Kexec reboot does not reset PCI devices. If iwlwifi is left running,
the next kernel can time out during probe, breaking networking after
kexec:
kernel: iwlwifi 0000:06:00.0: Host monitor block 0x22 vector 0x0
kernel: iwlwifi 0000:06:00.0: value [iter 0]: 0x00000000
kernel: iwlwifi 0000:06:00.0: probe with driver iwlwifi failed with error -110

Register a dedicated PCI shutdown callback:
run the normal teardown path and then disable the PCI function and
transition it to D3hot so the next kernel can re-initialize it reliably.

Signed-off-by: Li Chen <me@linux.beauty>
---
Changes in v2:
- Don't reuse the ->remove callback for shutdown.
- Disable the PCI function and set D3hot after teardown.

 drivers/net/wireless/intel/iwlwifi/pcie/drv.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
index dc99e7ac4726..e950aab5a39d 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
@@ -1192,6 +1192,21 @@ static void iwl_pci_remove(struct pci_dev *pdev)
 	iwl_pcie_gen1_2_remove(trans);
 }
 
+static void iwl_pci_shutdown(struct pci_dev *pdev)
+{
+	struct iwl_trans *trans = pci_get_drvdata(pdev);
+
+	if (trans) {
+		iwl_pcie_gen1_2_remove(trans);
+		pci_set_drvdata(pdev, NULL);
+	}
+
+	pci_save_state(pdev);
+	pci_clear_master(pdev);
+	pci_disable_device(pdev);
+	pci_set_power_state(pdev, PCI_D3hot);
+}
+
 #ifdef CONFIG_PM_SLEEP
 
 static int iwl_pci_suspend(struct device *device)
@@ -1325,6 +1340,7 @@ static struct pci_driver iwl_pci_driver = {
 	.id_table = iwl_hw_card_ids,
 	.probe = iwl_pci_probe,
 	.remove = iwl_pci_remove,
+	.shutdown = iwl_pci_shutdown,
 	.driver.pm = IWL_PM_OPS,
 	.driver.coredump = iwl_pci_dump,
 };
-- 
2.52.0