[ 113/187] igbvf: fix divide by zero

Greg Kroah-Hartman
2012-07-12T23:27:29Z

From: Mitch A Williams <mitch.a.williams@intel.com>

commit 0e90b49ca4b891f085b57559a3071a4feefb496c upstream.

Using ethtool -C ethX rx-usecs 0 crashes with a divide by zero.
Refactor this function to fix this issue and make it more clear
what the intent of each conditional is. Add comment regarding
using a setting of zero.

CC: David Ahern <daahern@cisco.com>
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/ethernet/intel/igbvf/ethtool.c | 29 ++++++++++++++++++-----------
1 file changed, 18 insertions(+), 11 deletions(-)

--- a/drivers/net/ethernet/intel/igbvf/ethtool.c
+++ b/drivers/net/ethernet/intel/igbvf/ethtool.c
@@ -357,21 +357,28 @@ static int igbvf_set_coalesce(struct net
struct igbvf_adapter *adapter = netdev_priv(netdev);
struct e1000_hw *hw = &adapter->hw;

- if ((ec->rx_coalesce_usecs > IGBVF_MAX_ITR_USECS) ||
- ((ec->rx_coalesce_usecs > 3) &&
- (ec->rx_coalesce_usecs < IGBVF_MIN_ITR_USECS)) ||
- (ec->rx_coalesce_usecs == 2))
- return -EINVAL;
-
- /* convert to rate of irq's per second */
- if (ec->rx_coalesce_usecs && ec->rx_coalesce_usecs <= 3) {
+ if ((ec->rx_coalesce_usecs >= IGBVF_MIN_ITR_USECS) &&
+ (ec->rx_coalesce_usecs <= IGBVF_MAX_ITR_USECS)) {
+ adapter->current_itr = ec->rx_coalesce_usecs << 2;
+ adapter->requested_itr = 1000000000 /
+ (adapter->current_itr * 256);
+ } else if ((ec->rx_coalesce_usecs == 3) ||
+ (ec->rx_coalesce_usecs == 2)) {
adapter->current_itr = IGBVF_START_ITR;
adapter->requested_itr = ec->rx_coalesce_usecs;
- } else {
- adapter->current_itr = ec->rx_coalesce_usecs << 2;
+ } else if (ec->rx_coalesce_usecs == 0) {
+ /*
+ * The user's desire is to turn off interrupt throttling
+ * altogether, but due to HW limitations, we can't do that.
+ * Instead we set a very small value in EITR, which would
+ * allow ~967k interrupts per second, but allow the adapter's
+ * internal clocking to still function properly.
+ */
+ adapter->current_itr = 4;
adapter->requested_itr = 1000000000 /
(adapter->current_itr * 256);
- }
+ } else
+ return -EINVAL;

writel(adapter->current_itr,
hw->hw_addr + adapter->rx_ring->itr_register);