scsi: mpi3mr: Allow certain commands during pci-remove hook

Instead of driver returning DID_NO_CONNECT during driver unload allow SSU
and Sync Cache commands to be sent to the controller to flush any cached
data from the drive.

Link: https://lore.kernel.org/r/20210520152545.2710479-16-kashyap.desai@broadcom.com
Cc: sathya.prakash@broadcom.com
Reviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NTomas Henzl <thenzl@redhat.com>
Reviewed-by: NHimanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: NKashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/mpi3mr/mpi3mr_os.c

@@ -2767,6 +2767,26 @@ static int mpi3mr_target_alloc(struct scsi_target *starget)
 	return retval;
 }
 
+/**
+ * mpi3mr_allow_scmd_to_fw - Command is allowed during shutdown
+ * @scmd: SCSI Command reference
+ *
+ * Checks whether a cdb is allowed during shutdown or not.
+ *
+ * Return: TRUE for allowed commands, FALSE otherwise.
+ */
+
+inline bool mpi3mr_allow_scmd_to_fw(struct scsi_cmnd *scmd)
+{
+	switch (scmd->cmnd[0]) {
+	case SYNCHRONIZE_CACHE:
+	case START_STOP:
+		return true;
+	default:
+		return false;
+	}
+}
+
 /**
  * mpi3mr_qcmd - I/O request despatcher
  * @shost: SCSI Host reference
@@ -2802,7 +2822,8 @@ static int mpi3mr_qcmd(struct Scsi_Host *shost,
 		goto out;
 	}
 
-	if (mrioc->stop_drv_processing) {
+	if (mrioc->stop_drv_processing &&
+	    !(mpi3mr_allow_scmd_to_fw(scmd))) {
 		scmd->result = DID_NO_CONNECT << 16;
 		scmd->scsi_done(scmd);
 		goto out;