET_DISABLE			0x0000
+
 #define LAN865X_CFGPARAM_READ_ENABLE BIT(1)
 
 /* The arrays below are pulled from the following table from AN1699
@@ -371,6 +377,36 @@ static int lan867x_revb1_config_init(struct phy_device *phydev)
 	return 0;
 }
 
+/* As per LAN8650/1 Rev.B0/B1 AN1760 (Revision F (DS60001760G - June 2024)) and
+ * LAN8670/1/2 Rev.C1/C2 AN1699 (Revision E (DS60001699F - June 2024)), under
+ * normal operation, the device should be operated in PLCA mode. Disabling
+ * collision detection is recommended to allow the device to operate in noisy
+ * environments or when reflections and other inherent transmission line
+ * distortion cause poor signal quality. Collision detection must be re-enabled
+ * if the device is configured to operate in CSMA/CD mode.
+ *
+ * AN1760: https://www.microchip.com/en-us/application-notes/an1760
+ * AN1699: https://www.microchip.com/en-us/application-notes/an1699
+ */
+static int lan86xx_plca_set_cfg(struct phy_device *phydev,
+				const struct phy_plca_cfg *plca_cfg)
+{
+	int ret;
+
+	ret = genphy_c45_plca_set_cfg(phydev, plca_cfg);
+	if (ret)
+		return ret;
+
+	if (plca_cfg->enabled)
+		return phy_modify_mmd(phydev, MDIO_MMD_VEND2,
+				      LAN86XX_REG_COL_DET_CTRL0,
+				      COL_DET_CTRL0_ENABLE_BIT_MASK,
+				      COL_DET_DISABLE);
+
+	return phy_modify_mmd(phydev, MDIO_MMD_VEND2, LAN86XX_REG_COL_DET_CTRL0,
+			      COL_DET_CTRL0_ENABLE_BIT_MASK, COL_DET_ENABLE);
+}
+
 static int lan86xx_read_status(struct phy_device *phydev)
 {
 	/* The phy has some limitations, namely:
@@ -432,7 +468,7 @@ static struct phy_driver microchip_t1s_driver[] = {
 		.config_init        = lan867x_revc_config_init,
 		.read_status        = lan86xx_read_status,
 		.get_plca_cfg	    = genphy_c45_plca_get_cfg,
-		.set_plca_cfg	    = genphy_c45_plca_set_cfg,
+		.set_plca_cfg	    = lan86xx_plca_set_cfg,
 		.get_plca_status    = genphy_c45_plca_get_status,
 	},
 	{
@@ -442,7 +478,7 @@ static struct phy_driver microchip_t1s_driver[] = {
 		.config_init        = lan867x_revc_config_init,
 		.read_status        = lan86xx_read_status,
 		.get_plca_cfg	    = genphy_c45_plca_get_cfg,
-		.set_plca_cfg	    = genphy_c45_plca_set_cfg,
+		.set_plca_cfg	    = lan86xx_plca_set_cfg,
 		.get_plca_status    = genphy_c45_plca_get_status,
 	},
 	{
@@ -454,7 +490,7 @@ static struct phy_driver microchip_t1s_driver[] = {
 		.read_mmd           = lan865x_phy_read_mmd,
 		.write_mmd          = lan865x_phy_write_mmd,
 		.get_plca_cfg	    = genphy_c45_plca_get_cfg,
-		.set_plca_cfg	    = genphy_c45_plca_set_cfg,
+		.set_plca_cfg	    = lan86xx_plca_set_cfg,
 		.get_plca_status    = genphy_c45_plca_get_status,
 	},
 };