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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Harini Katakam <harini.katakam@xilinx.com>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.19 095/113] net: macb: Change interrupt and napi enable order in open
Date:   Wed, 15 May 2019 12:56:26 +0200
Message-Id: <20190515090700.812315936@linuxfoundation.org>
In-Reply-To: <20190515090652.640988966@linuxfoundation.org>
References: <20190515090652.640988966@linuxfoundation.org>
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From: Harini Katakam <harini.katakam@xilinx.com>

[ 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@xilinx.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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)
 		napi_enable(&queue->napi);
 
+	bp->macbgem_ops.mog_init_rings(bp);
+	macb_init_hw(bp);
+
 	/* schedule a link state check */
 	phy_start(dev->phydev);