PCI: portdrv: Restore PCI config state on slot reset

mainline inclusion
from mainline-v4.20-rc1
commit 874b3251
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I47H3V
CVE: NA

--------------------------------

The port's config space may be cleared after a link reset, which wipes out
the bridge's bus and memory windows.  Restore the config space that was
saved during probe so we can access downstream devices.
Signed-off-by: NKeith Busch <keith.busch@intel.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NSinan Kaya <okaya@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/pci/pcie/portdrv_pci.c

@@ -146,6 +146,13 @@ static pci_ers_result_t pcie_portdrv_error_detected(struct pci_dev *dev,
 	return PCI_ERS_RESULT_CAN_RECOVER;
 }
 
+static pci_ers_result_t pcie_portdrv_slot_reset(struct pci_dev *dev)
+{
+	pci_restore_state(dev);
+	pci_save_state(dev);
+	return PCI_ERS_RESULT_RECOVERED;
+}
+
 static pci_ers_result_t pcie_portdrv_mmio_enabled(struct pci_dev *dev)
 {
 	return PCI_ERS_RESULT_RECOVERED;
@@ -185,6 +192,7 @@ static const struct pci_device_id port_pci_ids[] = { {
 
 static const struct pci_error_handlers pcie_portdrv_err_handler = {
 	.error_detected = pcie_portdrv_error_detected,
+	.slot_reset = pcie_portdrv_slot_reset,
 	.mmio_enabled = pcie_portdrv_mmio_enabled,
 	.resume = pcie_portdrv_err_resume,
 };