[PATCH v2 net 1/2] net: enetc: restore RX ring congestion mode after ring reconfiguration

[wei.fang@oss.nxp.com]

From: Wei Fang <wei.fang@nxp.com>

The RX ring congestion mode (CM) is only configured in the phylink
.mac_link_up() callback enetc_pl_mac_link_up(), which sets the
ENETC_RBMR_CM bit when tx_pause is enabled. This callback runs only when
the link status changes.

However, enetc_reconfigure() tears down and re-creates the RX BD rings at
runtime without any link status change, for example when attaching or
detaching an XDP program, or when enabling/disabling PTP RX hardware
timestamping. The rings are rebuilt from a cleared RBMR, so the CM bit is
lost. Since the link status does not change, enetc_pl_mac_link_up() is
not called again and the CM bit is never restored.

As a result, the ENETC MAC can no longer generate PAUSE frames on ingress
congestion, and flow control stops working after such a reconfiguration.

Track the desired CM state in a software flag ENETC_RXBDR_CM. Set or clear
this flag in enetc_pl_mac_link_up() according to tx_pause. When the RX BD
rings are (re)enabled, enetc_enable_rxbdr() consults this flag and restores
the ENETC_RBMR_CM bit accordingly, so flow control survives ring
reconfiguration even when the link status does not change.

RBMR is now written as a whole word from enetc_enable_rxbdr() rather than
by read-modify-write from several call sites. Serialize the remaining RBMR
read-modify-write paths, the congestion mode update and the RX VLAN offload
update, with the new si->gen_lock so they cannot race each other.

Fixes: 5093406c784f ("net: enetc: implement ring reconfiguration procedure for PTP RX timestamping")
Signed-off-by: Wei Fang <wei.fang@nxp.com>
---
 drivers/net/ethernet/freescale/enetc/enetc.c  | 72 +++++++++++++++----
 drivers/net/ethernet/freescale/enetc/enetc.h  |  9 +++
 .../net/ethernet/freescale/enetc/enetc_pf.c   | 14 +---
 3 files changed, 68 insertions(+), 27 deletions(-)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
index 8e3f345dd9aa..80f0082f6c63 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc.c
@@ -81,6 +81,33 @@ void enetc_reset_mac_addr_filter(struct enetc_mac_filter *filter)
 }
 EXPORT_SYMBOL_GPL(enetc_reset_mac_addr_filter);
 
+void enetc_set_congestion_mode(struct enetc_ndev_priv *priv, bool enable)
+{
+	struct enetc_si *si = priv->si;
+	struct enetc_hw *hw = &si->hw;
+
+	spin_lock(&si->gen_lock);
+
+	if (enable)
+		set_bit(ENETC_RXBDR_CM, &priv->flags);
+	else
+		clear_bit(ENETC_RXBDR_CM, &priv->flags);
+
+	for (int i = 0; i < priv->num_rx_rings; i++) {
+		u32 old_rbmr = enetc_rxbdr_rd(hw, i, ENETC_RBMR);
+		u32 rbmr;
+
+		rbmr = u32_replace_bits(old_rbmr, enable, ENETC_RBMR_CM);
+		if (rbmr == old_rbmr)
+			continue;
+
+		enetc_rxbdr_wr(hw, i, ENETC_RBMR, rbmr);
+	}
+
+	spin_unlock(&si->gen_lock);
+}
+EXPORT_SYMBOL_GPL(enetc_set_congestion_mode);
+
 static int enetc_num_stack_tx_queues(struct enetc_ndev_priv *priv)
 {
 	int num_tx_rings = priv->num_tx_rings;
@@ -2632,7 +2659,6 @@ static void enetc_setup_rxbdr(struct enetc_hw *hw, struct enetc_bdr *rx_ring,
 			      bool extended)
 {
 	int idx = rx_ring->index;
-	u32 rbmr = 0;
 
