linux-kernel - [PATCH 4.9 33/63] drivers/pci/hotplug: Fix initial state for empty slot

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Date:   Mon, 13 Mar 2017 16:39:20 +0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hank Chang <hankmax0000@...il.com>,
        Gavin Shan <gwshan@...ux.vnet.ibm.com>,
        Willie Liauw <williel@...ermicro.com.tw>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.9 33/63] drivers/pci/hotplug: Fix initial state for empty slot

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gavin Shan <gwshan@...ux.vnet.ibm.com>

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.

Fixes: 360aebd85a4 ("drivers/pci/hotplug: Support surprise hotplug in powernv driver")
Reported-by: Hank Chang <hankmax0000@...il.com>
Signed-off-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>
Tested-by: Willie Liauw <williel@...ermicro.com.tw>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c
@@ -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