PCI: pciehp: Disable hotplug interrupt during suspend

When PCIe hotplug port is transitioned into D3hot, the link to the
downstream component will go down. If hotplug interrupt generation is
enabled when that happens, it will trigger immediately, waking up the
system and bringing the link back up.

To prevent this, disable hotplug interrupt generation when system suspend
is entered. This does not prevent wakeup from low power states according
to PCIe 4.0 spec section 6.7.3.4:

  Software enables a hot-plug event to generate a wakeup event by
  enabling software notification of the event as described in Section
  6.7.3.1. Note that in order for software to disable interrupt generation
  while keeping wakeup generation enabled, the Hot-Plug Interrupt Enable
  bit must be cleared.

So as long as we have set the slot event mask accordingly, wakeup should
work even if slot interrupt is disabled. The port should trigger wake and
then send PME to the root port when the PCIe hierarchy is brought back up.

Limit this to systems using native PME mechanism to make sure older Apple
systems depending on commit e3354628c376 ("PCI: pciehp: Support interrupts
sent from D3hot") still continue working.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/pci/hotplug/pciehp.h

@@ -176,6 +176,8 @@ struct controller *pcie_init(struct pcie_device *dev);
 int pcie_init_notification(struct controller *ctrl);
 void pcie_shutdown_notification(struct controller *ctrl);
 void pcie_clear_hotplug_events(struct controller *ctrl);
+void pcie_enable_interrupt(struct controller *ctrl);
+void pcie_disable_interrupt(struct controller *ctrl);
 int pciehp_power_on_slot(struct controller *ctrl);
 void pciehp_power_off_slot(struct controller *ctrl);
 void pciehp_get_power_status(struct controller *ctrl, u8 *status);

drivers/pci/hotplug/pciehp_core.c

@@ -242,8 +242,23 @@ static void pciehp_remove(struct pcie_device *dev)
 }
 
 #ifdef CONFIG_PM
+static bool pme_is_native(struct pcie_device *dev)
+{
+	const struct pci_host_bridge *host;
+
+	host = pci_find_host_bridge(dev->port->bus);
+	return pcie_ports_native || host->native_pme;
+}
+
 static int pciehp_suspend(struct pcie_device *dev)
 {
+	/*
+	 * Disable hotplug interrupt so that it does not trigger
+	 * immediately when the downstream link goes down.
+	 */
+	if (pme_is_native(dev))
+		pcie_disable_interrupt(get_service_data(dev));
+
 	return 0;
 }
 
@@ -266,6 +281,9 @@ static int pciehp_resume(struct pcie_device *dev)
 {
 	struct controller *ctrl = get_service_data(dev);
 
+	if (pme_is_native(dev))
+		pcie_enable_interrupt(ctrl);
+
 	pciehp_check_presence(ctrl);
 
 	return 0;

drivers/pci/hotplug/pciehp_hpc.c

@@ -732,6 +732,16 @@ void pcie_clear_hotplug_events(struct controller *ctrl)
 				   PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC);
 }
 
+void pcie_enable_interrupt(struct controller *ctrl)
+{
+	pcie_write_cmd(ctrl, PCI_EXP_SLTCTL_HPIE, PCI_EXP_SLTCTL_HPIE);
+}
+
+void pcie_disable_interrupt(struct controller *ctrl)
+{
+	pcie_write_cmd(ctrl, 0, PCI_EXP_SLTCTL_HPIE);
+}
+
 /*
  * pciehp has a 1:1 bus:slot relationship so we ultimately want a secondary
  * bus reset of the bridge, but at the same time we want to ensure that it is