scsi: ufs: mcq: Prevent no I/O queue case for MCQ

If hba_maxq equals poll_queues, which means there are no I/O queues
(HCTX_TYPE_DEFAULT, HCTX_TYPE_READ), the very first hw queue will be
allocated as HCTX_TYPE_POLL and it will be used as the dev_cmd_queue.  In
this case, device commands such as QUERY cannot be properly handled.

This patch prevents the initialization of MCQ when the number of I/O queues
is not set and only the number of POLL queues is set.

Signed-off-by: Minwoo Im <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>

Author: minwooim

drivers/ufs/core/ufs-mcq.c

@@ -179,6 +179,15 @@ static int ufshcd_mcq_config_nr_queues(struct ufs_hba *hba)
 		return -EOPNOTSUPP;
 	}
 
+	/*
+	 * Device should support at least one I/O queue to handle device
+	 * commands via hba->dev_cmd_queue.
+	 */
+	if (hba_maxq == poll_queues) {
+		dev_err(hba->dev, "At least one non-poll queue required\n");
+		return -EOPNOTSUPP;
+	}
+
 	rem = hba_maxq;
 
 	if (rw_queues) {