diff options
| author | Scott Wood <scottwood@freescale.com> | 2007-05-16 15:06:59 -0500 |
|---|---|---|
| committer | Jeff Garzik <jeff@garzik.org> | 2007-05-17 20:43:15 -0400 |
| commit | 3b6330ce2a3e1f152f79a6203f73d23356e243a7 (patch) | |
| tree | 3325c488b05be904ecddd176a1eea3cb3fe2e6a1 | |
| parent | dbf2e8585971f2a8b1f60a188dc245fd2f8f81b3 (diff) | |
| download | linux-3b6330ce2a3e1f152f79a6203f73d23356e243a7.tar.bz2 | |
gianfar: Add I/O barriers when touching buffer descriptor ownership.
The hardware must not see that is given ownership of a buffer until it is
completely written, and when the driver receives ownership of a buffer,
it must ensure that any other reads to the buffer reflect its final
state. Thus, I/O barriers are added where required.
Without this patch, I have observed GCC reordering the setting of
bdp->length and bdp->status in gfar_new_skb. Hardware reordering
was also theoretically possible.
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
| -rw-r--r-- | drivers/net/gianfar.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c index b666a0cc0642..f5b3cba23fc5 100644 --- a/drivers/net/gianfar.c +++ b/drivers/net/gianfar.c @@ -1025,6 +1025,15 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev) dev->trans_start = jiffies; + /* The powerpc-specific eieio() is used, as wmb() has too strong + * semantics (it requires synchronization between cacheable and + * uncacheable mappings, which eieio doesn't provide and which we + * don't need), thus requiring a more expensive sync instruction. At + * some point, the set of architecture-independent barrier functions + * should be expanded to include weaker barriers. + */ + + eieio(); txbdp->status = status; /* If this was the last BD in the ring, the next one */ @@ -1301,6 +1310,7 @@ struct sk_buff * gfar_new_skb(struct net_device *dev, struct rxbd8 *bdp) bdp->length = 0; /* Mark the buffer empty */ + eieio(); bdp->status |= (RXBD_EMPTY | RXBD_INTERRUPT); return skb; @@ -1484,6 +1494,7 @@ int gfar_clean_rx_ring(struct net_device *dev, int rx_work_limit) bdp = priv->cur_rx; while (!((bdp->status & RXBD_EMPTY) || (--rx_work_limit < 0))) { + rmb(); skb = priv->rx_skbuff[priv->skb_currx]; if (!(bdp->status & |