enetc: add support Credit Based Shaper(CBS) for hardware offload

The ENETC hardware support the Credit Based Shaper(CBS) which part
of the IEEE-802.1Qav. The CBS driver was loaded by the sch_cbs
interface when set in the QOS in the kernel.

Here is an example command to set 20Mbits bandwidth in 1Gbits port
for taffic class 7:

tc qdisc add dev eth0 root handle 1: mqprio \
	   num_tc 8 map 0 1 2 3 4 5 6 7 hw 1

tc qdisc replace dev eth0 parent 1:8 cbs \
	   locredit -1470 hicredit 30 \
	   sendslope -980000 idleslope 20000 offload 1
Signed-off-by: Po Liu <Po.Liu@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/enetc/Kconfig

@@ -53,10 +53,10 @@ config FSL_ENETC_HW_TIMESTAMPING
 
 config FSL_ENETC_QOS
 	bool "ENETC hardware Time-sensitive Network support"
-	depends on (FSL_ENETC || FSL_ENETC_VF) && NET_SCH_TAPRIO
+	depends on (FSL_ENETC || FSL_ENETC_VF) && (NET_SCH_TAPRIO || NET_SCH_CBS)
 	help
 	  There are Time-Sensitive Network(TSN) capabilities(802.1Qbv/802.1Qci
 	  /802.1Qbu etc.) supported by ENETC. These TSN capabilities can be set
 	  enable/disable from user space via Qos commands(tc). In the kernel
 	  side, it can be loaded by Qos driver. Currently, it is only support
-	  taprio(802.1Qbv).
+	  taprio(802.1Qbv) and Credit Based Shaper(802.1Qbu).

drivers/net/ethernet/freescale/enetc/enetc.c

@@ -1496,6 +1496,8 @@ int enetc_setup_tc(struct net_device *ndev, enum tc_setup_type type,
 		return enetc_setup_tc_mqprio(ndev, type_data);
 	case TC_SETUP_QDISC_TAPRIO:
 		return enetc_setup_tc_taprio(ndev, type_data);
+	case TC_SETUP_QDISC_CBS:
+		return enetc_setup_tc_cbs(ndev, type_data);
 	default:
 		return -EOPNOTSUPP;
 	}

drivers/net/ethernet/freescale/enetc/enetc.h

@@ -255,7 +255,9 @@ int enetc_send_cmd(struct enetc_si *si, struct enetc_cbd *cbd);
 #ifdef CONFIG_FSL_ENETC_QOS
 int enetc_setup_tc_taprio(struct net_device *ndev, void *type_data);
 void enetc_sched_speed_set(struct net_device *ndev);
+int enetc_setup_tc_cbs(struct net_device *ndev, void *type_data);
 #else
 #define enetc_setup_tc_taprio(ndev, type_data) -EOPNOTSUPP
 #define enetc_sched_speed_set(ndev) (void)0
+#define enetc_setup_tc_cbs(ndev, type_data) -EOPNOTSUPP
 #endif

drivers/net/ethernet/freescale/enetc/enetc_hw.h

@@ -185,6 +185,8 @@ enum enetc_bdr_type {TX, RX};
 #define ENETC_PSICFGR0_SIVC(bmp)	(((bmp) & 0xff) << 24) /* VLAN_TYPE */
 
 #define ENETC_PTCCBSR0(n)	(0x1110 + (n) * 8) /* n = 0 to 7*/
+#define ENETC_CBSE		BIT(31)
+#define ENETC_CBS_BW_MASK	GENMASK(6, 0)
 #define ENETC_PTCCBSR1(n)	(0x1114 + (n) * 8) /* n = 0 to 7*/
 #define ENETC_RSSHASH_KEY_SIZE	40
 #define ENETC_PRSSK(n)		(0x1410 + (n) * 4) /* n = [0..9] */
@@ -603,6 +605,8 @@ struct enetc_cbd {
 	u8 status_flags;
 };
 
+#define ENETC_CLK  400000000ULL
+
 /* port time gating control register */
 #define ENETC_QBV_PTGCR_OFFSET		0x11a00
 #define ENETC_QBV_TGE			BIT(31)

drivers/net/ethernet/freescale/enetc/enetc_qos.c

@@ -4,6 +4,7 @@
 #include "enetc.h"
 
