net: dsa: microchip: monitor potential faults in half-duplex mode

The errata DS80000754 recommends monitoring potential faults in
half-duplex mode for the KSZ9477 family.

half-duplex is not very common so I just added a critical message
when the fault conditions are detected. The switch can be expected
to be unable to communicate anymore in these states and a software
reset of the switch would be required which I did not implement.

Fixes: b987e98e ("dsa: add DSA switch driver for Microchip KSZ9477")
Signed-off-by: Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/microchip/ksz9477.c

@@ -427,6 +427,57 @@ void ksz9477_freeze_mib(struct ksz_device *dev, int port, bool freeze)
 	mutex_unlock(&p->mib.cnt_mutex);
 }
 
+int ksz9477_errata_monitor(struct ksz_device *dev, int port,
+			   u64 tx_late_col)
+{
+	u32 pmavbc;
+	u8 status;
+	u16 pqm;
+	int ret;
+
+	ret = ksz_pread8(dev, port, REG_PORT_STATUS_0, &status);
+	if (ret)
+		return ret;
+	if (!(FIELD_GET(PORT_INTF_SPEED_MASK, status) == PORT_INTF_SPEED_NONE) &&
+	    !(status & PORT_INTF_FULL_DUPLEX)) {
+		/* Errata DS80000754 recommends monitoring potential faults in
+		 * half-duplex mode. The switch might not be able to communicate anymore
+		 * in these states.
+		 * If you see this message, please read the errata-sheet for more information:
+		 * https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ9477S-Errata-DS80000754.pdf
+		 * To workaround this issue, half-duplex mode should be avoided.
+		 * A software reset could be implemented to recover from this state.
+		 */
+		dev_warn_once(dev->dev,
+			      "Half-duplex detected on port %d, transmission halt may occur\n",
+			      port);
+		if (tx_late_col != 0) {
+			/* Transmission halt with late collisions */
+			dev_crit_once(dev->dev,
+				      "TX late collisions detected, transmission may be halted on port %d\n",
+				      port);
+		}
+		ret = ksz_read8(dev, REG_SW_LUE_CTRL_0, &status);
+		if (ret)
+			return ret;
+		if (status & SW_VLAN_ENABLE) {
+			ret = ksz_pread16(dev, port, REG_PORT_QM_TX_CNT_0__4, &pqm);
+			if (ret)
+				return ret;
+			ret = ksz_read32(dev, REG_PMAVBC, &pmavbc);
+			if (ret)
+				return ret;
+			if ((FIELD_GET(PMAVBC_MASK, pmavbc) <= PMAVBC_MIN) ||
+			    (FIELD_GET(PORT_QM_TX_CNT_M, pqm) >= PORT_QM_TX_CNT_MAX)) {
+				/* Transmission halt with Half-Duplex and VLAN */
+				dev_crit_once(dev->dev,
+					      "resources out of limits, transmission may be halted\n");
+			}
+		}
+	}
+	return ret;
+}
+
 void ksz9477_port_init_cnt(struct ksz_device *dev, int port)
 {
 	struct ksz_port_mib *mib = &dev->ports[port].mib;

drivers/net/dsa/microchip/ksz9477.h

@@ -36,6 +36,8 @@ int ksz9477_port_mirror_add(struct ksz_device *dev, int port,
 			    bool ingress, struct netlink_ext_ack *extack);
 void ksz9477_port_mirror_del(struct ksz_device *dev, int port,
 			     struct dsa_mall_mirror_tc_entry *mirror);
+int ksz9477_errata_monitor(struct ksz_device *dev, int port,
+			   u64 tx_late_col);
 void ksz9477_get_caps(struct ksz_device *dev, int port,
 		      struct phylink_config *config);
 int ksz9477_fdb_dump(struct ksz_device *dev, int port,

drivers/net/dsa/microchip/ksz9477_reg.h

@@ -843,8 +843,8 @@
 
 #define REG_PORT_STATUS_0		0x0030
 
-#define PORT_INTF_SPEED_M		0x3
-#define PORT_INTF_SPEED_S		3
+#define PORT_INTF_SPEED_MASK		GENMASK(4, 3)
+#define PORT_INTF_SPEED_NONE		GENMASK(1, 0)
 #define PORT_INTF_FULL_DUPLEX		BIT(2)
 #define PORT_TX_FLOW_CTRL		BIT(1)
 #define PORT_RX_FLOW_CTRL		BIT(0)
@@ -1168,6 +1168,11 @@
 #define PORT_RMII_CLK_SEL		BIT(7)
 #define PORT_MII_SEL_EDGE		BIT(5)
 
