net: lan966x: Add offload support for cbs

Lan966x switch supports credit based shaper in hardware according to
IEEE Std 802.1Q-2018 Section 8.6.8.2. Add support for cbs configuration
on egress port of lan966x switch.
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/lan966x/Makefile

@@ -10,4 +10,4 @@ lan966x-switch-objs  := lan966x_main.o lan966x_phylink.o lan966x_port.o \
 			lan966x_vlan.o lan966x_fdb.o lan966x_mdb.o \
 			lan966x_ptp.o lan966x_fdma.o lan966x_lag.o \
 			lan966x_tc.o lan966x_mqprio.o lan966x_taprio.o \
-			lan966x_tbf.o
+			lan966x_tbf.o lan966x_cbs.o

drivers/net/ethernet/microchip/lan966x/lan966x_cbs.c

+// SPDX-License-Identifier: GPL-2.0+
+
+#include "lan966x_main.h"
+
+int lan966x_cbs_add(struct lan966x_port *port,
+		    struct tc_cbs_qopt_offload *qopt)
+{
+	struct lan966x *lan966x = port->lan966x;
+	u32 cir, cbs;
+	u8 se_idx;
+
+	/* Check for invalid values */
+	if (qopt->idleslope <= 0 ||
+	    qopt->sendslope >= 0 ||
+	    qopt->locredit >= qopt->hicredit)
+		return -EINVAL;
+
+	se_idx = SE_IDX_QUEUE + port->chip_port * NUM_PRIO_QUEUES + qopt->queue;
+	cir = qopt->idleslope;
+	cbs = (qopt->idleslope - qopt->sendslope) *
+		(qopt->hicredit - qopt->locredit) /
+		-qopt->sendslope;
+
+	/* Rate unit is 100 kbps */
+	cir = DIV_ROUND_UP(cir, 100);
+	/* Avoid using zero rate */
+	cir = cir ?: 1;
+	/* Burst unit is 4kB */
+	cbs = DIV_ROUND_UP(cbs, 4096);
+	/* Avoid using zero burst */
+	cbs = cbs ?: 1;
+
+	/* Check that actually the result can be written */
+	if (cir > GENMASK(15, 0) ||
+	    cbs > GENMASK(6, 0))
+		return -EINVAL;
+
+	lan_rmw(QSYS_SE_CFG_SE_AVB_ENA_SET(1) |
+		QSYS_SE_CFG_SE_FRM_MODE_SET(1),
+		QSYS_SE_CFG_SE_AVB_ENA |
+		QSYS_SE_CFG_SE_FRM_MODE,
+		lan966x, QSYS_SE_CFG(se_idx));
+
+	lan_wr(QSYS_CIR_CFG_CIR_RATE_SET(cir) |
+	       QSYS_CIR_CFG_CIR_BURST_SET(cbs),
+	       lan966x, QSYS_CIR_CFG(se_idx));
+
+	return 0;
+}
+
+int lan966x_cbs_del(struct lan966x_port *port,
+		    struct tc_cbs_qopt_offload *qopt)
+{
+	struct lan966x *lan966x = port->lan966x;
+	u8 se_idx;
+
+	se_idx = SE_IDX_QUEUE + port->chip_port * NUM_PRIO_QUEUES + qopt->queue;
+
+	lan_rmw(QSYS_SE_CFG_SE_AVB_ENA_SET(1) |
+		QSYS_SE_CFG_SE_FRM_MODE_SET(0),
+		QSYS_SE_CFG_SE_AVB_ENA |
+		QSYS_SE_CFG_SE_FRM_MODE,
+		lan966x, QSYS_SE_CFG(se_idx));
+
+	lan_wr(QSYS_CIR_CFG_CIR_RATE_SET(0) |
+	       QSYS_CIR_CFG_CIR_BURST_SET(0),
+	       lan966x, QSYS_CIR_CFG(se_idx));
+
+	return 0;
+}

drivers/net/ethernet/microchip/lan966x/lan966x_main.h

@@ -471,6 +471,11 @@ int lan966x_tbf_add(struct lan966x_port *port,
 int lan966x_tbf_del(struct lan966x_port *port,
 		    struct tc_tbf_qopt_offload *qopt);
 
+int lan966x_cbs_add(struct lan966x_port *port,
+		    struct tc_cbs_qopt_offload *qopt);
+int lan966x_cbs_del(struct lan966x_port *port,
+		    struct tc_cbs_qopt_offload *qopt);
+
 static inline void __iomem *lan_addr(void __iomem *base[],
 				     int id, int tinst, int tcnt,
 				     int gbase, int ginst,

drivers/net/ethernet/microchip/lan966x/lan966x_tc.c

@@ -37,6 +37,13 @@ static int lan966x_tc_setup_qdisc_tbf(struct lan966x_port *port,
 	return -EOPNOTSUPP;
 }
 
+static int lan966x_tc_setup_qdisc_cbs(struct lan966x_port *port,
+				      struct tc_cbs_qopt_offload *qopt)
+{
+	return qopt->enable ? lan966x_cbs_add(port, qopt) :
+			      lan966x_cbs_del(port, qopt);
+}
+
 int lan966x_tc_setup(struct net_device *dev, enum tc_setup_type type,
 		     void *type_data)
 {
@@ -49,6 +56,8 @@ int lan966x_tc_setup(struct net_device *dev, enum tc_setup_type type,
 		return lan966x_tc_setup_qdisc_taprio(port, type_data);
 	case TC_SETUP_QDISC_TBF:
 		return lan966x_tc_setup_qdisc_tbf(port, type_data);
+	case TC_SETUP_QDISC_CBS:
+		return lan966x_tc_setup_qdisc_cbs(port, type_data);
 	default:
 		return -EOPNOTSUPP;
 	}