[PATCH net v2] net: libwx: fix PM suspend/resume flow for VF drivers

[Mengyuan Lou <mengyuanlou@net-swift.com>]

In the current wxvf_suspend() and wxvf_resume() implementations, power
management operations lack synchronization with network device
configuration, and proper hardware cleanup/restoration lifecycle
handling is missing.
Specifically:

1. Operations are not guarded by rtnl_lock(), leading to potential race
   conditions with concurrent netdevice callbacks.
2. The suspend path leaves background work and timers running, omits
   disabling TX queues/NAPI instances, and fails to release IRQ and ring
   resources when the interface is up.
3. The resume path does not re-enable the PCI device with MEM access, lacks
   re-allocation and request of MSI-X IRQs/resources, and missing proper
   unroll error handling upon failures.

Fix these issues with the following changes:

- Synchronize both suspend and resume handlers under rtnl_lock().
- In wxvf_suspend(), synchronously cancel background timers/service tasks,
  clear state flags, bring down queues and NAPI, free IRQ/resources if
  running, and clear PCI bus master flag before disabling the device.
- In wxvf_resume(), re-enable the PCI device via pci_enable_device_mem(),
  re-initialize the interrupt scheme, and for running interfaces,
  re-allocate resources, re-request MSI-X IRQs, triggering
  WX_FLAG_NEED_DO_RESET for subsequent HW reset handling, and attach the
  device. Complete error handling paths are added to rollback safely on
  failures.

Fixes: 377d180bd71c ("net: wangxun: add txgbevf build")
Signed-off-by: Mengyuan Lou <mengyuanlou@net-swift.com>
---
Changelogs:
v2:
- Refactored the suspend and resume logic to eliminate full netdevice close/open
  cycles in favor of lightweight interrupt and queue manipulation:
  * In wxvf_suspend(), replaced wxvf_close() with explicit queue stopping
    (netif_tx_disable), carrier drop, NAPI disabling (wx_napi_disable_all), IRQ
    releasing (wx_free_irq), and resource freeing (wx_free_resources).
  * In wxvf_resume(), replaced wxvf_open() with granular resource allocation
    (wx_setup_resources), MSI-X IRQ requesting (wx_request_msix_irqs_vf), and deferred
    hardware reconfiguration via WX_FLAG_NEED_DO_RESET flag.
- Dropped the addition of device_link_add() to parent PF in ngbevf and txgbevf probe()
  paths to keep the patch focused strictly on libwx PM suspend/resume flow.
v1: https://lore.kernel.org/netdev/20260826095243.16939-1-mengyuanlou@net-swift.com/
---
 .../net/ethernet/wangxun/libwx/wx_vf_common.c | 62 ++++++++++++++++++-
 1 file changed, 59 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/wangxun/libwx/wx_vf_common.c b/drivers/net/ethernet/wangxun/libwx/wx_vf_common.c
index 26de78e9a69e..8a212e36c3d8 100644
--- a/drivers/net/ethernet/wangxun/libwx/wx_vf_common.c
+++ b/drivers/net/ethernet/wangxun/libwx/wx_vf_common.c
@@ -15,10 +15,26 @@ int wxvf_suspend(struct device *dev_d)
 {
 	struct pci_dev *pdev = to_pci_dev(dev_d);
 	struct wx *wx = pci_get_drvdata(pdev);
+	struct net_device *netdev;
 
-	netif_device_detach(wx->netdev);
+	netdev = wx->netdev;
+	timer_delete_sync(&wx->service_timer);
+	cancel_work_sync(&wx->service_task);
+	clear_bit(WX_STATE_SERVICE_SCHED, wx->state);
+
+	rtnl_lock();
+	netif_device_detach(netdev);
+	if (netif_running(netdev)) {
+		netif_tx_disable(netdev);
+		netif_carrier_off(netdev);
+		wx_napi_disable_all(wx);
+		wx_free_irq(wx);
+		wx_free_resources(wx);
+	}
 	wx_clear_interrupt_scheme(wx);
+	pci_clear_master(pdev);
 	pci_disable_device(pdev);
+	rtnl_unlock();
 
 	return 0;
 }
@@ -34,12 +50,52 @@ int wxvf_resume(struct device *dev_d)
 {
 	struct pci_dev *pdev = to_pci_dev(dev_d);
 	struct wx *wx = pci_get_drvdata(pdev);
+	struct net_device *netdev;
+	int err;
+
+	netdev = wx->netdev;
+	err = pci_enable_device_mem(pdev);
+	if (err) {
+		dev_err(&pdev->dev, "Cannot enable PCI device from suspend\n");
+		return err;
+	}
 
 	pci_set_master(pdev);
-	wx_init_interrupt_scheme(wx);
-	netif_device_attach(wx->netdev);
+	rtnl_lock();
+
+	err = wx_init_interrupt_scheme(wx);
+	if (err)
+		goto err_pci;
+
+	/* Since vf resume before than pf, only the vf interrupt and software
+	 * resources need to be initialized. The hardware configuration will be
+	 * reconfigured in reset subtask.
+	 */
+	if (netif_running(netdev)) {
+		err = wx_setup_resources(wx);
+		if (err)
+			goto err_clear_int;
+
+		err = wx_request_msix_irqs_vf(wx);
+		if (err)
+			goto err_free_resources;
+
+		wxvf_up_complete(wx);
+		set_bit(WX_FLAG_NEED_DO_RESET, wx->flags);
+	}
+
+	netif_device_attach(netdev);
+	rtnl_unlock();
 
 	return 0;
+err_free_resources:
+	wx_free_resources(wx);
+err_clear_int:
+	wx_clear_interrupt_scheme(wx);
+err_pci:
+	rtnl_unlock();
+	pci_disable_device(pdev);
+	return err;
 }
 EXPORT_SYMBOL(wxvf_resume);
 
-- 
2.30.1