bnxt_en: Allow the user to set ethtool stats-block-usecs to 0.

For debugging purpose, it is sometimes useful to disable periodic
port statistics updates, so that the firmware logs will not be
filled with statistics update messages.
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnxt/bnxt.c

@@ -6843,7 +6843,8 @@ static void bnxt_timer(unsigned long data)
 	if (atomic_read(&bp->intr_sem) != 0)
 		goto bnxt_restart_timer;
 
-	if (bp->link_info.link_up && (bp->flags & BNXT_FLAG_PORT_STATS)) {
+	if (bp->link_info.link_up && (bp->flags & BNXT_FLAG_PORT_STATS) &&
+	    bp->stats_coal_ticks) {
 		set_bit(BNXT_PERIODIC_STATS_SP_EVENT, &bp->sp_event);
 		schedule_work(&bp->sp_task);
 	}

drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c

@@ -86,9 +86,11 @@ static int bnxt_set_coalesce(struct net_device *dev,
 	if (bp->stats_coal_ticks != coal->stats_block_coalesce_usecs) {
 		u32 stats_ticks = coal->stats_block_coalesce_usecs;
 
-		stats_ticks = clamp_t(u32, stats_ticks,
-				      BNXT_MIN_STATS_COAL_TICKS,
-				      BNXT_MAX_STATS_COAL_TICKS);
+		/* Allow 0, which means disable. */
+		if (stats_ticks)
+			stats_ticks = clamp_t(u32, stats_ticks,
+					      BNXT_MIN_STATS_COAL_TICKS,
+					      BNXT_MAX_STATS_COAL_TICKS);
 		stats_ticks = rounddown(stats_ticks, BNXT_MIN_STATS_COAL_TICKS);
 		bp->stats_coal_ticks = stats_ticks;
 		update_stats = true;