[PATCH iwl-next v1 2/2] ixgbe: Implement PCI reset handler

[Sergey Temerkhanov <sergey.temerkhanov@intel.com>]

Implement PCI device reset handler to allow the network device to
get re-initialized and function after a PCI-level reset.

This is necessary for the adapter to avoid TX queue timeouts
occurring after the PCI reset is performed via sysfs during
its operation.

The reset codepath may trigger a number of dependencies in the
reset of the driver, so that it is necessary to check if
the netdev is present and running there.

Signed-off-by: Sergey Temerkhanov <sergey.temerkhanov@intel.com>
Reviewed-by: Przemyslaw Korba <przemyslaw.korba@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 90 +++++++++++++++++++
 1 file changed, 90 insertions(+)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 42dac766c907..1865b604ace7 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -12358,6 +12358,94 @@ static pci_ers_result_t ixgbe_io_slot_reset(struct pci_dev *pdev)
 	return result;
 }
 
+/**
+ * ixgbe_pci_reset_prepare - called before the pci bus is reset.
+ * @pdev: Pointer to PCI device
+ *
+ * Quiesce the driver in preparation for a PCI function reset. Called from
+ * pci_dev_save_and_disable() before the core saves config state and writes
+ * PCI_COMMAND_INTX_DISABLE to clear bus mastering and MMIO decode, so MMIO
+ * access to the device is still valid here.
+ */
+static void ixgbe_pci_reset_prepare(struct pci_dev *pdev)
+{
+	struct ixgbe_adapter *adapter = pci_get_drvdata(pdev);
+	struct net_device *netdev;
+
+	if (!adapter)
+		return;
+
+	netdev = adapter->netdev;
+
+	rtnl_lock();
+	netif_device_detach(netdev);
+	if (netif_running(netdev))
+		ixgbe_close_suspend(adapter);
+	rtnl_unlock();
+
+	/* __IXGBE_RESETTING is intentionally not set here: it is spun on
+	 * while holding rtnl by ixgbe_reinit_locked(), ixgbe_dcbnl_devreset()
+	 * and the ethtool reset paths, so holding it across the rtnl drop
+	 * would deadlock those callers against ixgbe_pci_reset_done(), which
+	 * needs to re-acquire rtnl.  During the reset window concurrent
+	 * rtnl-holding paths must treat the netdev as detached, while teardown
+	 * paths also observe __IXGBE_DOWN set by ixgbe_down() via
+	 * ixgbe_close_suspend(), matching the existing ixgbe_io_error_detected()
+	 * flow.
+	 */
+
+	if (test_bit(__IXGBE_SERVICE_INITED, &adapter->state)) {
+		/* The service timer was already stopped by ixgbe_down() via
+		 * ixgbe_close_suspend(); if the netdev was not running, the
+		 * timer is not armed.  Only the currently queued service task
+		 * (if any) still needs to be flushed here.
+		 */
+		cancel_work_sync(&adapter->service_task);
+		clear_bit(__IXGBE_SERVICE_SCHED, &adapter->state);
+	}
+}
+
+/**
+ * ixgbe_pci_reset_done - called after the pci bus has been reset.
+ * @pdev: Pointer to PCI device
+ *
+ * Re-initialize the device after a PCI function reset. The PCI core has
+ * already called pci_restore_state() before invoking this callback, so the
+ * saved Command register (including bus mastering) is back in place.
+ */
+static void ixgbe_pci_reset_done(struct pci_dev *pdev)
+{
+	struct ixgbe_adapter *adapter = pci_get_drvdata(pdev);
+	struct net_device *netdev;
+	bool running;
+	int err = 0;
+
+	if (!adapter)
+		return;
+
+	netdev = adapter->netdev;
+
+	rtnl_lock();
+	adapter->hw.hw_addr = adapter->io_addr;
+	ixgbe_reset(adapter);
+	IXGBE_WRITE_REG(&adapter->hw, IXGBE_WUS, ~0);
+	running = netif_running(netdev);
+	if (running) {
+		err = ixgbe_open(netdev);
+		if (err) {
+			e_dev_err("Cannot re-open netdev after PCI reset: %d. A new reset is needed.\n",
+				  err);
+			dev_close(netdev);
+		}
+	}
+	/* Restore presence so userspace can retry later. If ixgbe_open() failed,
+	 * dev_close() cleared IFF_UP first so netif_device_attach() will not wake
+	 * Tx queues without a successful open.
+	 */
+	netif_device_attach(netdev);
+	rtnl_unlock();
+}
+
 /**
  * ixgbe_io_resume - called when traffic can start flowing again.
  * @pdev: Pointer to PCI device
@@ -12390,6 +12478,8 @@ static const struct pci_error_handlers ixgbe_err_handler = {
 	.error_detected = ixgbe_io_error_detected,
 	.slot_reset = ixgbe_io_slot_reset,
 	.resume = ixgbe_io_resume,
+	.reset_prepare = ixgbe_pci_reset_prepare,
+	.reset_done = ixgbe_pci_reset_done,
 };
 
 static DEFINE_SIMPLE_DEV_PM_OPS(ixgbe_pm_ops, ixgbe_suspend, ixgbe_resume);
-- 
2.53.0