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>

diff --git a/drivers/net/ethernet/intel/e1000e/param.c b/drivers/net/ethernet/intel/e1000e/param.c
index ff796e42c3ebbf1b146a28b677e7bb885e1f6bf6..16adeb9418a8903e5ccbb7503e513f1918978930 100644 (file)
--- 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 */