e1000: allow ethtool coalesece to adjust interrupts per second

This patch allows on-the-fly adjustment of the interrupts per second generated
by e1000 devices 82545/82546 (hardware support of ITR register is a
requirement)

adjust using this command:
ethtool -C eth0 rx-usecs 10

where 10 is 10 microseconds per interrupt interval, so 10 = 100,000 interrupts
per second, and 125 = 8000 interrupts per second.

changes should be immediate.

1,3 are special values and indicate the automatic tuning mode to the driver,
where 1 is 4000-90000 interrupts per second and 3 is 4000-20000 interrupts
per second and is the driver default.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 53 insertions, 1 deletions

diff --git a/drivers/net/e1000/e1000.h b/drivers/net/e1000/e1000.h
index e9a416f40162..c87f2cbdbae3 100644
--- a/drivers/net/e1000/e1000.h
+++ b/drivers/net/e1000/e1000.h
@@ -111,6 +111,9 @@ do {									\
 #define E1000_MIN_RXD                       80
 #define E1000_MAX_82544_RXD               4096
 
+#define E1000_MIN_ITR_USECS             10 /* 100000 irq/sec */
+#define E1000_MAX_ITR_USECS             10000 /* 100    irq/sec */
+
 /* this is the size past which hardware will drop packets when setting LPE=0 */
 #define MAXIMUM_ETHERNET_VLAN_SIZE 1522
 
diff --git a/drivers/net/e1000/e1000_ethtool.c b/drivers/net/e1000/e1000_ethtool.c
index c854c96f5ab3..27f996a2010f 100644
--- a/drivers/net/e1000/e1000_ethtool.c
+++ b/drivers/net/e1000/e1000_ethtool.c
@@ -1904,6 +1904,53 @@ static int e1000_phys_id(struct net_device *netdev, u32 data)
         return 0;
 }
 
+static int e1000_get_coalesce(struct net_device *netdev,
+                              struct ethtool_coalesce *ec)
+{
+        struct e1000_adapter *adapter = netdev_priv(netdev);
+
+        if (adapter->hw.mac_type < e1000_82545)
+                return -EOPNOTSUPP;
+
+        if (adapter->itr_setting <= 3)
+                ec->rx_coalesce_usecs = adapter->itr_setting;
+        else
+                ec->rx_coalesce_usecs = 1000000 / adapter->itr_setting;
+
+        return 0;
+}
+
+static int e1000_set_coalesce(struct net_device *netdev,
+                              struct ethtool_coalesce *ec)
+{
+        struct e1000_adapter *adapter = netdev_priv(netdev);
+        struct e1000_hw *hw = &adapter->hw;
+
+        if (hw->mac_type < e1000_82545)
+                return -EOPNOTSUPP;
+
+        if ((ec->rx_coalesce_usecs > E1000_MAX_ITR_USECS) ||
+            ((ec->rx_coalesce_usecs > 3) &&
+             (ec->rx_coalesce_usecs < E1000_MIN_ITR_USECS)) ||
+            (ec->rx_coalesce_usecs == 2))
+                return -EINVAL;
+
+        if (ec->rx_coalesce_usecs <= 3) {
+                adapter->itr = 20000;
+                adapter->itr_setting = ec->rx_coalesce_usecs;
+        } else {
+                adapter->itr = (1000000 / ec->rx_coalesce_usecs);
+                adapter->itr_setting = adapter->itr & ~3;
+        }
+
+        if (adapter->itr_setting != 0)
+                ew32(ITR, 1000000000 / (adapter->itr * 256));
+        else
+                ew32(ITR, 0);
+
+        return 0;
+}
+
 static int e1000_nway_reset(struct net_device *netdev)
 {
         struct e1000_adapter *adapter = netdev_priv(netdev);
@@ -1978,7 +2025,9 @@ static const struct ethtool_ops e1000_ethtool_ops = {
         .get_strings            = e1000_get_strings,
         .phys_id                = e1000_phys_id,
         .get_ethtool_stats      = e1000_get_ethtool_stats,
-        .get_sset_count         = e1000_get_sset_count,
+        .get_sset_count         = e1000_get_sset_count,
+        .get_coalesce           = e1000_get_coalesce,
+        .set_coalesce           = e1000_set_coalesce,
 };
 
 void e1000_set_ethtool_ops(struct net_device *netdev)