 #include <net/pkt_sched.h>
+#include <linux/math64.h>
 
 static u16 enetc_get_max_gcl_len(struct enetc_hw *hw)
 {
@@ -170,3 +171,130 @@ int enetc_setup_tc_taprio(struct net_device *ndev, void *type_data)
 
 	return err;
 }
+
+static u32 enetc_get_cbs_enable(struct enetc_hw *hw, u8 tc)
+{
+	return enetc_port_rd(hw, ENETC_PTCCBSR0(tc)) & ENETC_CBSE;
+}
+
+static u8 enetc_get_cbs_bw(struct enetc_hw *hw, u8 tc)
+{
+	return enetc_port_rd(hw, ENETC_PTCCBSR0(tc)) & ENETC_CBS_BW_MASK;
+}
+
+int enetc_setup_tc_cbs(struct net_device *ndev, void *type_data)
+{
+	struct enetc_ndev_priv *priv = netdev_priv(ndev);
+	struct tc_cbs_qopt_offload *cbs = type_data;
+	u32 port_transmit_rate = priv->speed;
+	u8 tc_nums = netdev_get_num_tc(ndev);
+	struct enetc_si *si = priv->si;
+	u32 hi_credit_bit, hi_credit_reg;
+	u32 max_interference_size;
+	u32 port_frame_max_size;
+	u32 tc_max_sized_frame;
+	u8 tc = cbs->queue;
+	u8 prio_top, prio_next;
+	int bw_sum = 0;
+	u8 bw;
+
+	prio_top = netdev_get_prio_tc_map(ndev, tc_nums - 1);
+	prio_next = netdev_get_prio_tc_map(ndev, tc_nums - 2);
+
+	/* Support highest prio and second prio tc in cbs mode */
+	if (tc != prio_top && tc != prio_next)
+		return -EOPNOTSUPP;
+
+	if (!cbs->enable) {
+		/* Make sure the other TC that are numerically
+		 * lower than this TC have been disabled.
+		 */
+		if (tc == prio_top &&
+		    enetc_get_cbs_enable(&si->hw, prio_next)) {
+			dev_err(&ndev->dev,
+				"Disable TC%d before disable TC%d\n",
+				prio_next, tc);
+			return -EINVAL;
+		}
+
+		enetc_port_wr(&si->hw, ENETC_PTCCBSR1(tc), 0);
+		enetc_port_wr(&si->hw, ENETC_PTCCBSR0(tc), 0);
+
+		return 0;
+	}
+
+	if (cbs->idleslope - cbs->sendslope != port_transmit_rate * 1000L ||
+	    cbs->idleslope < 0 || cbs->sendslope > 0)
+		return -EOPNOTSUPP;
+
+	port_frame_max_size = ndev->mtu + VLAN_ETH_HLEN + ETH_FCS_LEN;
+
+	bw = cbs->idleslope / (port_transmit_rate * 10UL);
+
+	/* Make sure the other TC that are numerically
+	 * higher than this TC have been enabled.
+	 */
+	if (tc == prio_next) {
+		if (!enetc_get_cbs_enable(&si->hw, prio_top)) {
+			dev_err(&ndev->dev,
+				"Enable TC%d first before enable TC%d\n",
+				prio_top, prio_next);
+			return -EINVAL;
+		}
+		bw_sum += enetc_get_cbs_bw(&si->hw, prio_top);
+	}
+
+	if (bw_sum + bw >= 100) {
+		dev_err(&ndev->dev,
+			"The sum of all CBS Bandwidth can't exceed 100\n");
+		return -EINVAL;
+	}
+
+	tc_max_sized_frame = enetc_port_rd(&si->hw, ENETC_PTCMSDUR(tc));
+
+	/* For top prio TC, the max_interfrence_size is maxSizedFrame.
+	 *
+	 * For next prio TC, the max_interfrence_size is calculated as below:
+	 *
+	 *      max_interference_size = M0 + Ma + Ra * M0 / (R0 - Ra)
+	 *
+	 *	- RA: idleSlope for AVB Class A
+	 *	- R0: port transmit rate
+	 *	- M0: maximum sized frame for the port
+	 *	- MA: maximum sized frame for AVB Class A
+	 */
+
+	if (tc == prio_top) {
+		max_interference_size = port_frame_max_size * 8;
+	} else {
+		u32 m0, ma, r0, ra;
+
+		m0 = port_frame_max_size * 8;
+		ma = enetc_port_rd(&si->hw, ENETC_PTCMSDUR(prio_top)) * 8;
+		ra = enetc_get_cbs_bw(&si->hw, prio_top) *
+			port_transmit_rate * 10000ULL;
+		r0 = port_transmit_rate * 1000000ULL;
+		max_interference_size = m0 + ma +
+			(u32)div_u64((u64)ra * m0, r0 - ra);
+	}
+
+	/* hiCredit bits calculate by:
+	 *
+	 * maxSizedFrame * (idleSlope/portTxRate)
+	 */
+	hi_credit_bit = max_interference_size * bw / 100;
+
+	/* hiCredit bits to hiCredit register need to calculated as:
+	 *
+	 * (enetClockFrequency / portTransmitRate) * 100
+	 */
+	hi_credit_reg = (u32)div_u64((ENETC_CLK * 100ULL) * hi_credit_bit,
+				     port_transmit_rate * 1000000ULL);
+
+	enetc_port_wr(&si->hw, ENETC_PTCCBSR1(tc), hi_credit_reg);
+
+	/* Set bw register and enable this traffic class */
+	enetc_port_wr(&si->hw, ENETC_PTCCBSR0(tc), bw | ENETC_CBSE);
+
+	return 0;
+}