Re: [PATCH net-next v8 09/10] net: airoha: Introduce WAN device flag

[...]

[ ... ]

quoted

+static int airoha_dev_init(struct net_device *netdev)
+{
+	struct airoha_gdm_dev *dev = netdev_priv(netdev);
+	struct airoha_gdm_port *port = dev->port;
 
 	switch (port->id) {
 	case AIROHA_GDM3_IDX:
+	case AIROHA_GDM4_IDX: {
+		struct airoha_eth *eth = dev->eth;
 
+		/* GDM2 supports a single net_device */
+		if (eth->ports[1] && eth->ports[1]->devs[0])
+			break;

Is there a strict probe-order dependency for these interfaces?

If GDM3 or GDM4 is probed before GDM2, eth->ports[1]->devs[0] will be NULL.
This leads GDM3/GDM4 to assume GDM2 is inactive, take the WAN role, and force
GDM2 into loopback mode.

Later, when GDM2 initializes:

quoted

+	case AIROHA_GDM2_IDX:
+		/* GDM2 is always used as wan */
+		dev->flags |= AIROHA_PRIV_F_WAN;
 		break;

It unconditionally assigns itself the WAN role.

Does this probe ordering create multiple WAN devices and leave GDM2's
hardware silently misconfigured since its routing capabilities were disabled
by GDM3's loopback configuration?

This is not a real issue since GDM2 is always registered before GDM3/GDM4.

quoted

 	default:
 		break;
 	}
 
+	airoha_dev_set_qdma(dev);
+	airoha_set_macaddr(dev, netdev->dev_addr);

When setting the MAC address, airoha_set_macaddr() does the following:

static void airoha_set_macaddr(struct airoha_gdm_dev *dev, const u8 *addr)
{
	...
	reg = airoha_is_lan_gdm_dev(dev) ? REG_FE_LAN_MAC_H : REG_FE_WAN_MAC_H;
	...
	airoha_fe_wr(eth, reg, val);
}

Since REG_FE_LAN_MAC_H is a global forwarding engine register rather than
per-port, will initializing subsequent LAN devices overwrite the hardware
MAC filter configured by the first LAN device?

Might this cause the hardware to drop packets for LAN interfaces that do not
match the single overwritten MAC address?

(Note: This was observed to be fixed later in the series by commit "net:
airoha: Support multiple LAN/WAN interfaces for hw MAC address configuration",
but is mentioned here as it appears to introduce a regression in this commit.)

As pointed out here, this is resolved in a subsequent patch in the series.

Regards,
Lorenzo

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260519-airoha-eth-multi-serdes-v8-0-6bd70e329df6@kernel.org?part=9