Subject: [PATCH v6 net-next 13/15] net: dsa: netc: initialize buffer pool table and implement flow-control

From: Wei Fang <[email-masked]>
Date: Sat, 9 May 2026 18:29:52 +0800

The buffer pool is a quantity of memory available for buffering a group
of flows (e.g. frames having the same priority, frames received from the
same port), while waiting to be transmitted on a port. The buffer pool
tracks internal memory consumption with upper bound limits and optionally
a non-shared portion when associated with a shared buffer pool. Currently
the shared buffer pool is not supported, it will be added in the future.

For i.MX94, the switch has 4 ports and 8 buffer pools, so each port is
allocated two buffer pools. For frames with priorities of 0 to 3, they
will be mapped to the first buffer pool; For frames with priorities of
4 to 7, they will be mapped to the second buffer pool. Each buffer pool
has a flow control on threshold and a flow control off threshold. By
setting these threshold, add the flow control support to each port.

Signed-off-by: Wei Fang <[email-masked]>
---
 drivers/net/dsa/netc/netc_main.c      | 128 ++++++++++++++++++++++++++
 drivers/net/dsa/netc/netc_platform.c  |   2 +-
 drivers/net/dsa/netc/netc_switch.h    |  19 ++++
 drivers/net/dsa/netc/netc_switch_hw.h |  10 ++
 4 files changed, 158 insertions(+), 1 deletion(-)

diff --git a/drivers/net/dsa/netc/netc_main.c b/drivers/net/dsa/netc/netc_main.c
index 3229b7107add..43486b464c17 100644
--- a/drivers/net/dsa/netc/netc_main.c
+++ b/drivers/net/dsa/netc/netc_main.c
@@ -208,6 +208,9 @@ static void netc_get_switch_capabilities(struct netc_switch *priv)
 
 	val = netc_base_rd(regs, NETC_FDBHTCAPR);
 	priv->num_fdb_gmac = FIELD_GET(FDBHTCAPR_NUM_GMAC, val);
+
+	val = netc_base_rd(regs, NETC_BPCAPR);
+	priv->num_bp = FIELD_GET(BPCAPR_NUM_BP, val);
 }
 
 static int netc_init_all_ports(struct netc_switch *priv)
@@ -399,6 +402,15 @@ static void netc_port_fixed_config(struct netc_port *np)
 	/* Enable L2 and L3 DOS */
 	netc_port_rmw(np, NETC_PCR, PCR_L2DOSE | PCR_L3DOSE,
 		      PCR_L2DOSE | PCR_L3DOSE);
+
+	/* Set the quanta value of TX PAUSE frame */
+	netc_mac_port_wr(np, NETC_PM_PAUSE_QUANTA(0), NETC_PAUSE_QUANTA);
+
+	/* When a quanta timer counts down and reaches this value,
+	 * the MAC sends a refresh PAUSE frame with the programmed
+	 * full quanta value if a pause condition still exists.
+	 */
+	netc_mac_port_wr(np, NETC_PM_PAUSE_THRESH(0), NETC_PAUSE_THRESH);
 }
 
 static void netc_port_default_config(struct netc_port *np)
@@ -618,6 +630,77 @@ static int netc_add_standalone_fdb_bcast_entry(struct netc_switch *priv)
 				       bcast, NETC_STANDALONE_PVID);
 }
 
