linux-kernel - Re: via-rhine: Problem with lost link after a while

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Message-ID: <20120410225534.GA28480@electric-eye.fr.zoreil.com>
Date:	Wed, 11 Apr 2012 00:55:34 +0200
From:	Francois Romieu <romieu@...zoreil.com>
To:	Bjarke Istrup Pedersen <gurligebis@...too.org>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Svenning Sørensen <sss@...omea.com>,
	Andreas Mohr <andi@...as.de>
Subject: Re: via-rhine: Problem with lost link after a while

Bjarke Istrup Pedersen <gurligebis@...too.org> :
> 10. apr. 2012 22.42 skrev Francois Romieu <romieu@...zoreil.com>:
[...]
> > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;h=3f8c91a7398b9266fbe7abcbe4bd5dffef907643
[...]
> Great, I'll try a 3.4-rc2 kernel, and see how it runs.
> 
> The thread I was talking about earlier is here:
> http://lists.soekris.com/pipermail/soekris-tech/2012-April/018318.html
> Is there any of the changes he has there, that makes sense in the new
> driver you wrote ?

(I did not write a new driver)

Regarding Svenning's patch:
- the wmb in alloc_rbufs may help rhine_reset_task().
- one should probably add one in rhine_rx() as well.
- rhine_start_tx() is supposed to stop queueing when there is no room left.
  I'm curious to know if the "Tx descriptor busy" test triggered.
- the rmb() in rhine_tx() will not make a difference for a single core but
  it's a good reminder that I should not have forgotten to propagate the
  xmit / Tx completion fix back from the r8169 driver to the via-rhine one
  (sigh)

mmiowb is probably missing. I doubt it hits hard right now.

I have not checked if MMIO flushes are missing. Actually I need some sleep.

diff --git a/drivers/net/ethernet/via/via-rhine.c b/drivers/net/ethernet/via/via-rhine.c
index fcfa01f..dfa9fc0 100644
--- a/drivers/net/ethernet/via/via-rhine.c
+++ b/drivers/net/ethernet/via/via-rhine.c
@@ -1163,6 +1163,7 @@ static void alloc_rbufs(struct net_device *dev)
 				       PCI_DMA_FROMDEVICE);
 
 		rp->rx_ring[i].addr = cpu_to_le32(rp->rx_skbuff_dma[i]);
+		wmb();
 		rp->rx_ring[i].rx_status = cpu_to_le32(DescOwn);
 	}
 	rp->dirty_rx = (unsigned int)(i - RX_RING_SIZE);
@@ -1709,8 +1710,13 @@ static netdev_tx_t rhine_start_tx(struct sk_buff *skb,
 	       ioaddr + ChipCmd1);
 	IOSYNC;
 
-	if (rp->cur_tx == rp->dirty_tx + TX_QUEUE_LEN)
+	if (rp->cur_tx == rp->dirty_tx + TX_QUEUE_LEN) {
+		smp_wmb();
 		netif_stop_queue(dev);
+		smp_mb();
+		if (rp->cur_tx != rp->dirty_tx + TX_QUEUE_LEN)
+			netif_wake_queue(dev);
+	}
 
 	netif_dbg(rp, tx_queued, dev, "Transmit frame #%d queued in slot %d\n",
 		  rp->cur_tx - 1, entry);
@@ -1759,6 +1765,7 @@ static void rhine_tx(struct net_device *dev)
 	struct rhine_private *rp = netdev_priv(dev);
 	int txstatus = 0, entry = rp->dirty_tx % TX_RING_SIZE;
 
+	smp_rmb();
 	/* find and cleanup dirty tx descriptors */
 	while (rp->dirty_tx != rp->cur_tx) {
 		txstatus = le32_to_cpu(rp->tx_ring[entry].tx_status);
@@ -1806,8 +1813,12 @@ static void rhine_tx(struct net_device *dev)
 		rp->tx_skbuff[entry] = NULL;
 		entry = (++rp->dirty_tx) % TX_RING_SIZE;
 	}
-	if ((rp->cur_tx - rp->dirty_tx) < TX_QUEUE_LEN - 4)
+
+	smp_mb();
+	if (netif_queue_stopped(dev) &&
+	    (rp->cur_tx - rp->dirty_tx) < TX_QUEUE_LEN - 4) {
 		netif_wake_queue(dev);
+	}
 }
 
 /**
@@ -1947,6 +1958,7 @@ static int rhine_rx(struct net_device *dev, int limit)
 					       PCI_DMA_FROMDEVICE);
 			rp->rx_ring[entry].addr = cpu_to_le32(rp->rx_skbuff_dma[entry]);
 		}
+		wmb();
 		rp->rx_ring[entry].rx_status = cpu_to_le32(DescOwn);
 	}
 
-- 
Ueimor

Will code drivers for food.
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