 	enetc_rxbdr_wr(hw, idx, ENETC_RBBAR0,
 		       lower_32_bits(rx_ring->bd_dma_base));
@@ -2660,12 +2686,6 @@ static void enetc_setup_rxbdr(struct enetc_hw *hw, struct enetc_bdr *rx_ring,
 	enetc_rxbdr_wr(hw, idx, ENETC_RBICR0, ENETC_RBICR0_ICEN | 0x1);
 
 	rx_ring->ext_en = extended;
-	if (rx_ring->ext_en)
-		rbmr |= ENETC_RBMR_BDS;
-
-	if (rx_ring->ndev->features & NETIF_F_HW_VLAN_CTAG_RX)
-		rbmr |= ENETC_RBMR_VTE;
-
 	rx_ring->rcir = hw->reg + ENETC_BDR(RX, idx, ENETC_RBCIR);
 	rx_ring->idr = hw->reg + ENETC_SIRXIDR;
 
@@ -2676,8 +2696,6 @@ static void enetc_setup_rxbdr(struct enetc_hw *hw, struct enetc_bdr *rx_ring,
 	enetc_lock_mdio();
 	enetc_refill_rx_ring(rx_ring, enetc_bd_unused(rx_ring));
 	enetc_unlock_mdio();
-
-	enetc_rxbdr_wr(hw, idx, ENETC_RBMR, rbmr);
 }
 
 static void enetc_setup_bdrs(struct enetc_ndev_priv *priv, bool extended)
@@ -2704,21 +2722,34 @@ static void enetc_enable_txbdr(struct enetc_hw *hw, struct enetc_bdr *tx_ring)
 
 static void enetc_enable_rxbdr(struct enetc_hw *hw, struct enetc_bdr *rx_ring)
 {
+	struct enetc_ndev_priv *priv = netdev_priv(rx_ring->ndev);
 	int idx = rx_ring->index;
-	u32 rbmr;
+	u32 rbmr = ENETC_RBMR_EN;
+
+	if (rx_ring->ext_en)
+		rbmr |= ENETC_RBMR_BDS;
+
+	if (rx_ring->ndev->features & NETIF_F_HW_VLAN_CTAG_RX)
+		rbmr |= ENETC_RBMR_VTE;
+
+	if (test_bit(ENETC_RXBDR_CM, &priv->flags))
+		rbmr |= ENETC_RBMR_CM;
 
-	rbmr = enetc_rxbdr_rd(hw, idx, ENETC_RBMR);
-	rbmr |= ENETC_RBMR_EN;
 	enetc_rxbdr_wr(hw, idx, ENETC_RBMR, rbmr);
 }
 
 static void enetc_enable_rx_bdrs(struct enetc_ndev_priv *priv)
 {
-	struct enetc_hw *hw = &priv->si->hw;
+	struct enetc_si *si = priv->si;
+	struct enetc_hw *hw = &si->hw;
 	int i;
 
+	spin_lock(&si->gen_lock);
+
 	for (i = 0; i < priv->num_rx_rings; i++)
 		enetc_enable_rxbdr(hw, priv->rx_ring[i]);
+
+	spin_unlock(&si->gen_lock);
 }
 
 static void enetc_enable_tx_bdrs(struct enetc_ndev_priv *priv)
@@ -2748,11 +2779,16 @@ static void enetc_disable_txbdr(struct enetc_hw *hw, struct enetc_bdr *rx_ring)
 
 static void enetc_disable_rx_bdrs(struct enetc_ndev_priv *priv)
 {
-	struct enetc_hw *hw = &priv->si->hw;
+	struct enetc_si *si = priv->si;
+	struct enetc_hw *hw = &si->hw;
 	int i;
 
+	spin_lock(&si->gen_lock);
+
 	for (i = 0; i < priv->num_rx_rings; i++)
 		enetc_disable_rxbdr(hw, priv->rx_ring[i]);
+
+	spin_unlock(&si->gen_lock);
 }
 
 static void enetc_disable_tx_bdrs(struct enetc_ndev_priv *priv)
@@ -3344,11 +3380,16 @@ EXPORT_SYMBOL_GPL(enetc_get_stats);
 static void enetc_enable_rxvlan(struct net_device *ndev, bool en)
 {
 	struct enetc_ndev_priv *priv = netdev_priv(ndev);
-	struct enetc_hw *hw = &priv->si->hw;
+	struct enetc_si *si = priv->si;
+	struct enetc_hw *hw = &si->hw;
 	int i;
 