+static void netc_port_set_pbpmcr(struct netc_port *np, u64 mapping)
+{
+	u32 pbpmcr0 = lower_32_bits(mapping);
+	u32 pbpmcr1 = upper_32_bits(mapping);
+
+	netc_port_wr(np, NETC_PBPMCR0, pbpmcr0);
+	netc_port_wr(np, NETC_PBPMCR1, pbpmcr1);
+}
+
+static void netc_ipv_to_buffer_pool_mapping(struct netc_switch *priv)
+{
+	int bp_per_port = priv->num_bp / priv->info->num_ports;
+	int q = NETC_IPV_NUM / bp_per_port;
+	int r = NETC_IPV_NUM % bp_per_port;
+	int num = q + r;
+
+	/* IPV-to–buffer-pool mapping per port:
+	 * Each port is allocated 'bp_per_port' buffer pools and supports 8
+	 * IPVs, where a higher IPV indicates a higher frame priority. Each
+	 * IPV can be mapped to only one buffer pool.
+	 *
+	 * The mapping rule is as follows:
+	 * - The first 'num' IPVs share the port's first buffer pool (index
+	 * 'base_id').
+	 * - After that, every 'q' IPVs share one buffer pool, with pool
+	 * indices increasing sequentially.
+	 */
+	for (int i = 0; i < priv->info->num_ports; i++) {
+		u32 base_id = i * bp_per_port;
+		u32 bp_id = base_id;
+		u64 mapping = 0;
+
+		for (int ipv = 0; ipv < NETC_IPV_NUM; ipv++) {
+			/* Update the buffer pool index */
+			if (ipv >= num)
+				bp_id = base_id + ((ipv - num) / q) + 1;
+
+			mapping |= (u64)bp_id << (ipv * 8);
+		}
+
+		netc_port_set_pbpmcr(priv->ports[i], mapping);
+	}
+}
+
+static int netc_switch_bpt_default_config(struct netc_switch *priv)
+{
+	if (priv->num_bp < priv->info->num_ports)
+		return -EINVAL;
+
+	priv->bpt_list = devm_kcalloc(priv->dev, priv->num_bp,
+				      sizeof(struct bpt_cfge_data),
+				      GFP_KERNEL);
+	if (!priv->bpt_list)
+		return -ENOMEM;
+
+	/* Initialize the maximum threshold of each buffer pool entry */
+	for (int i = 0; i < priv->num_bp; i++) {
+		struct bpt_cfge_data *cfge = &priv->bpt_list[i];
+		int err;
+
+		cfge->max_thresh = cpu_to_le16(NETC_BP_THRESH);
+		err = ntmp_bpt_update_entry(&priv->ntmp, i, cfge);
+		if (err)
+			return err;
+	}
+
+	netc_ipv_to_buffer_pool_mapping(priv);
+
+	return 0;
+}
+
 static int netc_setup(struct dsa_switch *ds)
 {
 	struct netc_switch *priv = ds->priv;
@@ -647,6 +730,10 @@ static int netc_setup(struct dsa_switch *ds)
 	dsa_switch_for_each_available_port(dp, ds)
 		netc_port_default_config(priv->ports[dp->index]);
 
+	err = netc_switch_bpt_default_config(priv);
+	if (err)
+		goto free_lock_and_ntmp_user;
+
 	err = netc_add_standalone_vlan_entry(priv);
 	if (err)
 		goto free_lock_and_ntmp_user;
@@ -1196,6 +1283,45 @@ static void netc_port_set_rmii_mii_mac(struct netc_port *np,
 	netc_mac_port_rmw(np, NETC_PM_IF_MODE(0), mask, val);
 }
 
+static void netc_port_set_tx_pause(struct netc_port *np, bool tx_pause)
+{
+	struct netc_switch *priv = np->switch_priv;
+	int port = np->dp->index;
+	int i, j, num_bp;
+
+	num_bp = priv->num_bp / priv->info->num_ports;
+	for (i = 0, j = port * num_bp; i < num_bp; i++, j++) {
+		struct bpt_cfge_data *cfge = &priv->bpt_list[j];
+		struct bpt_cfge_data old_cfge = *cfge;
+
+		if (tx_pause) {
+			cfge->fc_on_thresh = cpu_to_le16(NETC_FC_THRESH_ON);
+			cfge->fc_off_thresh = cpu_to_le16(NETC_FC_THRESH_OFF);
+			cfge->fccfg_sbpen = FIELD_PREP(BPT_FC_CFG,
+						       BPT_FC_CFG_EN_BPFC);
+			cfge->fc_ports = cpu_to_le32(BIT(port));
+		} else {
+			cfge->fc_on_thresh = cpu_to_le16(0);
+			cfge->fc_off_thresh = cpu_to_le16(0);
+			cfge->fccfg_sbpen = 0;
+			cfge->fc_ports = cpu_to_le32(0);
+		}
+
+		if (ntmp_bpt_update_entry(&priv->ntmp, j, cfge)) {
+			*cfge = old_cfge;
+			dev_warn(priv->dev,
+				 "Failed to %s TX pause of buffer pool %d (swp%d)\n",
+				 tx_pause ? "enable" : "disable", j, port);
+		}
+	}
+}
+
+static void netc_port_set_rx_pause(struct netc_port *np, bool rx_pause)
+{
+	netc_mac_port_rmw(np, NETC_PM_CMD_CFG(0), PM_CMD_CFG_PAUSE_IGN,
+			  rx_pause ? 0 : PM_CMD_CFG_PAUSE_IGN);
+}
+
 static void netc_port_mac_rx_enable(struct netc_port *np)
 {
 	netc_port_rmw(np, NETC_POR, POR_RXDIS, 0);
@@ -1297,6 +1423,8 @@ static void netc_mac_link_up(struct phylink_config *config,
 	    interface == PHY_INTERFACE_MODE_MII)
 		netc_port_set_rmii_mii_mac(np, speed, duplex);
 
