[E1000-devel] [PATCH] e1000e: MSI interrupt test failed, using legacy interrupt

[<pra...@ri...>]

From: Prasanna S. Panchamukhi <ppa...@ri...>

Following logs where seen on Systems with multiple NICs & ports,
while using MSI interrupts as shown below:

Feb 16 15:09:32 (none) user.notice kernel: 0000:00:0d.0: lan0_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:32 (none) user.notice kernel: 0000:40:0d.0: wan0_1: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:32 (none) user.notice kernel: 0000:40:0d.0: lan0_1: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:32 (none) user.warn kernel: 0000:40:0e.0: wan4_0: MSI interrupt
test failed, using legacy interrupt.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 16 15:09:32 (none) user.notice kernel: 0000:00:0e.0: wan1_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:33 (none) user.notice kernel: 0000:00:0e.0: lan1_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:33 (none) user.notice kernel: 0000:00:0f.0: wan2_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:33 (none) user.notice kernel: 0000:00:0f.0: lan2_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:33 (none) user.notice kernel: 0000:40:0a.0: wan3_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:33 (none) user.notice kernel: 0000:40:0a.0: lan3_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:34 (none) user.notice kernel: 0000:40:0e.0: lan4_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:34 (none) user.notice kernel: 0000:40:0f.0: wan5_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX
Feb 16 15:09:34 (none) user.notice kernel: 0000:40:0f.0: lan5_0: NIC Link is Up
1000 Mbps Full Duplex, Flow Control: RX/TX

This patch changes the IRQ tests to use polling loops starting with a
delay of 1 tick and doubling that if necessary up to a maximum total
delay of approximately 1 second.

Signed-off-by: Prasanna S. Panchamukhi <ppa...@ri...>
---
 drivers/net/ethernet/intel/e1000e/netdev.c |   27 +++++++++++++++++++++++----
 1 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 19ab215..8ff0fff 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -98,6 +98,16 @@ struct e1000_reg_info {
 #define E1000_TDFTS	0x03428	/* Tx Data FIFO Tail Saved - RW */
 #define E1000_TDFPC	0x03430	/* Tx Data FIFO Packet Count - RW */
 
+/* IRQ latency can be enormous because:
+ * - All IRQs may be disabled on a CPU for a *long* time by e.g. a
+ *   slow serial console or an old IDE driver doing error recovery
+ * - The PREEMPT_RT patches mostly deal with this, but also allow a
+ *   tasklet or normal task to be given higher priority than our IRQ
+ *   threads
+ * Try to avoid blaming the hardware for this.
+ */
+#define IRQ_TIMEOUT HZ
+
 static const struct e1000_reg_info e1000_reg_info_tbl[] = {
 
 	/* General Registers */
@@ -3767,6 +3777,7 @@ static int e1000_test_msi_interrupt(struct e1000_adapter *adapter)
 {
 	struct net_device *netdev = adapter->netdev;
 	struct e1000_hw *hw = &adapter->hw;
+	unsigned long timeout, wait;
 	int err;
 
 	/* poll_enable hasn't been called yet, so don't need disable */
@@ -3799,12 +3810,20 @@ static int e1000_test_msi_interrupt(struct e1000_adapter *adapter)
 	/* fire an unusual interrupt on the test handler */
 	ew32(ICS, E1000_ICS_RXSEQ);
 	e1e_flush();
-	msleep(50);
-
+	timeout = jiffies + IRQ_TIMEOUT;
+	wait = 1;
+	e_dbg("Waiting for MSI interrupt!\n");
+	do {
+		schedule_timeout_uninterruptible(wait);
+		rmb();
+		if (!(adapter->flags & FLAG_MSI_TEST_FAILED))
+			goto success;
+		wait *= 2;
+	} while (time_before(jiffies, timeout));
+
+success:
 	e1000_irq_disable(adapter);
 
-	rmb();
-
 	if (adapter->flags & FLAG_MSI_TEST_FAILED) {
 		adapter->int_mode = E1000E_INT_MODE_LEGACY;
 		e_info("MSI interrupt test failed, using legacy interrupt.\n");
-- 
1.7.0.4