s390/pci: implement reset_slot for hotplug slot

This is done by adding a zpci_hot_reset_device() call which does a low
level reset of the PCI function without changing its higher level
function state. This way it can be used while the zPCI function is bound
to a driver and with DMA tables being controlled either through the
IOMMU or DMA APIs which is prohibited when using zpci_disable_device()
as that drop existing DMA translations.

As this reset, unlike a normal FLR, also calls zpci_clear_irq() we need
to implement arch_restore_msi_irqs() and make sure we re-enable IRQs for
the PCI function if they were previously disabled.

Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/drivers/pci/hotplug/s390_pci_hpc.c b/drivers/pci/hotplug/s390_pci_hpc.c
index dcefdb42ac46..a89b7de72dcf 100644
--- a/drivers/pci/hotplug/s390_pci_hpc.c
+++ b/drivers/pci/hotplug/s390_pci_hpc.c
@@ -57,6 +57,29 @@ static int disable_slot(struct hotplug_slot *hotplug_slot)
 	return zpci_deconfigure_device(zdev);
 }
 
+static int reset_slot(struct hotplug_slot *hotplug_slot, bool probe)
+{
+	struct zpci_dev *zdev = container_of(hotplug_slot, struct zpci_dev,
+					     hotplug_slot);
+
+	if (zdev->state != ZPCI_FN_STATE_CONFIGURED)
+		return -EIO;
+	/*
+	 * We can't take the zdev->lock as reset_slot may be called during
+	 * probing and/or device removal which already happens under the
+	 * zdev->lock. Instead the user should use the higher level
+	 * pci_reset_function() or pci_bus_reset() which hold the PCI device
+	 * lock preventing concurrent removal. If not using these functions
+	 * holding the PCI device lock is required.
+	 */
+
+	/* As long as the function is configured we can reset */
+	if (probe)
+		return 0;
+
+	return zpci_hot_reset_device(zdev);
+}
+
 static int get_power_status(struct hotplug_slot *hotplug_slot, u8 *value)
 {
 	struct zpci_dev *zdev = container_of(hotplug_slot, struct zpci_dev,
@@ -76,6 +99,7 @@ static int get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value)
 static const struct hotplug_slot_ops s390_hotplug_slot_ops = {
 	.enable_slot =		enable_slot,
 	.disable_slot =		disable_slot,
+	.reset_slot =		reset_slot,
 	.get_power_status =	get_power_status,
 	.get_adapter_status =	get_adapter_status,
 };