PCI: Notify driver before and after device reset

Notify a PCI device driver when its device's access is about to be disabled
for an impending reset attempt, then after the attempt completes and device
access is restored.  The notification is via the pci_error_handlers
interface.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci.c

@@ -3305,8 +3305,27 @@ static void pci_dev_unlock(struct pci_dev *dev)
 	pci_cfg_access_unlock(dev);
 }
 
+/**
+ * pci_reset_notify - notify device driver of reset
+ * @dev: device to be notified of reset
+ * @prepare: 'true' if device is about to be reset; 'false' if reset attempt
+ *           completed
+ *
+ * Must be called prior to device access being disabled and after device
+ * access is restored.
+ */
+static void pci_reset_notify(struct pci_dev *dev, bool prepare)
+{
+	const struct pci_error_handlers *err_handler =
+			dev->driver ? dev->driver->err_handler : NULL;
+	if (err_handler && err_handler->reset_notify)
+		err_handler->reset_notify(dev, prepare);
+}
+
 static void pci_dev_save_and_disable(struct pci_dev *dev)
 {
+	pci_reset_notify(dev, true);
+
 	/*
 	 * Wake-up device prior to save.  PM registers default to D0 after
 	 * reset and a simple register restore doesn't reliably return
@@ -3328,6 +3347,7 @@ static void pci_dev_save_and_disable(struct pci_dev *dev)
 static void pci_dev_restore(struct pci_dev *dev)
 {
 	pci_restore_state(dev);
+	pci_reset_notify(dev, false);
 }
 
 static int pci_dev_reset(struct pci_dev *dev, int probe)
@@ -3344,6 +3364,7 @@ static int pci_dev_reset(struct pci_dev *dev, int probe)
 
 	return rc;
 }
+
 /**
  * __pci_reset_function - reset a PCI device function
  * @dev: PCI device to reset

include/linux/pci.h

@@ -603,6 +603,9 @@ struct pci_error_handlers {
 	/* PCI slot has been reset */
 	pci_ers_result_t (*slot_reset)(struct pci_dev *dev);
 
+	/* PCI function reset prepare or completed */
+	void (*reset_notify)(struct pci_dev *dev, bool prepare);
+
 	/* Device driver may resume normal operations */
 	void (*resume)(struct pci_dev *dev);
 };