e1000e: Fix default interrupt throttle rate not set in NIC HW

Based on the original patch from  Ying Cai <ycai@google.com>
This change ensures that the itr/itr_setting adjustment logic is used,
even for the default/compiled-in value.

Context:
  When we changed the default InterruptThrottleRate value from default
  (3 = dynamic mode) to 8000 for example, only adapter->itr_setting
  (which controls interrupt coalescing mode) was set to 8000, but
  adapter->itr (which controls the value set in NIC register) was not
  updated accordingly. So from ethtool, it seemed the interrupt
  throttling is enabled at 8000 intr/s, but the NIC actually was
  running in dynamic mode which has lower CPU efficiency especially
  when throughput is not high.

CC: Ying Cai <ycai@google.com>
CC: David Decotigny <david.decotigny@google.com>
Signed-off-by: Jeff Kirsher <jeffrey.kirsher@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>

1 files changed, 53 insertions, 46 deletions

diff --git a/drivers/net/ethernet/intel/e1000e/param.c b/drivers/net/ethernet/intel/e1000e/param.c
index ff796e42c3eb..16adeb9418a8 100644
--- a/drivers/net/ethernet/intel/e1000e/param.c
+++ b/drivers/net/ethernet/intel/e1000e/param.c
@@ -106,7 +106,7 @@ E1000_PARAM(RxAbsIntDelay, "Receive Absolute Interrupt Delay");
 /*
  * Interrupt Throttle Rate (interrupts/sec)
  *
- * Valid Range: 100-100000 (0=off, 1=dynamic, 3=dynamic conservative)
+ * Valid Range: 100-100000 or one of: 0=off, 1=dynamic, 3=dynamic conservative
  */
 E1000_PARAM(InterruptThrottleRate, "Interrupt Throttling Rate");
 #define DEFAULT_ITR 3
@@ -344,53 +344,60 @@ void __devinit e1000e_check_options(struct e1000_adapter *adapter)
 
                 if (num_InterruptThrottleRate > bd) {
                         adapter->itr = InterruptThrottleRate[bd];
-                        switch (adapter->itr) {
-                        case 0:
-                                e_info("%s turned off\n", opt.name);
-                                break;
-                        case 1:
-                                e_info("%s set to dynamic mode\n", opt.name);
-                                adapter->itr_setting = adapter->itr;
-                                adapter->itr = 20000;
-                                break;
-                        case 3:
-                                e_info("%s set to dynamic conservative mode\n",
-                                        opt.name);
-                                adapter->itr_setting = adapter->itr;
-                                adapter->itr = 20000;
-                                break;
-                        case 4:
-                                e_info("%s set to simplified (2000-8000 ints) "
-                                       "mode\n", opt.name);
-                                adapter->itr_setting = 4;
-                                break;
-                        default:
-                                /*
-                                 * Save the setting, because the dynamic bits
-                                 * change itr.
-                                 */
-                                if (e1000_validate_option(&adapter->itr, &opt,
-                                                          adapter) &&
-                                    (adapter->itr == 3)) {
-                                        /*
-                                         * In case of invalid user value,
-                                         * default to conservative mode.
-                                         */
-                                        adapter->itr_setting = adapter->itr;
-                                        adapter->itr = 20000;
-                                } else {
-                                        /*
-                                         * Clear the lower two bits because
-                                         * they are used as control.
-                                         */
-                                        adapter->itr_setting =
-                                                adapter->itr & ~3;
-                                }
-                                break;
-                        }
+
+                        /*
+                         * Make sure a message is printed for non-special
+                         * values.  And in case of an invalid option, display
+                         * warning, use default and got through itr/itr_setting
+                         * adjustment logic below
+                         */
+                        if ((adapter->itr > 4) &&
+                            e1000_validate_option(&adapter->itr, &opt, adapter))
+                                adapter->itr = opt.def;
                 } else {
-                        adapter->itr_setting = opt.def;
+                        /*
+                         * If no option specified, use default value and go
+                         * through the logic below to adjust itr/itr_setting
+                         */
+                        adapter->itr = opt.def;
+
+                        /*
+                         * Make sure a message is printed for non-special
+                         * default values
+                         */
+                        if (adapter->itr > 40)
+                                e_info("%s set to default %d\n", opt.name,
+                                       adapter->itr);
+                }
+
+                adapter->itr_setting = adapter->itr;
+                switch (adapter->itr) {
+                case 0:
+                        e_info("%s turned off\n", opt.name);
+                        break;
+                case 1:
+                        e_info("%s set to dynamic mode\n", opt.name);
+                        adapter->itr = 20000;
+                        break;
+                case 3:
+                        e_info("%s set to dynamic conservative mode\n",
+                               opt.name);
                         adapter->itr = 20000;
+                        break;
+                case 4:
+                        e_info("%s set to simplified (2000-8000 ints) mode\n",
+                               opt.name);
+                        break;
+                default:
+                        /*
+                         * Save the setting, because the dynamic bits
+                         * change itr.
+                         *
+                         * Clear the lower two bits because
+                         * they are used as control.
+                         */
+                        adapter->itr_setting &= ~3;
+                        break;
                 }
         }
         { /* Interrupt Mode */