gianfar: Fix boot hangs while bringing up gianfar ethernet

Ira Snyder found that commit 8c7396aebb68994c0519e438eecdf4d5fa9c7844
"gianfar: Merge Tx and Rx interrupt for scheduling clean up ring" can
cause hangs. It's because there was removed clearing of interrupts in
gfar_schedule_cleanup() (which is called by an interrupt handler) in
case when netif scheduling has been disabled. This patch brings back
this action and a comment.

Reported-by: Ira Snyder <iws@ovro.caltech.edu>
Reported-by: Peter Korsgaard <jacmet@sunsite.dk>
Bisected-by: Ira Snyder <iws@ovro.caltech.edu>
Tested-by: Peter Korsgaard <jacmet@sunsite.dk>
Tested-by: Ira Snyder <iws@ovro.caltech.edu>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index acae2d8cd688..9b12a13a640f 100644
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -1629,6 +1629,12 @@ static void gfar_schedule_cleanup(struct net_device *dev)
         if (netif_rx_schedule_prep(&priv->napi)) {
                 gfar_write(&priv->regs->imask, IMASK_RTX_DISABLED);
                 __netif_rx_schedule(&priv->napi);
+        } else {
+                /*
+                 * Clear IEVENT, so interrupts aren't called again
+                 * because of the packets that have already arrived.
+                 */
+                gfar_write(&priv->regs->ievent, IEVENT_RTX_MASK);
         }
 
         spin_unlock(&priv->rxlock);