[IB] mthca: Always re-arm EQs in mthca_tavor_interrupt()

We should always re-arm an event queue's interrupt in
mthca_tavor_interrupt() if the corresponding bit is set in the event
cause register (ECR), even if we didn't find any entries in the EQ.
If we don't, then there's a window where we miss an EQ entry and then
get stuck because we don't get another EQ event.
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mthca/mthca_eq.c

@@ -396,20 +396,21 @@ static irqreturn_t mthca_tavor_interrupt(int irq, void *dev_ptr, struct pt_regs
 		writel(dev->eq_table.clr_mask, dev->eq_table.clr_int);
 
 	ecr = readl(dev->eq_regs.tavor.ecr_base + 4);
-	if (ecr) {
+	if (!ecr)
+		return IRQ_NONE;
+
 	writel(ecr, dev->eq_regs.tavor.ecr_base +
 	       MTHCA_ECR_CLR_BASE - MTHCA_ECR_BASE + 4);
 
 	for (i = 0; i < MTHCA_NUM_EQ; ++i)
-			if (ecr & dev->eq_table.eq[i].eqn_mask &&
-			    mthca_eq_int(dev, &dev->eq_table.eq[i])) {
+		if (ecr & dev->eq_table.eq[i].eqn_mask) {
+			if (mthca_eq_int(dev, &dev->eq_table.eq[i]))
 				tavor_set_eq_ci(dev, &dev->eq_table.eq[i],
 						dev->eq_table.eq[i].cons_index);
 			tavor_eq_req_not(dev, dev->eq_table.eq[i].eqn);
 		}
-	}
 
-	return IRQ_RETVAL(ecr);
+	return IRQ_HANDLED;
 }
 
 static irqreturn_t mthca_tavor_msi_x_interrupt(int irq, void *eq_ptr,