net: ti: icssg-prueth: Add support for half duplex operation

This patch adds support for half duplex operation at 10M and 100M link
speeds for AM654x/AM64x devices.
- Driver configures rand_seed, a random number, in DMEM HD_RAND_SEED_OFFSET
field, which will be used by firmware for Back off time calculation.
- Driver informs FW about half duplex link operation in DMEM
PORT_LINK_SPEED_OFFSET field by setting bit 7 for 10/100M HD.

Hence, the half duplex operation depends on board design the
"ti,half-duplex-capable" property has to be enabled for ICSS-G ports if HW
is capable to perform half duplex.
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/icssg/icssg_config.c

@@ -433,6 +433,17 @@ int emac_set_port_state(struct prueth_emac *emac,
 	return ret;
 }
 
+void icssg_config_half_duplex(struct prueth_emac *emac)
+{
+	u32 val;
+
+	if (!emac->half_duplex)
+		return;
+
+	val = get_random_u32();
+	writel(val, emac->dram.va + HD_RAND_SEED_OFFSET);
+}
+
 void icssg_config_set_speed(struct prueth_emac *emac)
 {
 	u8 fw_speed;
@@ -453,5 +464,8 @@ void icssg_config_set_speed(struct prueth_emac *emac)
 		return;
 	}
 
+	if (emac->duplex == DUPLEX_HALF)
+		fw_speed |= FW_LINK_SPEED_HD;
+
 	writeb(fw_speed, emac->dram.va + PORT_LINK_SPEED_OFFSET);
 }

drivers/net/ethernet/ti/icssg/icssg_prueth.c

@@ -1029,6 +1029,8 @@ static void emac_adjust_link(struct net_device *ndev)
 		 * values
 		 */
 		if (emac->link) {
+			if (emac->duplex == DUPLEX_HALF)
+				icssg_config_half_duplex(emac);
 			/* Set the RGMII cfg for gig en and full duplex */
 			icssg_update_rgmii_cfg(prueth->miig_rt, emac);
 
@@ -1147,9 +1149,13 @@ static int emac_phy_connect(struct prueth_emac *emac)
 		return -ENODEV;
 	}
 
-	/* remove unsupported modes */
+	if (!emac->half_duplex) {
+		dev_dbg(prueth->dev, "half duplex mode is not supported\n");
 		phy_remove_link_mode(ndev->phydev, ETHTOOL_LINK_MODE_10baseT_Half_BIT);
 		phy_remove_link_mode(ndev->phydev, ETHTOOL_LINK_MODE_100baseT_Half_BIT);
+	}
+
+	/* remove unsupported modes */
 	phy_remove_link_mode(ndev->phydev, ETHTOOL_LINK_MODE_1000baseT_Half_BIT);
 	phy_remove_link_mode(ndev->phydev, ETHTOOL_LINK_MODE_Pause_BIT);
 	phy_remove_link_mode(ndev->phydev, ETHTOOL_LINK_MODE_Asym_Pause_BIT);
@@ -2113,6 +2119,10 @@ static int prueth_probe(struct platform_device *pdev)
 				      eth0_node->name);
 			goto exit_iep;
 		}
+
+		if (of_find_property(eth0_node, "ti,half-duplex-capable", NULL))
+			prueth->emac[PRUETH_MAC0]->half_duplex = 1;
+
 		prueth->emac[PRUETH_MAC0]->iep = prueth->iep0;
 	}
 
@@ -2124,6 +2134,9 @@ static int prueth_probe(struct platform_device *pdev)
 			goto netdev_exit;
 		}
 
+		if (of_find_property(eth1_node, "ti,half-duplex-capable", NULL))
+			prueth->emac[PRUETH_MAC1]->half_duplex = 1;
+
 		prueth->emac[PRUETH_MAC1]->iep = prueth->iep0;
 	}
 

drivers/net/ethernet/ti/icssg/icssg_prueth.h

@@ -145,6 +145,7 @@ struct prueth_emac {
 	struct icss_iep *iep;
 	unsigned int rx_ts_enabled : 1;
 	unsigned int tx_ts_enabled : 1;
+	unsigned int half_duplex : 1;
 
 	/* DMA related */
 	struct prueth_tx_chn tx_chns[PRUETH_MAX_TX_QUEUES];
@@ -271,6 +272,7 @@ int icssg_config(struct prueth *prueth, struct prueth_emac *emac,
 int emac_set_port_state(struct prueth_emac *emac,
 			enum icssg_port_state_cmd state);
 void icssg_config_set_speed(struct prueth_emac *emac);
+void icssg_config_half_duplex(struct prueth_emac *emac);
 
 /* Buffer queue helpers */
 int icssg_queue_pop(struct prueth *prueth, u8 queue);