[PATCH] pciehp: handle sticky power-fault status

This patch disables power fault, MRL sensor and presence detection
interrupts when a PCIe slot is powered-off and enables those
interrupts when it is powered-on again. This is necessary to prevent
the associated events from causing an endless cycle of interrupts
due to the power-fault bit, which stays set till power is restored
to the slot.

Signed-off-by: Thomas Schaefer <thomas.schaefer@kontron.com>
Signed-off-by: Rajesh Shah <rajesh.shah@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/pci/hotplug/pciehp_hpc.c

@@ -787,8 +787,13 @@ static int hpc_power_on_slot(struct slot * slot)
 
 	slot_cmd = (slot_ctrl & ~PWR_CTRL) | POWER_ON;
 
+	/* Enable detection that we turned off at slot power-off time */
 	if (!pciehp_poll_mode)
-		slot_cmd = slot_cmd | HP_INTR_ENABLE; 
+		slot_cmd = slot_cmd |
+		           PWR_FAULT_DETECT_ENABLE |
+		           MRL_DETECT_ENABLE |
+		           PRSN_DETECT_ENABLE |
+		           HP_INTR_ENABLE;
 
 	retval = pcie_write_cmd(slot, slot_cmd);
 
@@ -833,8 +838,18 @@ static int hpc_power_off_slot(struct slot * slot)
 
 	slot_cmd = (slot_ctrl & ~PWR_CTRL) | POWER_OFF;
 
+	/*
+	 * If we get MRL or presence detect interrupts now, the isr
+	 * will notice the sticky power-fault bit too and issue power
+	 * indicator change commands. This will lead to an endless loop
+	 * of command completions, since the power-fault bit remains on
+	 * till the slot is powered on again.
+	 */
 	if (!pciehp_poll_mode)
-		slot_cmd = slot_cmd | HP_INTR_ENABLE; 
+		slot_cmd = (slot_cmd &
+		            ~PWR_FAULT_DETECT_ENABLE &
+		            ~MRL_DETECT_ENABLE &
+		            ~PRSN_DETECT_ENABLE) | HP_INTR_ENABLE;
 
 	retval = pcie_write_cmd(slot, slot_cmd);