blob: fbb09db3e5dec1ec832b254c461a325e97551503 [file] [log] [blame]
From 3db5bcc49b70e7bdcab9a20d804615fd3447f11d Mon Sep 17 00:00:00 2001
From: Finn Thain <fthain@telegraphics.com.au>
Date: Thu, 23 Jan 2020 09:07:26 +1100
Subject: [PATCH] net/sonic: Avoid needless receive descriptor EOL flag updates
commit eaabfd19b2c787bbe88dc32424b9a43d67293422 upstream.
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: efcce839360f ("[PATCH] macsonic/jazzsonic network drivers update")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/net/ethernet/natsemi/sonic.c b/drivers/net/ethernet/natsemi/sonic.c
index c666bbf15116..2cee702f49b8 100644
--- a/drivers/net/ethernet/natsemi/sonic.c
+++ b/drivers/net/ethernet/natsemi/sonic.c
@@ -436,6 +436,7 @@ static void sonic_rx(struct net_device *dev)
struct sonic_local *lp = netdev_priv(dev);
int status;
int entry = lp->cur_rx;
+ int prev_entry = lp->eol_rx;
while (sonic_rda_get(dev, entry, SONIC_RD_IN_USE) == 0) {
struct sk_buff *used_skb;
@@ -516,13 +517,21 @@ static void sonic_rx(struct net_device *dev)
/*
* 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, lp->eol_rx, SONIC_RD_LINK,
- sonic_rda_get(dev, lp->eol_rx, SONIC_RD_LINK) & ~SONIC_EOL);
- lp->eol_rx = entry;
- lp->cur_rx = entry = (entry + 1) & SONIC_RDS_MASK;
+
+ prev_entry = entry;
+ 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()
--
2.7.4