+#define REG_PMAVBC			0x03AC
+
+#define PMAVBC_MASK			GENMASK(26, 16)
+#define PMAVBC_MIN			0x580
+
 /* 4 - MAC */
 #define REG_PORT_MAC_CTRL_0		0x0400
 
@@ -1495,6 +1500,7 @@
 
 #define PORT_QM_TX_CNT_USED_S		0
 #define PORT_QM_TX_CNT_M		(BIT(11) - 1)
+#define PORT_QM_TX_CNT_MAX		0x200
 
 #define REG_PORT_QM_TX_CNT_1__4		0x0A14
 

drivers/net/dsa/microchip/ksz_common.c

@@ -1382,6 +1382,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.tc_cbs_supported = true,
 		.ops = &ksz9477_dev_ops,
 		.phylink_mac_ops = &ksz9477_phylink_mac_ops,
+		.phy_errata_9477 = true,
 		.mib_names = ksz9477_mib_names,
 		.mib_cnt = ARRAY_SIZE(ksz9477_mib_names),
 		.reg_mib_cnt = MIB_COUNTER_NUM,
@@ -1416,6 +1417,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.num_ipms = 8,
 		.ops = &ksz9477_dev_ops,
 		.phylink_mac_ops = &ksz9477_phylink_mac_ops,
+		.phy_errata_9477 = true,
 		.mib_names = ksz9477_mib_names,
 		.mib_cnt = ARRAY_SIZE(ksz9477_mib_names),
 		.reg_mib_cnt = MIB_COUNTER_NUM,
@@ -1450,6 +1452,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.num_ipms = 8,
 		.ops = &ksz9477_dev_ops,
 		.phylink_mac_ops = &ksz9477_phylink_mac_ops,
+		.phy_errata_9477 = true,
 		.mib_names = ksz9477_mib_names,
 		.mib_cnt = ARRAY_SIZE(ksz9477_mib_names),
 		.reg_mib_cnt = MIB_COUNTER_NUM,
@@ -1540,6 +1543,7 @@ const struct ksz_chip_data ksz_switch_chips[] = {
 		.tc_cbs_supported = true,
 		.ops = &ksz9477_dev_ops,
 		.phylink_mac_ops = &ksz9477_phylink_mac_ops,
+		.phy_errata_9477 = true,
 		.mib_names = ksz9477_mib_names,
 		.mib_cnt = ARRAY_SIZE(ksz9477_mib_names),
 		.reg_mib_cnt = MIB_COUNTER_NUM,
@@ -1820,6 +1824,7 @@ void ksz_r_mib_stats64(struct ksz_device *dev, int port)
 	struct rtnl_link_stats64 *stats;
 	struct ksz_stats_raw *raw;
 	struct ksz_port_mib *mib;
+	int ret;
 
 	mib = &dev->ports[port].mib;
 	stats = &mib->stats64;
@@ -1861,6 +1866,12 @@ void ksz_r_mib_stats64(struct ksz_device *dev, int port)
 	pstats->rx_pause_frames = raw->rx_pause;
 
 	spin_unlock(&mib->stats64_lock);
+
+	if (dev->info->phy_errata_9477) {
+		ret = ksz9477_errata_monitor(dev, port, raw->tx_late_col);
+		if (ret)
+			dev_err(dev->dev, "Failed to monitor transmission halt\n");
+	}
 }
 
 void ksz88xx_r_mib_stats64(struct ksz_device *dev, int port)

drivers/net/dsa/microchip/ksz_common.h

@@ -66,6 +66,7 @@ struct ksz_chip_data {
 	bool tc_cbs_supported;
 	const struct ksz_dev_ops *ops;
 	const struct phylink_mac_ops *phylink_mac_ops;
+	bool phy_errata_9477;
 	bool ksz87xx_eee_link_erratum;
 	const struct ksz_mib_names *mib_names;
 	int mib_cnt;