PCI: pciehp: Obey compulsory command delay after resume

Upon resume from system sleep, the Slot Control register is written via:

  pci_pm_resume_noirq()
    pci_pm_default_resume_early()
      pci_restore_state()
        pci_restore_pcie_state()

PCIe r4.0, sec 6.7.3.2 says that after "issuing a write transaction that
targets any portion of the Port's Slot Control register, [...] software
must wait for [the] command to complete before issuing the next command".

pciehp currently fails to enforce that rule after the above-mentioned
write.  Fix it.

(Moving restoration of the Slot Control register to pciehp doesn't seem
to make sense because the other PCIe hotplug drivers may need it as
well.)

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/hotplug/pciehp_core.c

@@ -284,6 +284,10 @@ static int pciehp_resume_noirq(struct pcie_device *dev)
 	struct controller *ctrl = get_service_data(dev);
 	struct slot *slot = ctrl->slot;
 
+	/* pci_restore_state() just wrote to the Slot Control register */
+	ctrl->cmd_started = jiffies;
+	ctrl->cmd_busy = true;
+
 	/* clear spurious events from rediscovery of inserted card */
 	if (slot->state == ON_STATE || slot->state == BLINKINGOFF_STATE)
 		pcie_clear_hotplug_events(ctrl);