net: dsa: microchip: ksz8795: add LINK_MD register support

Add mapping for LINK_MD register to enable cable testing functionality.
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/microchip/ksz8795.c

@@ -6,6 +6,7 @@
  *	Tristram Ha <Tristram.Ha@microchip.com>
  */
 
+#include <linux/bitfield.h>
 #include <linux/delay.h>
 #include <linux/export.h>
 #include <linux/gpio.h>
@@ -729,6 +730,7 @@ static void ksz8_r_phy(struct ksz_device *dev, u16 phy, u16 reg, u16 *val)
 	u8 restart, speed, ctrl, link;
 	const u8 *regs = ksz8->regs;
 	int processed = true;
+	u8 val1, val2;
 	u16 data = 0;
 	u8 p = phy;
 
@@ -816,6 +818,22 @@ static void ksz8_r_phy(struct ksz_device *dev, u16 phy, u16 reg, u16 *val)
 		if (data & ~LPA_SLCT)
 			data |= LPA_LPACK;
 		break;
+	case PHY_REG_LINK_MD:
+		ksz_pread8(dev, p, REG_PORT_LINK_MD_CTRL, &val1);
+		ksz_pread8(dev, p, REG_PORT_LINK_MD_RESULT, &val2);
+		if (val1 & PORT_START_CABLE_DIAG)
+			data |= PHY_START_CABLE_DIAG;
+
+		if (val1 & PORT_CABLE_10M_SHORT)
+			data |= PHY_CABLE_10M_SHORT;
+
+		data |= FIELD_PREP(PHY_CABLE_DIAG_RESULT_M,
+				FIELD_GET(PORT_CABLE_DIAG_RESULT_M, val1));
+
+		data |= FIELD_PREP(PHY_CABLE_FAULT_COUNTER_M,
+				(FIELD_GET(PORT_CABLE_FAULT_COUNTER_H, val1) << 8) |
+				FIELD_GET(PORT_CABLE_FAULT_COUNTER_L, val2));
+		break;
 	case PHY_REG_PHY_CTRL:
 		ksz_pread8(dev, p, regs[P_LINK_STATUS], &link);
 		if (link & PORT_MDIX_STATUS)
@@ -932,6 +950,10 @@ static void ksz8_w_phy(struct ksz_device *dev, u16 phy, u16 reg, u16 val)
 		if (data != ctrl)
 			ksz_pwrite8(dev, p, regs[P_LOCAL_CTRL], data);
 		break;
+	case PHY_REG_LINK_MD:
+		if (val & PHY_START_CABLE_DIAG)
+			ksz_port_cfg(dev, p, REG_PORT_LINK_MD_CTRL, PORT_START_CABLE_DIAG, true);
+		break;
 	default:
 		break;
 	}

drivers/net/dsa/microchip/ksz8795_reg.h

@@ -249,7 +249,7 @@
 #define REG_PORT_4_LINK_MD_CTRL		0x4A
 
 #define PORT_CABLE_10M_SHORT		BIT(7)
-#define PORT_CABLE_DIAG_RESULT_M	0x3
+#define PORT_CABLE_DIAG_RESULT_M	GENMASK(6, 5)
 #define PORT_CABLE_DIAG_RESULT_S	5
 #define PORT_CABLE_STAT_NORMAL		0
 #define PORT_CABLE_STAT_OPEN		1
@@ -753,13 +753,14 @@
 #define PHY_REG_LINK_MD			0x1D
 
 #define PHY_START_CABLE_DIAG		BIT(15)
+#define PHY_CABLE_DIAG_RESULT_M		GENMASK(14, 13)
 #define PHY_CABLE_DIAG_RESULT		0x6000
 #define PHY_CABLE_STAT_NORMAL		0x0000
 #define PHY_CABLE_STAT_OPEN		0x2000
 #define PHY_CABLE_STAT_SHORT		0x4000
 #define PHY_CABLE_STAT_FAILED		0x6000
 #define PHY_CABLE_10M_SHORT		BIT(12)
-#define PHY_CABLE_FAULT_COUNTER		0x01FF
+#define PHY_CABLE_FAULT_COUNTER_M	GENMASK(8, 0)
 
 #define PHY_REG_PHY_CTRL		0x1F