[PATCH v2 2/4] e1000e: Do not read icr in Other interrupt

[Benjamin Poirier <bpoirier@suse.com>]

Using eiac instead of reading icr allows us to avoid interference with
rx and tx interrupts in the Other interrupt handler.

According to the 82574 datasheet section 10.2.4.1, interrupt causes that
trigger the Other interrupt are
1) Link Status Change.
2) Receiver Overrun.
3) MDIO Access Complete.
4) Small Receive Packet Detected.
5) Receive ACK Frame Detected.
6) Manageability Event Detected.

Causes 3, 4, 5 are related to features which are not enabled by the
driver. Always assume that cause 1 is what triggered the Other interrupt
and set get_link_status. Cause 2 and 6 should be rare enough that the
extra cost of needlessly re-reading the link status is negligible.

Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index a228167..602fcc9 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -1905,24 +1905,16 @@ static irqreturn_t e1000_msix_other(int __always_unused irq, void *data)
 	struct net_device *netdev = data;
 	struct e1000_adapter *adapter = netdev_priv(netdev);
 	struct e1000_hw *hw = &adapter->hw;
-	u32 icr = er32(ICR);
 
-	if (icr & adapter->eiac_mask)
-		ew32(ICS, (icr & adapter->eiac_mask));
+	/* Assume that the Other interrupt was triggered by LSC */
+	hw->mac.get_link_status = true;
 
-	if (icr & E1000_ICR_OTHER) {
-		if (!(icr & E1000_ICR_LSC))
-			goto no_link_interrupt;
-		hw->mac.get_link_status = true;
-		/* guard against interrupt when we're going down */
-		if (!test_bit(__E1000_DOWN, &adapter->state))
-			mod_timer(&adapter->watchdog_timer, jiffies + 1);
+	/* guard against interrupt when we're going down */
+	if (!test_bit(__E1000_DOWN, &adapter->state)) {
+		mod_timer(&adapter->watchdog_timer, jiffies + 1);
+		ew32(IMS, E1000_IMS_OTHER);
 	}
 
-no_link_interrupt:
-	if (!test_bit(__E1000_DOWN, &adapter->state))
-		ew32(IMS, E1000_IMS_LSC | E1000_IMS_OTHER);
-
 	return IRQ_HANDLED;
 }
 
@@ -2019,6 +2011,7 @@ static void e1000_configure_msix(struct e1000_adapter *adapter)
 		       hw->hw_addr + E1000_EITR_82574(vector));
 	else
 		writel(1, hw->hw_addr + E1000_EITR_82574(vector));
+	adapter->eiac_mask |= E1000_IMS_OTHER;
 
 	/* Cause Tx interrupts on every write back */
 	ivar |= (1 << 31);
@@ -2247,7 +2240,7 @@ static void e1000_irq_enable(struct e1000_adapter *adapter)
 
 	if (adapter->msix_entries) {
 		ew32(EIAC_82574, adapter->eiac_mask & E1000_EIAC_MASK_82574);
-		ew32(IMS, adapter->eiac_mask | E1000_IMS_OTHER | E1000_IMS_LSC);
+		ew32(IMS, adapter->eiac_mask);
 	} else if ((hw->mac.type == e1000_pch_lpt) ||
 		   (hw->mac.type == e1000_pch_spt)) {
 		ew32(IMS, IMS_ENABLE_MASK | E1000_IMS_ECCER);
-- 
2.6.0