net: mscc: ocelot: issue a warning if stats are incorrectly ordered

Ocelot uses regmap_bulk_read() operations to efficiently read stats
registers. Currently the implementation relies on the stats layout to be
ordered to be most efficient.

Issue a warning if any future implementations happen to break this pattern.
Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
Co-developed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/mscc/ocelot_stats.c

@@ -602,7 +602,7 @@ EXPORT_SYMBOL(ocelot_port_get_stats64);
 static int ocelot_prepare_stats_regions(struct ocelot *ocelot)
 {
 	struct ocelot_stats_region *region = NULL;
-	unsigned int last;
+	unsigned int last = 0;
 	int i;
 
 	INIT_LIST_HEAD(&ocelot->stats_regions);
@@ -619,6 +619,12 @@ static int ocelot_prepare_stats_regions(struct ocelot *ocelot)
 			if (!region)
 				return -ENOMEM;
 
+			/* enum ocelot_stat must be kept sorted in the same
+			 * order as ocelot_stats_layout[i].reg in order to have
+			 * efficient bulking
+			 */
+			WARN_ON(last >= ocelot_stats_layout[i].reg);
+
 			region->base = ocelot_stats_layout[i].reg;
 			region->count = 1;
 			list_add_tail(&region->node, &ocelot->stats_regions);