+	netc_port_set_tx_pause(np, tx_pause);
+	netc_port_set_rx_pause(np, rx_pause);
 	netc_port_mac_tx_enable(np);
 	netc_port_mac_rx_enable(np);
 }
diff --git a/drivers/net/dsa/netc/netc_platform.c b/drivers/net/dsa/netc/netc_platform.c
index bb4f92d238cb..34aeb6fceb3c 100644
--- a/drivers/net/dsa/netc/netc_platform.c
+++ b/drivers/net/dsa/netc/netc_platform.c
@@ -14,7 +14,7 @@ struct netc_switch_platform {
 static void imx94_switch_phylink_get_caps(int port,
 					  struct phylink_config *config)
 {
-	config->mac_capabilities = MAC_1000FD;
+	config->mac_capabilities = MAC_ASYM_PAUSE | MAC_SYM_PAUSE | MAC_1000FD;
 
 	switch (port) {
 	case 0 ... 1:
diff --git a/drivers/net/dsa/netc/netc_switch.h b/drivers/net/dsa/netc/netc_switch.h
index cc278a862623..4a9bf69907e9 100644
--- a/drivers/net/dsa/netc/netc_switch.h
+++ b/drivers/net/dsa/netc/netc_switch.h
@@ -28,11 +28,27 @@
 
 #define NETC_TC_NUM			8
 #define NETC_CBDR_NUM			2
+#define NETC_IPV_NUM			8
 
 #define NETC_MAX_FRAME_LEN		9600
 
 #define NETC_STANDALONE_PVID		0
 
+/* Threshold format: MANT (bits 11:4) * 2^EXP (bits 3:0)
+ * Unit: Memory words (average of 20 bytes each)
+ * NETC_BP_THRESH = 0x334, MANT = 0x33, EXP = 4. Threshold: 816 words
+ * NETC_FC_THRESH_ON = 0x533, MANT = 0x53, EXP = 3. Threshold: 664 words
+ * NETC_FC_THRESH_OFF = 0x3c3, MANT = 0x3c, EXP = 3. Threshold: 480 words
+ */
+#define NETC_BP_THRESH			0x334
+#define NETC_FC_THRESH_ON		0x533
+#define NETC_FC_THRESH_OFF		0x3c3
+
+/* PAUSE quanta: 0xFFFF = 65535 quanta (each quanta = 512 bit times) */
+#define NETC_PAUSE_QUANTA		0xFFFF
+/* PAUSE refresh threshold: send refresh when timer reaches this value */
+#define NETC_PAUSE_THRESH		0xFF00
+
 struct netc_switch;
 
 struct netc_switch_info {
@@ -94,6 +110,9 @@ struct netc_switch {
 
 	/* Switch hardware capabilities */
 	u32 num_fdb_gmac;
+	u32 num_bp;
+
+	struct bpt_cfge_data *bpt_list;
 };
 
 #define NETC_PRIV(ds)			((struct netc_switch *)((ds)->priv))
diff --git a/drivers/net/dsa/netc/netc_switch_hw.h b/drivers/net/dsa/netc/netc_switch_hw.h
index b04e9866d72a..caf5977c5100 100644
--- a/drivers/net/dsa/netc/netc_switch_hw.h
+++ b/drivers/net/dsa/netc/netc_switch_hw.h
@@ -12,6 +12,12 @@
 #define NETC_SWITCH_DEVICE_ID		0xeef2
 
 /* Definition of Switch base registers */
+#define NETC_BPCAPR			0x0008
+#define  BPCAPR_NUM_BP			GENMASK(7, 0)
+
+#define NETC_PBPMCR0			0x0400
+#define NETC_PBPMCR1			0x0404
+
 #define NETC_CBDRMR(a)			(0x0800 + (a) * 0x30)
 #define NETC_CBDRBAR0(a)		(0x0810 + (a) * 0x30)
 #define NETC_CBDRBAR1(a)		(0x0814 + (a) * 0x30)
@@ -141,6 +147,7 @@ enum netc_stg_stage {
 #define NETC_PM_CMD_CFG(a)		(0x1008 + (a) * 0x400)
 #define  PM_CMD_CFG_TX_EN		BIT(0)
 #define  PM_CMD_CFG_RX_EN		BIT(1)
+#define  PM_CMD_CFG_PAUSE_IGN		BIT(8)
 
 #define NETC_PM_MAXFRM(a)		(0x1014 + (a) * 0x400)
 #define  PM_MAXFRAM			GENMASK(15, 0)
@@ -149,6 +156,9 @@ enum netc_stg_stage {
 #define  PM_IEVENT_TX_EMPTY		BIT(5)
 #define  PM_IEVENT_RX_EMPTY		BIT(6)
 
+#define NETC_PM_PAUSE_QUANTA(a)		(0x1054 + (a) * 0x400)
+#define NETC_PM_PAUSE_THRESH(a)		(0x1064 + (a) * 0x400)
+
 #define NETC_PM_IF_MODE(a)		(0x1300 + (a) * 0x400)
 #define  PM_IF_MODE_IFMODE		GENMASK(2, 0)
 #define   IFMODE_MII			1
-- 
2.34.1