[PATCH net-next 13/14] net: dsa: netc: initialize buffer bool table and implement flow-control

Wei Fang
2026-03-16T09:42:24Z

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 <wei.fang@nxp.com>
---
drivers/net/dsa/netc/netc_main.c | 130 ++++++++++++++++++++++++++
drivers/net/dsa/netc/netc_switch.h | 9 ++
drivers/net/dsa/netc/netc_switch_hw.h | 12 +++
3 files changed, 151 insertions(+)

diff --git a/drivers/net/dsa/netc/netc_main.c b/drivers/net/dsa/netc/netc_main.c
index fd952b507cbd..15dd8d89f66d 100644
--- a/drivers/net/dsa/netc/netc_main.c
+++ b/drivers/net/dsa/netc/netc_main.c
@@ -402,6 +402,8 @@ static void netc_port_set_mlo(struct netc_port *np, enum netc_mlo mlo)

static void netc_port_fixed_config(struct netc_port *np)
{
+ u32 pqnt = 0xffff, qth = 0xff00;
+
/* Default IPV and DR setting */
netc_port_rmw(np, NETC_PQOSMR, PQOSMR_VS | PQOSMR_VE,
PQOSMR_VS | PQOSMR_VE);
@@ -409,6 +411,15 @@ 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), pqnt);
+
+ /* 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_TRHESH(0), qth);
}

static void netc_port_default_config(struct netc_port *np)
@@ -640,6 +651,77 @@ static int netc_add_standalone_fdb_bcast_entry(struct netc_switch *priv)
bcast, NETC_STANDALONE_PVID);
}

+static u32 netc_get_buffer_pool_num(struct netc_switch *priv)
+{
+ return netc_base_rd(&priv->regs, NETC_BPCAPR) & BPCAPR_NUM_BP;
+}
+
+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 num_port_bp = priv->num_bp / priv->info->num_ports;
+ int q = NETC_IPV_NUM / num_port_bp;
+ int r = NETC_IPV_NUM % num_port_bp;
+ int num = q + r;
+
+ /* IPV-to–buffer-pool mapping per port:
+ * Each port is allocated `num_port_bp` 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 * num_port_bp;
+ 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)
+{
+ priv->num_bp = netc_get_buffer_pool_num(priv);
+ 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];
+
+ cfge->max_thresh = cpu_to_le16(NETC_BP_THRESH);
+ ntmp_bpt_update_entry(&priv->ntmp, i, cfge);
+ }
+
+ netc_ipv_to_buffer_pool_mapping(priv);
+
+ return 0;
+}
+
static int netc_setup(struct dsa_switch *ds)
{
struct netc_switch *priv = ds->priv;
@@ -667,6 +749,10 @@ 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_ntmp_user;
+
err = netc_add_standalone_vlan_entry(priv);
if (err)
goto free_ntmp_user;
@@ -1241,6 +1327,40 @@ static void netc_port_set_hd_flow_control(struct netc_port *np, bool en)
en ? PM_CMD_CFG_HD_FCEN : 0);
}

+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;
+
+ cfge = &priv->bpt_list[j];
+ 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);
+ }
+
+ ntmp_bpt_update_entry(&priv->ntmp, j, cfge);
+ }
+}
+
+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, PCR_RXDIS, 0);
@@ -1305,7 +1425,17 @@ static void netc_mac_link_up(struct phylink_config *config,
net_port_set_rmii_mii_mac(np, speed, duplex);
}

+ if (duplex == DUPLEX_HALF) {
+ /* As per 802.3 annex 31B, PAUSE frames are only supported
+ * when the link is configured for full duplex operation.
+ */
+ tx_pause = false;
+ rx_pause = false;
+ }
+
netc_port_set_hd_flow_control(np, duplex == DUPLEX_HALF);
+ netc_port_set_tx_pause(np, tx_pause);
+ netc_port_set_rx_pause(np, rx_pause);
netc_port_mac_rx_enable(np);
}

diff --git a/drivers/net/dsa/netc/netc_switch.h b/drivers/net/dsa/netc/netc_switch.h
index 4b229a71578e..7ebffb136b2f 100644
--- a/drivers/net/dsa/netc/netc_switch.h
+++ b/drivers/net/dsa/netc/netc_switch.h
@@ -32,6 +32,12 @@

#define NETC_STANDALONE_PVID 0

+#define NETC_IPV_NUM 8
+/* MANT = bits 11:4, EXP = bits 3:0, threshold = MANT * 2 ^ EXP */
+#define NETC_BP_THRESH 0x334
+#define NETC_FC_THRESH_ON 0x533
+#define NETC_FC_THRESH_OFF 0x3c3
+
struct netc_switch;

struct netc_switch_info {
@@ -90,6 +96,9 @@ struct netc_switch {
struct ntmp_user ntmp;
struct hlist_head fdb_list;
struct mutex fdbt_lock; /* FDB table lock */
+
+ 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 a2b0c1a712f8..7ef870fbba4d 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)
@@ -163,6 +169,12 @@ enum netc_stg_stage {
#define NETC_PM_IEVENT(a) (0x1040 + (a) * 0x400)
#define PM_IEVENT_RX_EMPTY BIT(6)

+#define NETC_PM_PAUSE_QUANTA(a) (0x1054 + (a) * 0x400)
+#define PAUSE_QUANTA_PQNT GENMASK(15, 0)
+
+#define NETC_PM_PAUSE_TRHESH(a) (0x1064 + (a) * 0x400)
+#define PAUSE_TRHESH_QTH GENMASK(15, 0)
+
#define NETC_PM_IF_MODE(a) (0x1300 + (a) * 0x400)
#define PM_IF_MODE_IFMODE GENMASK(2, 0)
#define IFMODE_MII 1
--
2.34.1