soundwire: bus: test read status

In the existing code we may read a negative error value but still mask
it and write it back.

Make sure all reads are tested and errors not propagated further.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://lore.kernel.org/r/20210302091122.13952-3-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/soundwire/bus.c

@@ -875,8 +875,12 @@ static int sdw_slave_clk_stop_prepare(struct sdw_slave *slave,
 		if (wake_en)
 			val |= SDW_SCP_SYSTEMCTRL_WAKE_UP_EN;
 	} else {
-		val = sdw_read_no_pm(slave, SDW_SCP_SYSTEMCTRL);
-
+		ret = sdw_read_no_pm(slave, SDW_SCP_SYSTEMCTRL);
+		if (ret < 0) {
+			dev_err(&slave->dev, "SDW_SCP_SYSTEMCTRL read failed:%d\n", ret);
+			return ret;
+		}
+		val = ret;
 		val &= ~(SDW_SCP_SYSTEMCTRL_CLK_STP_PREP);
 	}
 
@@ -895,8 +899,12 @@ static int sdw_bus_wait_for_clk_prep_deprep(struct sdw_bus *bus, u16 dev_num)
 	int val;
 
 	do {
-		val = sdw_bread_no_pm(bus, dev_num, SDW_SCP_STAT) &
-			SDW_SCP_STAT_CLK_STP_NF;
+		val = sdw_bread_no_pm(bus, dev_num, SDW_SCP_STAT);
+		if (val < 0) {
+			dev_err(bus->dev, "SDW_SCP_STAT bread failed:%d\n", val);
+			return val;
+		}
+		val &= SDW_SCP_STAT_CLK_STP_NF;
 		if (!val) {
 			dev_info(bus->dev, "clock stop prep/de-prep done slave:%d",
 				 dev_num);