soundwire: return earlier if no slave is attached

If there is no slave attached to soundwire bus, we
can return earlier from sdw_bus_prep_clk_stop() and
sdw_bus_exit_clk_stop(), this saves a redundant value
check.
Signed-off-by: Chao Song <chao.song@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20210126085439.4349-1-yung-chuan.liao@linux.intel.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/soundwire/bus.c

@@ -951,17 +951,17 @@ int sdw_bus_prep_clk_stop(struct sdw_bus *bus)
 			simple_clk_stop = false;
 	}
 
-	if (is_slave && !simple_clk_stop) {
+	/* Skip remaining clock stop preparation if no Slave is attached */
+	if (!is_slave)
+		return ret;
+
+	if (!simple_clk_stop) {
 		ret = sdw_bus_wait_for_clk_prep_deprep(bus,
 						       SDW_BROADCAST_DEV_NUM);
 		if (ret < 0)
 			return ret;
 	}
 
-	/* Don't need to inform slaves if there is no slave attached */
-	if (!is_slave)
-		return ret;
-
 	/* Inform slaves that prep is done */
 	list_for_each_entry(slave, &bus->slaves, node) {
 		if (!slave->dev_num)
@@ -1075,16 +1075,13 @@ int sdw_bus_exit_clk_stop(struct sdw_bus *bus)
 				 "clk stop deprep failed:%d", ret);
 	}
 
-	if (is_slave && !simple_clk_stop)
-		sdw_bus_wait_for_clk_prep_deprep(bus, SDW_BROADCAST_DEV_NUM);
-
-	/*
-	 * Don't need to call slave callback function if there is no slave
-	 * attached
-	 */
+	/* Skip remaining clock stop de-preparation if no Slave is attached */
 	if (!is_slave)
 		return 0;
 
+	if (!simple_clk_stop)
+		sdw_bus_wait_for_clk_prep_deprep(bus, SDW_BROADCAST_DEV_NUM);
+
 	list_for_each_entry(slave, &bus->slaves, node) {
 		if (!slave->dev_num)
 			continue;