scsi: qedf: Fix firmware halt over suspend and resume

While performing certain power-off sequences, PCI drivers are called to
suspend and resume their underlying devices through PCI PM (power
management) interface. However the hardware does not support PCI PM
suspend/resume operations so system wide suspend/resume leads to bad MFW
(management firmware) state which causes various follow-up errors in driver
when communicating with the device/firmware.

To fix this driver implements PCI PM suspend handler to indicate
unsupported operation to the PCI subsystem explicitly, thus avoiding system
to go into suspended/standby mode.

Fixes: 61d8658b4a43 ("scsi: qedf: Add QLogic FastLinQ offload FCoE driver framework.")
Signed-off-by: Saurav Kashyap <[e-mail]>
Signed-off-by: Nilesh Javali <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/qedf/qedf_main.c

···
 static void qedf_shutdown(struct pci_dev *pdev);
 static void qedf_schedule_recovery_handler(void *dev);
 static void qedf_recovery_handler(struct work_struct *work);
+static int qedf_suspend(struct pci_dev *pdev, pm_message_t state);
 
 /*
  * Driver module parameters.
···
 	.probe = qedf_probe,
 	.remove = qedf_remove,
 	.shutdown = qedf_shutdown,
+	.suspend = qedf_suspend,
 };
 
 static int __qedf_probe(struct pci_dev *pdev, int mode)
···
 static void qedf_shutdown(struct pci_dev *pdev)
 {
 	__qedf_remove(pdev, QEDF_MODE_NORMAL);
+}
+
+static int qedf_suspend(struct pci_dev *pdev, pm_message_t state)
+{
+	struct qedf_ctx *qedf;
+
+	if (!pdev) {
+		QEDF_ERR(NULL, "pdev is NULL.\n");
+		return -ENODEV;
+	}
+
+	qedf = pci_get_drvdata(pdev);
+
+	QEDF_ERR(&qedf->dbg_ctx, "%s: Device does not support suspend operation\n", __func__);
+
+	return -EPERM;
 }
 
 /*