ASoC: SOF: topology: fix: handle DAI widget connections properly with multiple CPU DAI's

Currently, when connecting a DAI widget to the BE CPU DAI, we overwrite
the previous connections. This worked because we only ever had 1 CPU DAI
for each rtd until now. But with multiple CPU DAI's, a new connection
between a BE CPU DAI and the DAI widget should be established without
affecting the previous connections. So, modify the loop to set the
playback/capture widget for the first BE CPU DAI that does not have a
connection established previously.

Fixes: 4a7e26a4d833 ("ASoC: SOF: topology: connect dai widget to all
cpu-dais")
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Link: https://lore.kernel.org/r/20200415202816.934-2-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/topology.c

@@ -1257,15 +1257,45 @@ static int sof_connect_dai_widget(struct snd_soc_component *scomp,
 
 		switch (w->id) {
 		case snd_soc_dapm_dai_out:
-			for_each_rtd_cpu_dais(rtd, i, cpu_dai)
+			for_each_rtd_cpu_dais(rtd, i, cpu_dai) {
+				/*
+				 * Please create DAI widget in the right order
+				 * to ensure BE will connect to the right DAI
+				 * widget.
+				 */
+				if (!cpu_dai->capture_widget) {
 					cpu_dai->capture_widget = w;
+					break;
+				}
+			}
+			if (i == rtd->num_cpus) {
+				dev_err(scomp->dev, "error: can't find BE for DAI %s\n",
+					w->name);
+
+				return -EINVAL;
+			}
 			dai->name = rtd->dai_link->name;
 			dev_dbg(scomp->dev, "tplg: connected widget %s -> DAI link %s\n",
 				w->name, rtd->dai_link->name);
 			break;
 		case snd_soc_dapm_dai_in:
-			for_each_rtd_cpu_dais(rtd, i, cpu_dai)
+			for_each_rtd_cpu_dais(rtd, i, cpu_dai) {
+				/*
+				 * Please create DAI widget in the right order
+				 * to ensure BE will connect to the right DAI
+				 * widget.
+				 */
+				if (!cpu_dai->playback_widget) {
 					cpu_dai->playback_widget = w;
+					break;
+				}
+			}
+			if (i == rtd->num_cpus) {
+				dev_err(scomp->dev, "error: can't find BE for DAI %s\n",
+					w->name);
+
+				return -EINVAL;
+			}
 			dai->name = rtd->dai_link->name;
 			dev_dbg(scomp->dev, "tplg: connected widget %s -> DAI link %s\n",
 				w->name, rtd->dai_link->name);