ufshci: reserve one queue entry for an admin request

This patch reduces num_entries by 1 to reserve a admin slot. It
resolves the issue where admin requests cannot be executed
during QD32 because all queue entries are used.

It also resolve the issue of accessing the queue before it is
created by moving the queue construct point to before interrupt
enable.

Sponsored by:           Samsung Electronic
Reviewed by:		imp
Differential Revision:	https://reviews.freebsd.org/D51894

Author: jaeyoon-choi

sys/dev/ufshci/ufshci_ctrlr.c

@@ -146,6 +146,16 @@ ufshci_ctrlr_construct(struct ufshci_controller *ctrlr, device_t dev)
 		return (ENXIO);
 	}
 
+	/* Allocate and initialize UTP Task Management Request List. */
+	error = ufshci_utmr_req_queue_construct(ctrlr);
+	if (error)
+		return (error);
+
+	/* Allocate and initialize UTP Transfer Request List or SQ/CQ. */
+	error = ufshci_utr_req_queue_construct(ctrlr);
+	if (error)
+		return (error);
+
 	/* Enable additional interrupts by programming the IE register. */
 	ie = ufshci_mmio_read_4(ctrlr, ie);
 	ie |= UFSHCIM(UFSHCI_IE_REG_UTRCE);  /* UTR Completion */
@@ -160,19 +170,12 @@ ufshci_ctrlr_construct(struct ufshci_controller *ctrlr, device_t dev)
 
 	/* TODO: Initialize interrupt Aggregation Control Register (UTRIACR) */
 
-	/* Allocate and initialize UTP Task Management Request List. */
-	error = ufshci_utmr_req_queue_construct(ctrlr);
-	if (error)
-		return (error);
-
-	/* Allocate and initialize UTP Transfer Request List or SQ/CQ. */
-	error = ufshci_utr_req_queue_construct(ctrlr);
-	if (error)
-		return (error);
-
 	/* TODO: Separate IO and Admin slot */
-	/* max_hw_pend_io is the number of slots in the transfer_req_queue */
-	ctrlr->max_hw_pend_io = ctrlr->transfer_req_queue.num_entries;
+	/*
+	 * max_hw_pend_io is the number of slots in the transfer_req_queue.
+	 * Reduce num_entries by one to reserve an admin slot.
+	 */
+	ctrlr->max_hw_pend_io = ctrlr->transfer_req_queue.num_entries - 1;
 
 	return (0);
 }