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From: Nicolas Ferre <nicolas.ferre@atmel.com>
To: <netdev@vger.kernel.org>
Cc: <linux-arm-kernel@lists.infradead.org>, <davem@davemloft.net>,
	<havard@skinnemoen.net>, <nicolas.ferre@atmel.com>,
	<plagnioj@jcrosoft.com>, <jamie@jamieiles.com>,
	<linux-kernel@vger.kernel.org>, <patrice.vilchez@atmel.com>
Subject: [PATCH 04/10] net/macb: Fix a race in macb_start_xmit()
Date: Wed, 5 Sep 2012 10:19:11 +0200	[thread overview]
Message-ID: <40f02ee50a29aaec6c949432a1bcf09f4b027181.1346775479.git.nicolas.ferre@atmel.com> (raw)
In-Reply-To: <cover.1346775479.git.nicolas.ferre@atmel.com>

From: Havard Skinnemoen <havard@skinnemoen.net>

Fix a race in macb_start_xmit() where we unconditionally set the TSTART bit.
If an underrun just happened (we do this with interrupts disabled, so it might
not have been handled yet), the controller starts transmitting from the first
entry in the ring, which is usually wrong.
Restart the controller after error handling.

Signed-off-by: Havard Skinnemoen <havard@skinnemoen.net>
[nicolas.ferre@atmel.com: split patch in topics]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
---
 drivers/net/ethernet/cadence/macb.c |   20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index 2228dfc..f4b8adf 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -390,6 +390,13 @@ static void macb_tx(struct macb *bp)
 		dev_kfree_skb_irq(skb);
 	}
 
+	/*
+	 * Someone may have submitted a new frame while this interrupt
+	 * was pending, or we may just have handled an error.
+	 */
+	if (head != tail && !(status & MACB_BIT(TGO)))
+		macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
+
 	bp->tx_tail = tail;
 	if (netif_queue_stopped(bp->dev) &&
 	    TX_BUFFS_AVAIL(bp) > MACB_TX_WAKEUP_THRESH)
@@ -696,7 +703,18 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	skb_tx_timestamp(skb);
 
-	macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
+	/*
+	 * Only start the controller if the queue was empty; otherwise
+	 * we may race against the hardware resetting the ring pointer
+	 * due to a transmit error.
+	 *
+	 * If the controller is idle but the queue isn't empty, there
+	 * must be a pending interrupt that will trigger as soon as we
+	 * re-enable interrupts, and the interrupt handler will make
+	 * sure the controler is started.
+	 */
+	if (NEXT_TX(bp->tx_tail) == bp->tx_head)
+		macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
 
 	if (TX_BUFFS_AVAIL(bp) < 1)
 		netif_stop_queue(dev);
-- 
1.7.10


  parent reply	other threads:[~2012-09-05  8:19 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-05  8:19 [PATCH 00/10] net/macb: driver enhancement concerning GEM support, ring logic and cleanup Nicolas Ferre
2012-09-05  8:19 ` [PATCH 01/10] net/macb: Add support for Gigabit Ethernet mode Nicolas Ferre
2012-09-05  8:19 ` [PATCH 02/10] net/macb: memory barriers cleanup Nicolas Ferre
2012-09-05  8:19 ` [PATCH 03/10] net/macb: change debugging messages Nicolas Ferre
2012-09-05  8:19 ` Nicolas Ferre [this message]
2012-09-05 21:30   ` [PATCH 04/10] net/macb: Fix a race in macb_start_xmit() David Miller
2012-09-06 14:52     ` Nicolas Ferre
2012-09-06 15:49     ` Havard Skinnemoen
2012-09-07 16:34       ` Nicolas Ferre
2012-09-05  9:00 ` [PATCH 05/10] net/macb: clean up ring buffer logic Nicolas Ferre
2012-09-05  9:00 ` [PATCH 06/10] net/macb: better manage tx errors Nicolas Ferre
2012-09-05  9:00 ` [PATCH 07/10] net/macb: tx status is more than 8 bits now Nicolas Ferre
2012-09-05  9:00 ` [PATCH 08/10] net/macb: macb_get_drvinfo: add GEM/MACB suffix to differentiate revision Nicolas Ferre
2012-09-05 21:31   ` David Miller
2012-09-05 23:27   ` Ben Hutchings
2012-09-06 14:01     ` Nicolas Ferre
2012-09-06 17:42       ` David Miller
2012-09-05  9:00 ` [PATCH 09/10] net/macb: ethtool interface: add register dump feature Nicolas Ferre
2012-09-05 21:32   ` David Miller
2012-09-05 23:36   ` Ben Hutchings
2012-09-06 14:20     ` [PATCH v2 " Nicolas Ferre
2012-09-06 14:34       ` Ben Hutchings
2012-09-05  9:04 ` [PATCH 10/10] net/macb: Offset first RX buffer by two bytes Nicolas Ferre

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