ALSA: hda - stop setup_dig_out_stream() causing clicks

Starting audio or seeking in various music players causes
setup_dig_out_stream() to be called, which resets the SPDIF stream,
which caused one DAC (but not another) to make a clicking noise every
time.

This patch ensures the reset only happens when it needs to, which is
when the format changes, and makes the code a little more readable.
Signed-off-by: Laurence Darby <ldarby@tuffmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_codec.c

@@ -4816,10 +4816,20 @@ EXPORT_SYMBOL_HDA(snd_hda_input_mux_put);
 static void setup_dig_out_stream(struct hda_codec *codec, hda_nid_t nid,
 				 unsigned int stream_tag, unsigned int format)
 {
-	struct hda_spdif_out *spdif = snd_hda_spdif_out_of_nid(codec, nid);
+	struct hda_spdif_out *spdif;
+	unsigned int curr_fmt;
+	bool reset;
+
+	spdif = snd_hda_spdif_out_of_nid(codec, nid);
+	curr_fmt = snd_hda_codec_read(codec, nid, 0,
+				      AC_VERB_GET_STREAM_FORMAT, 0);
+	reset = codec->spdif_status_reset &&
+		(spdif->ctls & AC_DIG1_ENABLE) &&
+		curr_fmt != format;
 
-	/* turn off SPDIF once; otherwise the IEC958 bits won't be updated */
-	if (codec->spdif_status_reset && (spdif->ctls & AC_DIG1_ENABLE))
+	/* turn off SPDIF if needed; otherwise the IEC958 bits won't be
+	   updated */
+	if (reset)
 		set_dig_out_convert(codec, nid,
 				    spdif->ctls & ~AC_DIG1_ENABLE & 0xff,
 				    -1);
@@ -4831,7 +4841,7 @@ static void setup_dig_out_stream(struct hda_codec *codec, hda_nid_t nid,
 						   format);
 	}
 	/* turn on again (if needed) */
-	if (codec->spdif_status_reset && (spdif->ctls & AC_DIG1_ENABLE))
+	if (reset)
 		set_dig_out_convert(codec, nid,
 				    spdif->ctls & 0xff, -1);
 }