+	spin_lock(&si->gen_lock);
+
 	for (i = 0; i < priv->num_rx_rings; i++)
 		enetc_bdr_enable_rxvlan(hw, i, en);
+
+	spin_unlock(&si->gen_lock);
 }
 
 static void enetc_enable_txvlan(struct net_device *ndev, bool en)
@@ -3679,6 +3720,7 @@ int enetc_pci_probe(struct pci_dev *pdev, const char *name, int sizeof_priv)
 
 	si = PTR_ALIGN(p, ENETC_SI_ALIGN);
 	si->pad = (char *)si - (char *)p;
+	spin_lock_init(&si->gen_lock);
 
 	pci_set_drvdata(pdev, si);
 	si->pdev = pdev;
diff --git a/drivers/net/ethernet/freescale/enetc/enetc.h b/drivers/net/ethernet/freescale/enetc/enetc.h
index 8839cfb49bcf..d1e9d9130057 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc.h
+++ b/drivers/net/ethernet/freescale/enetc/enetc.h
@@ -309,6 +309,13 @@ struct enetc_si {
 
 	struct net_device *ndev; /* back ref. */
 
+	/* General-purpose lock serializing updates that must not race,
+	 * e.g. read-modify-write of shared hardware registers and of
+	 * selected priv->flags bits between the phylink link callbacks
+	 * and the ring (re)configuration path.
+	 */
+	spinlock_t gen_lock;
+
 	union {
 		struct enetc_cbdr cbd_ring; /* Only ENETC 1.0 */
 		struct ntmp_user ntmp_user; /* ENETC 4.1 and later */
@@ -417,6 +424,7 @@ enum enetc_active_offloads {
 enum enetc_flags_bit {
 	ENETC_TX_ONESTEP_TSTAMP_IN_PROGRESS = 0,
 	ENETC_TX_DOWN,
+	ENETC_RXBDR_CM,
 };
 
 /* interrupt coalescing modes */
@@ -505,6 +513,7 @@ int enetc_get_driver_data(struct enetc_si *si);
 void enetc_add_mac_addr_ht_filter(struct enetc_mac_filter *filter,
 				  const unsigned char *addr);
 void enetc_reset_mac_addr_filter(struct enetc_mac_filter *filter);
+void enetc_set_congestion_mode(struct enetc_ndev_priv *priv, bool enable);
 
 int enetc_open(struct net_device *ndev);
 int enetc_close(struct net_device *ndev);
diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pf.c b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
index a509929f89f2..55c07c528f22 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_pf.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
@@ -556,8 +556,7 @@ static void enetc_pl_mac_link_up(struct phylink_config *config,
 	struct enetc_hw *hw = &pf->si->hw;
 	struct enetc_si *si = pf->si;
 	struct enetc_ndev_priv *priv;
-	u32 rbmr, cmd_cfg;
-	int idx;
+	u32 cmd_cfg;
 
 	priv = netdev_priv(pf->si->ndev);
 
@@ -569,16 +568,7 @@ static void enetc_pl_mac_link_up(struct phylink_config *config,
 		enetc_force_rgmii_mac(si, speed, duplex);
 
 	/* Flow control */
-	for (idx = 0; idx < priv->num_rx_rings; idx++) {
-		rbmr = enetc_rxbdr_rd(hw, idx, ENETC_RBMR);
-
-		if (tx_pause)
-			rbmr |= ENETC_RBMR_CM;
-		else
-			rbmr &= ~ENETC_RBMR_CM;
-
-		enetc_rxbdr_wr(hw, idx, ENETC_RBMR, rbmr);
-	}
+	enetc_set_congestion_mode(priv, tx_pause);
 
 	if (tx_pause) {
 		/* When the port first enters congestion, send a PAUSE request
-- 
2.34.1