[PATCH 4.19 095/113] net: macb: Change interrupt and napi enable order in open

From: Greg Kroah-Hartman
Date: Wed May 15 2019 - 07:47:15 EST

From: Harini Katakam <harini.katakam@xxxxxxxxxx>

[ Upstream commit 0504453139ef5a593c9587e1e851febee859c7d8 ]

Current order in open:
-> Enable interrupts (macb_init_hw)
-> Enable NAPI
-> Start PHY

Sequence of RX handling:
-> RX interrupt occurs
-> Interrupt is cleared and interrupt bits disabled in handler
-> NAPI is scheduled
-> In NAPI, RX budget is processed and RX interrupts are re-enabled

With the above, on QEMU or fixed link setups (where PHY state doesn't
matter), there's a chance macb RX interrupt occurs before NAPI is
enabled. This will result in NAPI being scheduled before it is enabled.
Fix this macb open by changing the order.

Fixes: ae1f2a56d273 ("net: macb: Added support for many RX queues")
Signed-off-by: Harini Katakam <harini.katakam@xxxxxxxxxx>
Acked-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
drivers/net/ethernet/cadence/macb_main.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -2419,12 +2419,12 @@ static int macb_open(struct net_device *
return err;

- bp->macbgem_ops.mog_init_rings(bp);
- macb_init_hw(bp);
for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue)

+ bp->macbgem_ops.mog_init_rings(bp);
+ macb_init_hw(bp);
/* schedule a link state check */