[PATCH net] net: bgmac: enable interrupts only after NAPI is ready

[Rosen Penev <rosenp@gmail.com>]

bgmac_open() calls bgmac_chip_init(), which unmasks the interrupts and
enables the MAC receiver, before request_irq() and napi_enable().
bgmac_enet_resume() also enables NAPI only after bgmac_chip_init().

When frames arrive in that window, the first RX interrupt masks all
interrupts in bgmac_interrupt() and calls napi_schedule() on a NAPI
instance that is still disabled, so nothing is scheduled. Nothing
unmasks the interrupts again, the RX ring fills up and the interface
stays deaf until it is brought down and up without traffic.

On an Asus RT-N16 (BCM4716) a single "ip link set eth0 down/up" while
a host sends UDP to the router left INT_MASK at 0, INT_STATUS with RX
pending and the RX DMA idle on a full ring, with the RX packet and
interrupt counters no longer moving. With this change, 10 of 10 such
cycles recovered on their own.

Request the IRQ and enable NAPI before the chip is initialized.

Fixes: dd4544f05469 ("bgmac: driver for GBit MAC core on BCMA bus")
Fixes: f3537b3494c0 ("net: ethernet: bgmac: driver power manangement")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/net/ethernet/broadcom/bgmac.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c
index 427a096e5ad4..20df9c8ab055 100644
--- a/drivers/net/ethernet/broadcom/bgmac.c
+++ b/drivers/net/ethernet/broadcom/bgmac.c
@@ -1183,9 +1183,6 @@ static int bgmac_open(struct net_device *net_dev)
 	if (err)
 		return err;
 
-	/* Specs say about reclaiming rings here, but we do that in DMA init */
-	bgmac_chip_init(bgmac);
-
 	err = request_irq(bgmac->irq, bgmac_interrupt, IRQF_SHARED,
 			  net_dev->name, net_dev);
 	if (err < 0) {
@@ -1195,6 +1192,9 @@ static int bgmac_open(struct net_device *net_dev)
 	}
 	napi_enable(&bgmac->napi);
 
+	/* Specs say about reclaiming rings here, but we do that in DMA init */
+	bgmac_chip_init(bgmac);
+
 	phy_start(net_dev->phydev);
 
 	netif_start_queue(net_dev);
@@ -1608,10 +1608,10 @@ int bgmac_enet_resume(struct bgmac *bgmac)
 	if (rc)
 		return rc;
 
-	bgmac_chip_init(bgmac);
-
 	napi_enable(&bgmac->napi);
 
+	bgmac_chip_init(bgmac);
+
 	netif_tx_lock(bgmac->net_dev);
 	netif_device_attach(bgmac->net_dev);
 	netif_tx_unlock(bgmac->net_dev);
-- 
2.56.0