net: ethernet: ti: am65-cpsw: enable DSCP to priority map for RX

AM65 CPSW hardware can map the 6-bit DSCP/TOS field to
appropriate priority queue via DSCP to Priority mapping registers
(CPSW_PN_RX_PRI_MAP_REG).

Use a default DSCP to User Priority (UP) mapping as per
https://datatracker.ietf.org/doc/html/rfc8325#section-4.3
and
https://datatracker.ietf.org/doc/html/rfc8622#section-11

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: rogerq

drivers/net/ethernet/ti/am65-cpsw-nuss.c

@@ -71,6 +71,8 @@
 #define AM65_CPSW_PORT_REG_RX_PRI_MAP		0x020
 #define AM65_CPSW_PORT_REG_RX_MAXLEN		0x024
 
+#define AM65_CPSW_PORTN_REG_CTL			0x004
+#define AM65_CPSW_PORTN_REG_DSCP_MAP		0x120
 #define AM65_CPSW_PORTN_REG_SA_L		0x308
 #define AM65_CPSW_PORTN_REG_SA_H		0x30c
 #define AM65_CPSW_PORTN_REG_TS_CTL              0x310
@@ -94,6 +96,10 @@
 /* AM65_CPSW_PORT_REG_PRI_CTL */
 #define AM65_CPSW_PORT_REG_PRI_CTL_RX_PTYPE_RROBIN	BIT(8)
 
+/* AM65_CPSW_PN_REG_CTL */
+#define AM65_CPSW_PN_REG_CTL_DSCP_IPV4_EN	BIT(1)
+#define AM65_CPSW_PN_REG_CTL_DSCP_IPV6_EN	BIT(2)
+
 /* AM65_CPSW_PN_TS_CTL register fields */
 #define AM65_CPSW_PN_TS_CTL_TX_ANX_F_EN		BIT(4)
 #define AM65_CPSW_PN_TS_CTL_TX_VLAN_LT1_EN	BIT(5)
@@ -176,6 +182,99 @@ static void am65_cpsw_port_set_sl_mac(struct am65_cpsw_port *slave,
 	writel(mac_lo, slave->port_base + AM65_CPSW_PORTN_REG_SA_L);
 }
 
+#define AM65_CPSW_DSCP_MAX	GENMASK(5, 0)
+#define AM65_CPSW_PRI_MAX	GENMASK(2, 0)
+#define AM65_CPSW_DSCP_PRI_PER_REG	8
+#define AM65_CPSW_DSCP_PRI_SIZE		4	/* in bits */
+static int am65_cpsw_port_set_dscp_map(struct am65_cpsw_port *slave, u8 dscp, u8 pri)
+{
+	int reg_ofs;
+	int bit_ofs;
+	u32 val;
+
+	if (dscp > AM65_CPSW_DSCP_MAX)
+		return -EINVAL;
+
+	if (pri > AM65_CPSW_PRI_MAX)
+		return -EINVAL;
+
+	/* 32-bit register offset to this dscp */
+	reg_ofs = (dscp / AM65_CPSW_DSCP_PRI_PER_REG) * 4;
+	/* bit field offset to this dscp */
+	bit_ofs = AM65_CPSW_DSCP_PRI_SIZE * (dscp % AM65_CPSW_DSCP_PRI_PER_REG);
+
+	val = readl(slave->port_base + AM65_CPSW_PORTN_REG_DSCP_MAP + reg_ofs);
+	val &= ~(AM65_CPSW_PRI_MAX << bit_ofs);	/* clear */
+	val |= pri << bit_ofs;			/* set */
+	writel(val, slave->port_base + AM65_CPSW_PORTN_REG_DSCP_MAP + reg_ofs);
+
+	return 0;
+}
+
+static void am65_cpsw_port_enable_dscp_map(struct am65_cpsw_port *slave)
+{
+	int dscp, pri;
+	u32 val;
+
+	/* Default DSCP to User Priority mapping as per:
+	 * https://datatracker.ietf.org/doc/html/rfc8325#section-4.3
+	 * and
+	 * https://datatracker.ietf.org/doc/html/rfc8622#section-11
+	 */
+	for (dscp = 0; dscp <= AM65_CPSW_DSCP_MAX; dscp++) {
+		switch (dscp) {
+		case 56:	/* CS7 */
+		case 48:	/* CS6 */
+			pri = 7;
+			break;
+		case 46:	/* EF */
+		case 44:	/* VA */
+			pri = 6;
+			break;
+		case 40:	/* CS5 */
+			pri = 5;
+			break;
+		case 34:	/* AF41 */
+		case 36:	/* AF42 */
+		case 38:	/* AF43 */
+		case 32:	/* CS4 */
+		case 26:	/* AF31 */
+		case 28:	/* AF32 */
+		case 30:	/* AF33 */
+		case 24:	/* CS3 */
+			pri = 4;
+			break;
+		case 18:	/* AF21 */
+		case 20:	/* AF22 */
+		case 22:	/* AF23 */
+			pri = 3;
+			break;
+		case 16:	/* CS2 */
+		case 10:	/* AF11 */
+		case 12:	/* AF12 */
+		case 14:	/* AF13 */
+		case 0:		/* DF */
+			pri = 0;
+			break;
+		case 8:		/* CS1 */
+		case 1:		/* LE */
+			pri = 1;
+			break;
+		default:
+			pri = 0;
+			break;
+		}
+
+		am65_cpsw_port_set_dscp_map(slave, dscp, pri);
+	}
+
+	/* enable port IPV4 and IPV6 DSCP for this port */
+	val = readl(slave->port_base + AM65_CPSW_PORTN_REG_CTL);
+	val |= AM65_CPSW_PN_REG_CTL_DSCP_IPV4_EN |
+		AM65_CPSW_PN_REG_CTL_DSCP_IPV6_EN;
+	writel(val, slave->port_base + AM65_CPSW_PORTN_REG_CTL);
+}
+
 static void am65_cpsw_sl_ctl_reset(struct am65_cpsw_port *port)
 {
 	cpsw_sl_reset(port->slave.mac_sl, 100);
@@ -916,6 +1015,7 @@ static int am65_cpsw_nuss_ndo_slave_open(struct net_device *ndev)
 	common->usage_count++;
 
 	am65_cpsw_port_set_sl_mac(port, ndev->dev_addr);
+	am65_cpsw_port_enable_dscp_map(port);
 
 	if (common->is_emac_mode)
 		am65_cpsw_init_port_emac_ale(port);