PCI: pciehp: Don't re-read Slot Status when queuing hotplug event

Previously we read Slot Status to learn about hotplug events, then cleared
the events, then re-read Slot Status to find out what happened.  But Slot
Status might have changed before the second read.

Capture the Slot Status once before clearing the events.  Also capture the
Link Status if we had a link status change.

[bhelgaas: changelog, split to separate patch]
Tested-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NMayurkumar Patel <mayurkumar.patel@intel.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NMika Westerberg <mika.westerberg@linux.intel.com>

drivers/pci/hotplug/pciehp_hpc.c

@@ -566,6 +566,10 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
 	if (!events)
 		return IRQ_NONE;
 
+	/* Capture link status before clearing interrupts */
+	if (events & PCI_EXP_SLTSTA_DLLSC)
+		link = pciehp_check_link_active(ctrl);
+
 	pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, events);
 	ctrl_dbg(ctrl, "pending interrupts %#06x from Slot Status\n", events);
 
@@ -598,7 +602,7 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
 
 	/* Check Presence Detect Changed */
 	if (events & PCI_EXP_SLTSTA_PDC) {
-		pciehp_get_adapter_status(slot, &present);
+		present = !!(status & PCI_EXP_SLTSTA_PDS);
 		ctrl_info(ctrl, "Card %spresent on Slot(%s)\n",
 			  present ? "" : "not ", slot_name(slot));
 		pciehp_queue_interrupt_event(slot, present ? INT_PRESENCE_ON :
@@ -613,7 +617,6 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
 	}
 
 	if (events & PCI_EXP_SLTSTA_DLLSC) {
-		link = pciehp_check_link_active(ctrl);
 		ctrl_info(ctrl, "slot(%s): Link %s event\n",
 			  slot_name(slot), link ? "Up" : "Down");
 		pciehp_queue_interrupt_event(slot, link ? INT_LINK_UP :