PCI: pciehp: Use link change notifications for hot-plug and removal

A lot of systems do not have the fancy buttons and LEDs, and instead
want to rely only on the Link state change events to drive the hotplug
and removal state machinery.
(http://www.spinics.net/lists/hotplug/msg05802.html)

This patch adds support for that functionality. Here are the details
about the patch itself:

* Define and use interrupt events for linkup / linkdown.

* Make the pcie_isr() also look at link events, and direct control to
  corresponding (new) link state change handler function.

* Introduce the functions to handle link-up and link-down events and
  queue the add / removal work in the slot->wq to be processed by
  pciehp_power_thread()

As a side note, this patch also fixes the bug
https://bugzilla.kernel.org/show_bug.cgi?id=65521 "pciehp ignores Data Link
Layer State Changed bit."

Signed-off-by: Rajat Jain <rajatxjain@gmail.com>
Signed-off-by: Rajat Jain <rajatjain@juniper.net>
Signed-off-by: Guenter Roeck <groeck@juniper.net>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
index f952459..d8d03361 100644
--- a/drivers/pci/hotplug/pciehp.h
+++ b/drivers/pci/hotplug/pciehp.h
@@ -109,6 +109,8 @@
 #define INT_BUTTON_PRESS		7
 #define INT_BUTTON_RELEASE		8
 #define INT_BUTTON_CANCEL		9
+#define INT_LINK_UP			10
+#define INT_LINK_DOWN			11
 
 #define STATIC_STATE			0
 #define BLINKINGON_STATE		1
@@ -132,6 +134,7 @@
 u8 pciehp_handle_switch_change(struct slot *p_slot);
 u8 pciehp_handle_presence_change(struct slot *p_slot);
 u8 pciehp_handle_power_fault(struct slot *p_slot);
+void pciehp_handle_linkstate_change(struct slot *p_slot);
 int pciehp_configure_device(struct slot *p_slot);
 int pciehp_unconfigure_device(struct slot *p_slot);
 void pciehp_queue_pushbutton_work(struct work_struct *work);