[PATCH net 1/2] net: cpsw: unregister secondary netdev on probe failure

[Karl Mehltretter <kmehltretter@gmail.com>]

The legacy CPSW driver registers both netdevs in dual-EMAC mode before
requesting its IRQs. If a later IRQ request fails, the probe error path
unregisters only the primary netdev. Driver-core devres cleanup then calls
free_netdev() for the still-registered secondary netdev, triggering the
reg_state BUG_ON.

Track successful secondary registration and unregister that netdev before
the primary on this error path. The pointer cannot indicate registration:
cpsw_probe_dual_emac() sets cpsw->slaves[1].ndev before it calls
register_netdev().

Reproduced with QEMU fault injection by forcing the TX IRQ request to fail
with -EBUSY in dual-EMAC mode; real hardware was not tested.

Fixes: 070f9c658a59 ("net: ethernet: ti: cpsw: Push the request_irq function to the end of probe")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
 drivers/net/ethernet/ti/cpsw.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
index aa3531e844e8..4fc59f9f23fc 100644
--- a/drivers/net/ethernet/ti/cpsw.c
+++ b/drivers/net/ethernet/ti/cpsw.c
@@ -1550,6 +1550,7 @@ static int cpsw_probe(struct platform_device *pdev)
 	struct gpio_descs		*mode;
 	const struct soc_device_attribute *soc;
 	struct cpsw_common		*cpsw;
+	bool secondary_registered = false;
 	int ret = 0, ch;
 	int irq;
 
@@ -1717,6 +1718,7 @@ static int cpsw_probe(struct platform_device *pdev)
 			cpsw_err(priv, probe, "error probe slave 2 emac interface\n");
 			goto clean_unregister_netdev_ret;
 		}
+		secondary_registered = true;
 	}
 
 	/* Grab RX and TX IRQs. Note that we also have RX_THRESHOLD and
@@ -1764,6 +1766,8 @@ static int cpsw_probe(struct platform_device *pdev)
 	return 0;
 
 clean_unregister_netdev_ret:
+	if (secondary_registered)
+		unregister_netdev(cpsw->slaves[1].ndev);
 	unregister_netdev(ndev);
 clean_cpts:
 	cpts_release(cpsw->cpts);
-- 
2.53.0