e1000e: test for unusable MSI support

Some systems do not like 82571/2 use of 16-bit MSI messages and some
other systems claim to support MSI, but neither really works.  Setup a
test MSI handler to detect whether or not MSI is working properly, and
if not, fallback to legacy INTx interrupts.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

3 files changed, 164 insertions, 11 deletions

diff --git a/drivers/net/e1000e/defines.h b/drivers/net/e1000e/defines.h
index f823b8ba5785..14b0e6cd3b8d 100644
--- a/drivers/net/e1000e/defines.h
+++ b/drivers/net/e1000e/defines.h
@@ -389,7 +389,7 @@
 
 /* Interrupt Cause Set */
 #define E1000_ICS_LSC       E1000_ICR_LSC       /* Link Status Change */
-#define E1000_ICS_RXDMT0    E1000_ICR_RXDMT0    /* rx desc min. threshold */
+#define E1000_ICS_RXSEQ     E1000_ICR_RXSEQ     /* Rx sequence error */
 #define E1000_ICS_RXDMT0    E1000_ICR_RXDMT0    /* Rx desc min. threshold */
 
 /* Transmit Descriptor Control */
diff --git a/drivers/net/e1000e/e1000.h b/drivers/net/e1000e/e1000.h
index cf57050d99d8..ac4e506b4f88 100644
--- a/drivers/net/e1000e/e1000.h
+++ b/drivers/net/e1000e/e1000.h
@@ -326,6 +326,7 @@ struct e1000_info {
 #define FLAG_RX_CSUM_ENABLED              (1 << 28)
 #define FLAG_TSO_FORCE                    (1 << 29)
 #define FLAG_RX_RESTART_NOW               (1 << 30)
+#define FLAG_MSI_TEST_FAILED              (1 << 31)
 
 #define E1000_RX_DESC_PS(R, i)      \
         (&(((union e1000_rx_desc_packet_split *)((R).desc))[i]))
diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c
index b8b26cf78de5..d266510c8a94 100644
--- a/drivers/net/e1000e/netdev.c
+++ b/drivers/net/e1000e/netdev.c
@@ -1236,26 +1236,36 @@ static irqreturn_t e1000_intr(int irq, void *data)
         return IRQ_HANDLED;
 }
 
+/**
+ * e1000_request_irq - initialize interrupts
+ *
+ * Attempts to configure interrupts using the best available
+ * capabilities of the hardware and kernel.
+ **/
 static int e1000_request_irq(struct e1000_adapter *adapter)
 {
         struct net_device *netdev = adapter->netdev;
-        irq_handler_t handler = e1000_intr;
         int irq_flags = IRQF_SHARED;
         int err;
 
-        if (!pci_enable_msi(adapter->pdev)) {
-                adapter->flags |= FLAG_MSI_ENABLED;
-                handler = e1000_intr_msi;
-                irq_flags = 0;
+        if (!(adapter->flags & FLAG_MSI_TEST_FAILED)) {
+                err = pci_enable_msi(adapter->pdev);
+                if (!err) {
+                        adapter->flags |= FLAG_MSI_ENABLED;
+                        irq_flags = 0;
+                }
         }
 
-        err = request_irq(adapter->pdev->irq, handler, irq_flags, netdev->name,
-                          netdev);
+        err = request_irq(adapter->pdev->irq,
+                          ((adapter->flags & FLAG_MSI_ENABLED) ?
+                                &e1000_intr_msi : &e1000_intr),
+                          irq_flags, netdev->name, netdev);
         if (err) {
-                e_err("Unable to allocate %s interrupt (return: %d)\n",
-                      adapter->flags & FLAG_MSI_ENABLED ? "MSI":"INTx", err);
-                if (adapter->flags & FLAG_MSI_ENABLED)
+                if (adapter->flags & FLAG_MSI_ENABLED) {
                         pci_disable_msi(adapter->pdev);
+                        adapter->flags &= ~FLAG_MSI_ENABLED;
+                }
+                e_err("Unable to allocate interrupt, Error: %d\n", err);
         }
 
