PCI: pciehp: Prioritize data-link event over presence detect

If Slot Status indicates changes in both Data Link Layer Status and
Presence Detect, prioritize the Link status change.

When both events are observed, pciehp currently relies on the Slot Status
Presence Detect State (PDS) to agree with the Link Status Data Link Layer
Active status.  The Presence Detect State, however, may be set to 1 through
out-of-band presence detect even if the link is down, which creates
conflicting events.

Since the Link Status accurately reflects the reachability of the
downstream bus, the Link Status event should take precedence over a
Presence Detect event.  Skip checking the PDC status if we handled a link
event in the same handler.

Orabug: 25312751

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Altered slightly for UEK4.1
(cherry picked from commit 385895fef6b5f4723e33d0e58251c45bc708132d)
Signed-off-by: Jack Vogel <jack.vogel@oracle.com>
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 0ebf754fc1775d7afffdc6fb9bea37828408d24a..6b52bab9493d2a545c6d08cf22dfada419e0724a 100644 (file)
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -562,8 +562,16 @@ static irqreturn_t pcie_isr(int irq, void *dev_id)
        if (intr_loc & PCI_EXP_SLTSTA_ABP)
                pciehp_handle_attention_button(slot);
 
-       /* Check Presence Detect Changed */
-       if (intr_loc & PCI_EXP_SLTSTA_PDC)
+       /*
+        * Check Link Status Changed at higher precedence than Presence
+        * Detect Changed.  The PDS value may be set to "card present" from
+        * out-of-band detection, which may be in conflict with a Link Down
+        * and cause the wrong event to queue. We can skip the PDC if we
+        * are handling a link event in the same handler.
+        */
+       if (intr_loc & PCI_EXP_SLTSTA_DLLSC)
+               pciehp_handle_linkstate_change(slot);
+       else if (intr_loc & PCI_EXP_SLTSTA_PDC)
                pciehp_handle_presence_change(slot);
 
        /* Check Power Fault Detected */
@@ -572,9 +580,6 @@ static irqreturn_t pcie_isr(int irq, void *dev_id)
                pciehp_handle_power_fault(slot);
        }
 
-       if (intr_loc & PCI_EXP_SLTSTA_DLLSC)
-               pciehp_handle_linkstate_change(slot);
-
        return IRQ_HANDLED;
 }