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net: arc_emac: prevent reuse of unreclaimed tx descriptors

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This patch changes the logic in tx path to ensure that tx descriptors
are reused for transmission only after they have been reclaimed by
arc_emac_tx_clean().

Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Beniamino Galvani 2014-09-10 22:50:03 +02:00 • committed by David S. Miller
commit 74dd40bca9
1 changed files with 32 additions and 11 deletions
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43
drivers/net/ethernet/arc/emac_main.c
View file

@ -29,6 +29,17 @@
#define DRV_NAME "arc_emac" #define DRV_NAME "arc_emac"
#define DRV_VERSION "1.0" #define DRV_VERSION "1.0"
/**
* arc_emac_tx_avail - Return the number of available slots in the tx ring.
* @priv: Pointer to ARC EMAC private data structure.
*
* returns: the number of slots available for transmission in tx the ring.
*/
static inline int arc_emac_tx_avail(struct arc_emac_priv *priv)
{
return (priv->txbd_dirty + TX_BD_NUM - priv->txbd_curr - 1) % TX_BD_NUM;
}
/** /**
* arc_emac_adjust_link - Adjust the PHY link duplex. * arc_emac_adjust_link - Adjust the PHY link duplex.
* @ndev: Pointer to the net_device structure. * @ndev: Pointer to the net_device structure.
@ -180,10 +191,15 @@ static void arc_emac_tx_clean(struct net_device *ndev)
txbd->info = 0; txbd->info = 0;
*txbd_dirty = (*txbd_dirty + 1) % TX_BD_NUM; *txbd_dirty = (*txbd_dirty + 1) % TX_BD_NUM;
if (netif_queue_stopped(ndev))
netif_wake_queue(ndev);
} }
/* Ensure that txbd_dirty is visible to tx() before checking
* for queue stopped.
*/
smp_mb();
if (netif_queue_stopped(ndev) && arc_emac_tx_avail(priv))
netif_wake_queue(ndev);
} }
/** /**
@ -574,11 +590,9 @@ static int arc_emac_tx(struct sk_buff *skb, struct net_device *ndev)
len = max_t(unsigned int, ETH_ZLEN, skb->len); len = max_t(unsigned int, ETH_ZLEN, skb->len);
/* EMAC still holds this buffer in its possession. if (unlikely(!arc_emac_tx_avail(priv))) {
* CPU must not modify this buffer descriptor
*/
if (unlikely((le32_to_cpu(*info) & OWN_MASK) == FOR_EMAC)) {
netif_stop_queue(ndev); netif_stop_queue(ndev);
netdev_err(ndev, "BUG! Tx Ring full when queue awake!\n");
return NETDEV_TX_BUSY; return NETDEV_TX_BUSY;
} }
@ -607,12 +621,19 @@ static int arc_emac_tx(struct sk_buff *skb, struct net_device *ndev)
/* Increment index to point to the next BD */ /* Increment index to point to the next BD */
*txbd_curr = (*txbd_curr + 1) % TX_BD_NUM; *txbd_curr = (*txbd_curr + 1) % TX_BD_NUM;
/* Get "info" of the next BD */ /* Ensure that tx_clean() sees the new txbd_curr before
info = &priv->txbd[*txbd_curr].info; * checking the queue status. This prevents an unneeded wake
* of the queue in tx_clean().
*/
smp_mb();
/* Check if if Tx BD ring is full - next BD is still owned by EMAC */ if (!arc_emac_tx_avail(priv)) {
if (unlikely((le32_to_cpu(*info) & OWN_MASK) == FOR_EMAC))
netif_stop_queue(ndev); netif_stop_queue(ndev);
/* Refresh tx_dirty */
smp_mb();
if (arc_emac_tx_avail(priv))
netif_start_queue(ndev);
}
arc_reg_set(priv, R_STATUS, TXPL_MASK); arc_reg_set(priv, R_STATUS, TXPL_MASK);