irqchip/gicv3-its: Add a new function for parsing device table BASERn

Only the device table BASERn needs to be handled differently as
compared to all other tables. So, adding a separate function for
easy code maintenance and improved code readability.
Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-gic-v3-its.c

@@ -840,6 +840,30 @@ static void its_write_baser(struct its_node *its, struct its_baser *baser,
 	baser->val = its_read_baser(its, baser);
 }
 
+static void its_parse_baser_device(struct its_node *its, struct its_baser *baser,
+				   u32 *order)
+{
+	u64 esz = GITS_BASER_ENTRY_SIZE(its_read_baser(its, baser));
+	u32 ids = its->device_ids;
+	u32 new_order = *order;
+
+	/*
+	 * Allocate as many entries as required to fit the
+	 * range of device IDs that the ITS can grok... The ID
+	 * space being incredibly sparse, this results in a
+	 * massive waste of memory.
+	 */
+	new_order = max_t(u32, get_order(esz << ids), new_order);
+	if (new_order >= MAX_ORDER) {
+		new_order = MAX_ORDER - 1;
+		ids = ilog2(PAGE_ORDER_TO_SIZE(new_order) / esz);
+		pr_warn("ITS@%pa: Device Table too large, reduce ids %u->%u\n",
+			&its->phys_base, its->device_ids, ids);
+	}
+
+	*order = new_order;
+}
+
 static void its_free_tables(struct its_node *its)
 {
 	int i;
@@ -891,29 +915,8 @@ static int its_alloc_tables(const char *node_name, struct its_node *its)
 		if (type == GITS_BASER_TYPE_NONE)
 			continue;
 
-		/*
-		 * Allocate as many entries as required to fit the
-		 * range of device IDs that the ITS can grok... The ID
-		 * space being incredibly sparse, this results in a
-		 * massive waste of memory.
-		 *
-		 * For other tables, only allocate a single page.
-		 */
-		if (type == GITS_BASER_TYPE_DEVICE) {
-			/*
-			 * 'order' was initialized earlier to the default page
-			 * granule of the the ITS.  We can't have an allocation
-			 * smaller than that.  If the requested allocation
-			 * is smaller, round up to the default page granule.
-			 */
-			order = max(get_order((1UL << ids) * entry_size),
-				    order);
-			if (order >= MAX_ORDER) {
-				order = MAX_ORDER - 1;
-				pr_warn("%s: Device Table too large, reduce its page order to %u\n",
-					node_name, order);
-			}
-		}
+		if (type == GITS_BASER_TYPE_DEVICE)
+			its_parse_baser_device(its, baser, &order);
 
 retry_alloc_baser:
 		alloc_pages = (PAGE_ORDER_TO_SIZE(order) / psz);