RDMA/nes: Fix interrupt moderation low threshold

Interrupt moderation low threshold value was incorrectly triggering,
indicating that the threshold should be lowered.

The impact was the timer was likely to become 40usecs and get stuck
there.  The biggest side effect was too many interrupts and nonoptimal
performance.

Signed-off-by: John Lacombe <jlacombe@neteffect.com>
Signed-off-by: Glenn Streiff <gstreiff@neteffect.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/nes/nes_hw.c

@@ -156,15 +156,14 @@ static void nes_nic_tune_timer(struct nes_device *nesdev)
 
 	spin_lock_irqsave(&nesadapter->periodic_timer_lock, flags);
 
-	if (shared_timer->cq_count_old < cq_count) {
-		if (cq_count > shared_timer->threshold_low)
-			shared_timer->cq_direction_downward=0;
-	}
-	if (shared_timer->cq_count_old >= cq_count)
+	if (shared_timer->cq_count_old <= cq_count)
+		shared_timer->cq_direction_downward = 0;
+	else
 		shared_timer->cq_direction_downward++;
 	shared_timer->cq_count_old = cq_count;
 	if (shared_timer->cq_direction_downward > NES_NIC_CQ_DOWNWARD_TREND) {
-		if (cq_count <= shared_timer->threshold_low) {
+		if (cq_count <= shared_timer->threshold_low &&
+		    shared_timer->threshold_low > 4) {
 			shared_timer->threshold_low = shared_timer->threshold_low/2;
 			shared_timer->cq_direction_downward=0;
 			nesdev->currcq_count = 0;
@@ -1728,7 +1727,6 @@ int nes_napi_isr(struct nes_device *nesdev)
 			nesdev->int_req &= ~NES_INT_TIMER;
 			nes_write32(nesdev->regs+NES_INTF_INT_MASK, ~(nesdev->intf_int_req));
 			nes_write32(nesdev->regs+NES_INT_MASK, ~nesdev->int_req);
-			nesadapter->tune_timer.timer_in_use_old = 0;
 		}
 		nesdev->deepcq_count = 0;
 		return 1;
@@ -1867,7 +1865,6 @@ void nes_dpc(unsigned long param)
 					nesdev->int_req &= ~NES_INT_TIMER;
 					nes_write32(nesdev->regs + NES_INTF_INT_MASK, ~(nesdev->intf_int_req));
 					nes_write32(nesdev->regs+NES_INT_MASK, ~nesdev->int_req);
-					nesdev->nesadapter->tune_timer.timer_in_use_old = 0;
 				} else {
 					nes_write32(nesdev->regs+NES_INT_MASK, 0x0000ffff|(~nesdev->int_req));
 				}

drivers/infiniband/hw/nes/nes_hw.h

@@ -962,7 +962,7 @@ struct nes_arp_entry {
 #define DEFAULT_JUMBO_NES_QL_LOW    12
 #define DEFAULT_JUMBO_NES_QL_TARGET 40
 #define DEFAULT_JUMBO_NES_QL_HIGH   128
-#define NES_NIC_CQ_DOWNWARD_TREND   8
+#define NES_NIC_CQ_DOWNWARD_TREND   16
 
 struct nes_hw_tune_timer {
     //u16 cq_count;