PCI: Add flag for devices where we can't use bus reset

Enable a mechanism for devices to quirk that they do not behave when
doing a PCI bus reset.  We require a modest level of spec compliant
behavior in order to do a reset, for instance the device should come
out of reset without throwing errors and PCI config space should be
accessible after reset.  This is too much to ask for some devices.

Link: http://lkml.kernel.org/r/20140923210318.498dacbd@dualc.maya.org
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v3.14+

1 files changed, 36 insertions, 4 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index cab05f3..e9d4fd8 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3271,7 +3271,8 @@ static int pci_parent_bus_reset(struct pci_dev *dev, int probe)
 {
 	struct pci_dev *pdev;
 
-	if (pci_is_root_bus(dev->bus) || dev->subordinate || !dev->bus->self)
+	if (pci_is_root_bus(dev->bus) || dev->subordinate ||
+	    !dev->bus->self || dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET)
 		return -ENOTTY;
 
 	list_for_each_entry(pdev, &dev->bus->devices, bus_list)
@@ -3305,7 +3306,8 @@ static int pci_dev_reset_slot_function(struct pci_dev *dev, int probe)
 {
 	struct pci_dev *pdev;
 
-	if (dev->subordinate || !dev->slot)
+	if (dev->subordinate || !dev->slot ||
+	    dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET)
 		return -ENOTTY;
 
 	list_for_each_entry(pdev, &dev->bus->devices, bus_list)
@@ -3557,6 +3559,20 @@ int pci_try_reset_function(struct pci_dev *dev)
 }
 EXPORT_SYMBOL_GPL(pci_try_reset_function);
 
+/* Do any devices on or below this bus prevent a bus reset? */
+static bool pci_bus_resetable(struct pci_bus *bus)
+{
+	struct pci_dev *dev;
+
+	list_for_each_entry(dev, &bus->devices, bus_list) {
+		if (dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET ||
+		    (dev->subordinate && !pci_bus_resetable(dev->subordinate)))
+			return false;
+	}
+
+	return true;
+}
+
 /* Lock devices from the top of the tree down */
 static void pci_bus_lock(struct pci_bus *bus)
 {
@@ -3607,6 +3623,22 @@ unlock:
 	return 0;
 }
 
+/* Do any devices on or below this slot prevent a bus reset? */
+static bool pci_slot_resetable(struct pci_slot *slot)
+{
+	struct pci_dev *dev;
+
+	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
+		if (!dev->slot || dev->slot != slot)
+			continue;
+		if (dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET ||
+		    (dev->subordinate && !pci_bus_resetable(dev->subordinate)))
+			return false;
+	}
+
+	return true;
+}
+
 /* Lock devices from the top of the tree down */
 static void pci_slot_lock(struct pci_slot *slot)
 {
@@ -3728,7 +3760,7 @@ static int pci_slot_reset(struct pci_slot *slot, int probe)
 {
 	int rc;
 
-	if (!slot)
+	if (!slot || !pci_slot_resetable(slot))
 		return -ENOTTY;
 
 	if (!probe)
@@ -3820,7 +3852,7 @@ EXPORT_SYMBOL_GPL(pci_try_reset_slot);
 
 static int pci_bus_reset(struct pci_bus *bus, int probe)
 {
-	if (!bus->self)
+	if (!bus->self || !pci_bus_resetable(bus))
 		return -ENOTTY;
 
 	if (probe)