net: dsa: mt7530: always trap frames to active CPU port on MT7530

On the MT7530 switch, the CPU_PORT field indicates which CPU port to trap
frames to, regardless of the affinity of the inbound user port.

When multiple CPU ports are in use, if the DSA conduit interface is down,
trapped frames won't be passed to the conduit interface.

To make trapping frames work including this case, implement
ds->ops->conduit_state_change() on this subdriver and set the CPU_PORT
field to the numerically smallest CPU port whose conduit interface is up.
Introduce the active_cpu_ports field to store the information of the active
CPU ports. Correct the macros, CPU_PORT is bits 4 through 6 of the
register.

Add a comment to explain frame trapping for this switch.

Currently, the driver doesn't support the use of multiple CPU ports so this
is not necessarily a bug fix.
Suggested-by: Vladimir Oltean <olteanv@gmail.com>
Suggested-by: Russell King (Oracle) <linux@armlinux.org.uk>
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20240122-for-netnext-mt7530-improvements-1-v3-1-042401f2b279@arinc9.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/mt7530.c

@@ -1035,10 +1035,6 @@ mt753x_cpu_port_enable(struct dsa_switch *ds, int port)
 	mt7530_set(priv, MT7530_MFC, BC_FFP(BIT(port)) | UNM_FFP(BIT(port)) |
 		   UNU_FFP(BIT(port)));
 
-	/* Set CPU port number */
-	if (priv->id == ID_MT7530 || priv->id == ID_MT7621)
-		mt7530_rmw(priv, MT7530_MFC, CPU_MASK, CPU_EN | CPU_PORT(port));
-
 	/* Add the CPU port to the CPU port bitmap for MT7531 and the switch on
 	 * the MT7988 SoC. Trapped frames will be forwarded to the CPU port that
 	 * is affine to the inbound user port.
@@ -3093,6 +3089,36 @@ static int mt753x_set_mac_eee(struct dsa_switch *ds, int port,
 	return 0;
 }
 
+static void
+mt753x_conduit_state_change(struct dsa_switch *ds,
+			    const struct net_device *conduit,
+			    bool operational)
+{
+	struct dsa_port *cpu_dp = conduit->dsa_ptr;
+	struct mt7530_priv *priv = ds->priv;
+	int val = 0;
+	u8 mask;
+
+	/* Set the CPU port to trap frames to for MT7530. Trapped frames will be
+	 * forwarded to the numerically smallest CPU port whose conduit
+	 * interface is up.
+	 */
+	if (priv->id != ID_MT7530 && priv->id != ID_MT7621)
+		return;
+
+	mask = BIT(cpu_dp->index);
+
+	if (operational)
+		priv->active_cpu_ports |= mask;
+	else
+		priv->active_cpu_ports &= ~mask;
+
+	if (priv->active_cpu_ports)
+		val = CPU_EN | CPU_PORT(__ffs(priv->active_cpu_ports));
+
+	mt7530_rmw(priv, MT7530_MFC, CPU_EN | CPU_PORT_MASK, val);
+}
+
 static int mt7988_pad_setup(struct dsa_switch *ds, phy_interface_t interface)
 {
 	return 0;
@@ -3148,6 +3174,7 @@ const struct dsa_switch_ops mt7530_switch_ops = {
 	.phylink_mac_link_up	= mt753x_phylink_mac_link_up,
 	.get_mac_eee		= mt753x_get_mac_eee,
 	.set_mac_eee		= mt753x_set_mac_eee,
+	.conduit_state_change	= mt753x_conduit_state_change,
 };
 EXPORT_SYMBOL_GPL(mt7530_switch_ops);
 

drivers/net/dsa/mt7530.h

@@ -41,8 +41,8 @@ enum mt753x_id {
 #define  UNU_FFP(x)			(((x) & 0xff) << 8)
 #define  UNU_FFP_MASK			UNU_FFP(~0)
 #define  CPU_EN				BIT(7)
-#define  CPU_PORT(x)			((x) << 4)
-#define  CPU_MASK			(0xf << 4)
+#define  CPU_PORT_MASK			GENMASK(6, 4)
+#define  CPU_PORT(x)			FIELD_PREP(CPU_PORT_MASK, x)
 #define  MIRROR_EN			BIT(3)
 #define  MIRROR_PORT(x)			((x) & 0x7)
 #define  MIRROR_MASK			0x7
@@ -760,6 +760,7 @@ struct mt753x_info {
  * @irq_domain:		IRQ domain of the switch irq_chip
  * @irq_enable:		IRQ enable bits, synced to SYS_INT_EN
  * @create_sgmii:	Pointer to function creating SGMII PCS instance(s)
+ * @active_cpu_ports:	Holding the active CPU ports
  */
 struct mt7530_priv {
 	struct device		*dev;
@@ -786,6 +787,7 @@ struct mt7530_priv {
 	struct irq_domain *irq_domain;
 	u32 irq_enable;
 	int (*create_sgmii)(struct mt7530_priv *priv, bool dual_sgmii);
+	u8 active_cpu_ports;
 };
 
 struct mt7530_hw_vlan_entry {