Commit eaabfd19 authored by Finn Thain's avatar Finn Thain Committed by David S. Miller

net/sonic: Avoid needless receive descriptor EOL flag updates

The while loop in sonic_rx() traverses the rx descriptor ring. It stops
when it reaches a descriptor that the SONIC has not used. Each iteration
advances the EOL flag so the SONIC can keep using more descriptors.
Therefore, the while loop has no definite termination condition.

The algorithm described in the National Semiconductor literature is quite
different. It consumes descriptors up to the one with its EOL flag set
(which will also have its "in use" flag set). All freed descriptors are
then returned to the ring at once, by adjusting the EOL flags (and link
pointers).

Adopt the algorithm from datasheet as it's simpler, terminates quickly
and avoids a lot of pointless descriptor EOL flag changes.

Fixes: efcce839 ("[PATCH] macsonic/jazzsonic network drivers update")
Tested-by: default avatarStan Johnson <userm57@yahoo.com>
Signed-off-by: default avatarFinn Thain <fthain@telegraphics.com.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9e311820
...@@ -436,6 +436,7 @@ static void sonic_rx(struct net_device *dev) ...@@ -436,6 +436,7 @@ static void sonic_rx(struct net_device *dev)
struct sonic_local *lp = netdev_priv(dev); struct sonic_local *lp = netdev_priv(dev);
int status; int status;
int entry = lp->cur_rx; int entry = lp->cur_rx;
int prev_entry = lp->eol_rx;
while (sonic_rda_get(dev, entry, SONIC_RD_IN_USE) == 0) { while (sonic_rda_get(dev, entry, SONIC_RD_IN_USE) == 0) {
struct sk_buff *used_skb; struct sk_buff *used_skb;
...@@ -516,13 +517,21 @@ static void sonic_rx(struct net_device *dev) ...@@ -516,13 +517,21 @@ static void sonic_rx(struct net_device *dev)
/* /*
* give back the descriptor * give back the descriptor
*/ */
sonic_rda_put(dev, entry, SONIC_RD_LINK,
sonic_rda_get(dev, entry, SONIC_RD_LINK) | SONIC_EOL);
sonic_rda_put(dev, entry, SONIC_RD_IN_USE, 1); sonic_rda_put(dev, entry, SONIC_RD_IN_USE, 1);
sonic_rda_put(dev, lp->eol_rx, SONIC_RD_LINK,
sonic_rda_get(dev, lp->eol_rx, SONIC_RD_LINK) & ~SONIC_EOL); prev_entry = entry;
lp->eol_rx = entry; entry = (entry + 1) & SONIC_RDS_MASK;
lp->cur_rx = entry = (entry + 1) & SONIC_RDS_MASK; }
lp->cur_rx = entry;
if (prev_entry != lp->eol_rx) {
/* Advance the EOL flag to put descriptors back into service */
sonic_rda_put(dev, prev_entry, SONIC_RD_LINK, SONIC_EOL |
sonic_rda_get(dev, prev_entry, SONIC_RD_LINK));
sonic_rda_put(dev, lp->eol_rx, SONIC_RD_LINK, ~SONIC_EOL &
sonic_rda_get(dev, lp->eol_rx, SONIC_RD_LINK));
lp->eol_rx = prev_entry;
} }
/* /*
* If any worth-while packets have been received, netif_rx() * If any worth-while packets have been received, netif_rx()
......
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