Patch "drivers/pci/hotplug: Fix initial state for empty slot" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

drivers/pci/hotplug: Fix initial state for empty slot

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drivers-pci-hotplug-fix-initial-state-for-empty-slot.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Gavin Shan <[email protected]>
Date: Wed, 11 Jan 2017 11:50:07 +1100
Subject: drivers/pci/hotplug: Fix initial state for empty slot

From: Gavin Shan <[email protected]>

commit d0c424971f70501ec0a0364117b9934db039c9cc upstream.

In PowerNV PCI hotplug driver, the initial PCI slot's state is set to PNV_PHP_STATE_POPULATED if no PCI devices are connected to the slot. The PCI devices that are hot added to the slot won't be probed and populated because of the check in pnv_php_enable():

        /* Check if the slot has been configured */
        if (php_slot->state != PNV_PHP_STATE_REGISTERED)
                return 0;

This fixes the issue by leaving the slot in PNV_PHP_STATE_REGISTERED state initially if nothing is connected to the slot.

---
 drivers/pci/hotplug/pnv_php.c |   16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

@@ -436,9 +436,21 @@ static int pnv_php_enable(struct pnv_php
 	if (ret)
 		return ret;
 
-	/* Proceed if there have nothing behind the slot */
-	if (presence == OPAL_PCI_SLOT_EMPTY)
+	/*
+	 * Proceed if there have nothing behind the slot. However,
+	 * we should leave the slot in registered state at the
+	 * beginning. Otherwise, the PCI devices inserted afterwards
+	 * won't be probed and populated.
+	 */
+	if (presence == OPAL_PCI_SLOT_EMPTY) {
+		if (!php_slot->power_state_check) {
+			php_slot->power_state_check = true;
+
+			return 0;
+		}
+
 		goto scan;
+	}
 
 	/*
 	 * If the power supply to the slot is off, we can't detect

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/pci-hotplug-pnv-php-remove-warn_on-in-pnv_php_put_slot.patch queue-4.9/pci-hotplug-pnv-php-disable-surprise-hotplug-capability-on-conflicts.patch queue-4.9/drivers-pci-hotplug-handle-presence-detection-change-properly.patch queue-4.9/drivers-pci-hotplug-fix-initial-state-for-empty-slot.patch