         return err;
@@ -2595,6 +2605,135 @@ err:
 }
 
 /**
+ * e1000_intr_msi_test - Interrupt Handler
+ * @irq: interrupt number
+ * @data: pointer to a network interface device structure
+ **/
+static irqreturn_t e1000_intr_msi_test(int 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);
+
+        e_dbg("%s: icr is %08X\n", netdev->name, icr);
+        if (icr & E1000_ICR_RXSEQ) {
+                adapter->flags &= ~FLAG_MSI_TEST_FAILED;
+                wmb();
+        }
+
+        return IRQ_HANDLED;
+}
+
+/**
+ * e1000_test_msi_interrupt - Returns 0 for successful test
+ * @adapter: board private struct
+ *
+ * code flow taken from tg3.c
+ **/
+static int e1000_test_msi_interrupt(struct e1000_adapter *adapter)
+{
+        struct net_device *netdev = adapter->netdev;
+        struct e1000_hw *hw = &adapter->hw;
+        int err;
+
+        /* poll_enable hasn't been called yet, so don't need disable */
+        /* clear any pending events */
+        er32(ICR);
+
+        /* free the real vector and request a test handler */
+        e1000_free_irq(adapter);
+
+        /* Assume that the test fails, if it succeeds then the test
+         * MSI irq handler will unset this flag */
+        adapter->flags |= FLAG_MSI_TEST_FAILED;
+
+        err = pci_enable_msi(adapter->pdev);
+        if (err)
+                goto msi_test_failed;
+
+        err = request_irq(adapter->pdev->irq, &e1000_intr_msi_test, 0,
+                          netdev->name, netdev);
+        if (err) {
+                pci_disable_msi(adapter->pdev);
+                goto msi_test_failed;
+        }
+
+        wmb();
+
+        e1000_irq_enable(adapter);
+
+        /* fire an unusual interrupt on the test handler */
+        ew32(ICS, E1000_ICS_RXSEQ);
+        e1e_flush();
+        msleep(50);
+
+        e1000_irq_disable(adapter);
+
+        rmb();
+
+        if (adapter->flags & FLAG_MSI_TEST_FAILED) {
+                err = -EIO;
+                e_info("MSI interrupt test failed!\n");
+        }
+
+        free_irq(adapter->pdev->irq, netdev);
+        pci_disable_msi(adapter->pdev);
+
+        if (err == -EIO)
+                goto msi_test_failed;
+
+        /* okay so the test worked, restore settings */
+        e_dbg("%s: MSI interrupt test succeeded!\n", netdev->name);
+msi_test_failed:
+        /* restore the original vector, even if it failed */
+        e1000_request_irq(adapter);
+        return err;
+}
+
+/**
+ * e1000_test_msi - Returns 0 if MSI test succeeds or INTx mode is restored
+ * @adapter: board private struct
+ *
+ * code flow taken from tg3.c, called with e1000 interrupts disabled.
+ **/
+static int e1000_test_msi(struct e1000_adapter *adapter)
+{
+        int err;
+        u16 pci_cmd;
+
+        if (!(adapter->flags & FLAG_MSI_ENABLED))
+                return 0;
+
+        /* disable SERR in case the MSI write causes a master abort */
+        pci_read_config_word(adapter->pdev, PCI_COMMAND, &pci_cmd);
+        pci_write_config_word(adapter->pdev, PCI_COMMAND,
+                              pci_cmd & ~PCI_COMMAND_SERR);
+
+        err = e1000_test_msi_interrupt(adapter);
+
+        /* restore previous setting of command word */
+        pci_write_config_word(adapter->pdev, PCI_COMMAND, pci_cmd);
+
+        /* success ! */
+        if (!err)
+                return 0;
+
+        /* EIO means MSI test failed */
+        if (err != -EIO)
+                return err;
+
+        /* back to INTx mode */
+        e_warn("MSI interrupt test failed, using legacy interrupt.\n");
+
+        e1000_free_irq(adapter);
+
+        err = e1000_request_irq(adapter);
+
+        return err;
+}
+
+/**
  * e1000_open - Called when a network interface is made active
  * @netdev: network interface device structure
  *
@@ -2652,6 +2791,19 @@ static int e1000_open(struct net_device *netdev)
         if (err)
                 goto err_req_irq;
 
+        /*
+         * Work around PCIe errata with MSI interrupts causing some chipsets to
+         * ignore e1000e MSI messages, which means we need to test our MSI
+         * interrupt now
+         */
+        {
+                err = e1000_test_msi(adapter);
+                if (err) {
+                        e_err("Interrupt allocation failed\n");
+                        goto err_req_irq;
+                }
+        }
+
         /* From here on the code is the same as e1000e_up() */
         clear_bit(__E1000_DOWN, &adapter->state);