[PATCHv4 06/12] PCI: ERR: Use slot reset if available

[Keith Busch <keith.busch@xxxxxxxxx>]

The secondary bus reset may have link side effects that a hot plug
capable port may incorrectly react to. This patch will use the slot
specific reset for hotplug ports, fixing the undesirable link down-up
handling during error recovering.

Signed-off-by: Keith Busch <keith.busch@xxxxxxxxx>
---
 drivers/pci/pci.c      | 33 +++++++++++++++++++++++++++++++++
 drivers/pci/pci.h      |  2 ++
 drivers/pci/pcie/aer.c |  2 +-
 drivers/pci/pcie/err.c |  2 +-
 drivers/pci/slot.c     |  2 +-
 5 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index bcb70b7c190c..ce4dafbfe2d1 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5169,6 +5169,39 @@ static int pci_bus_reset(struct pci_bus *bus, int probe)
 	return ret;
 }
 
+/**
+ * pci_bus_error_reset - reset the bridge's subordinate bus
+ * @bridge: The parent device that connects to the bus to reset
+ *
+ * This function will first try to reset the slots on this bus if the method is
+ * available. If slot reset fails or is not available, this will fall back to a
+ * secondary bus reset.
+ */
+int pci_bus_error_reset(struct pci_dev *bridge)
+{
+	struct pci_bus *bus = bridge->subordinate;
+
+	if (!bus)
+		return -ENOTTY;
+
+	mutex_lock(&pci_slot_mutex);
+	if (!list_empty(&bus->slots)) {
+		struct pci_slot *slot;
+
+		list_for_each_entry(slot, &bus->slots, list)
+			if (pci_probe_reset_slot(slot))
+				goto bus_reset;
+		list_for_each_entry(slot, &bus->slots, list)
+			if (pci_slot_reset(slot, 0))
+				goto bus_reset;
+	}
+	mutex_unlock(&pci_slot_mutex);
+	return 0;
+bus_reset:
+	mutex_unlock(&pci_slot_mutex);
+	return pci_bus_reset(bridge->subordinate, 0);
+}
+
 /**
  * pci_probe_reset_bus - probe whether a PCI bus can be reset
  * @bus: PCI bus to probe
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 5a5c6099b253..807e31e24fd0 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -35,6 +35,7 @@ int pci_mmap_fits(struct pci_dev *pdev, int resno, struct vm_area_struct *vmai,
 
 int pci_probe_reset_function(struct pci_dev *dev);
 int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
+int pci_bus_error_reset(struct pci_dev *dev);
 
 /**
  * struct pci_platform_pm_ops - Firmware PM callbacks
@@ -136,6 +137,7 @@ static inline void pci_remove_legacy_files(struct pci_bus *bus) { return; }
 
 /* Lock for read/write access to pci device and bus lists */
 extern struct rw_semaphore pci_bus_sem;
+extern struct mutex pci_slot_mutex;
 
 extern raw_spinlock_t pci_lock;
 
diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index 5c3ea7254c6a..1563e22600ec 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -1528,7 +1528,7 @@ static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
 	reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
 	pci_write_config_dword(dev, pos + PCI_ERR_ROOT_COMMAND, reg32);
 
-	rc = pci_bridge_secondary_bus_reset(dev);
+	rc = pci_bus_error_reset(dev);
 	pci_printk(KERN_DEBUG, dev, "Root Port link has been reset\n");
 
 	/* Clear Root Error Status */
diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index cac406b6e936..62ab665f0f03 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -177,7 +177,7 @@ static pci_ers_result_t default_reset_link(struct pci_dev *dev)
 {
 	int rc;
 
-	rc = pci_bridge_secondary_bus_reset(dev);
+	rc = pci_bus_error_reset(dev);
 	pci_printk(KERN_DEBUG, dev, "downstream link has been reset\n");
 	return rc ? PCI_ERS_RESULT_DISCONNECT : PCI_ERS_RESULT_RECOVERED;
 }
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index 145cd953b518..3da03fcc6fbf 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -14,7 +14,7 @@
 
 struct kset *pci_slots_kset;
 EXPORT_SYMBOL_GPL(pci_slots_kset);
-static DEFINE_MUTEX(pci_slot_mutex);
+DEFINE_MUTEX(pci_slot_mutex);
 
 static ssize_t pci_slot_attr_show(struct kobject *kobj,
 					struct attribute *attr, char *buf)
-- 
2.14.4