ALSA: hda - Reduce click noise at power-saving

Add some tricks to reduce the click noise at powering down to D3
in the power saving mode on STAC/IDT codecs.
The key seems to be to reset PINs before the power-down, and some
delay before entering D3.  The needed delay is significantly long,
but I don't know why.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_codec.c

@@ -2367,9 +2367,14 @@ static void hda_set_power_state(struct hda_codec *codec, hda_nid_t fg,
 	hda_nid_t nid;
 	int i;
 
-	snd_hda_codec_write(codec, fg, 0, AC_VERB_SET_POWER_STATE,
+	/* this delay seems necessary to avoid click noise at power-down */
+	if (power_state == AC_PWRST_D3)
+		msleep(100);
+	snd_hda_codec_read(codec, fg, 0, AC_VERB_SET_POWER_STATE,
 			    power_state);
-	msleep(10); /* partial workaround for "azx_get_response timeout" */
+	/* partial workaround for "azx_get_response timeout" */
+	if (power_state == AC_PWRST_D0)
+		msleep(10);
 
 	nid = codec->start_nid;
 	for (i = 0; i < codec->num_nodes; i++, nid++) {

sound/pci/hda/patch_sigmatel.c

@@ -4745,6 +4745,20 @@ static int stac92xx_hp_check_power_status(struct hda_codec *codec,
 static int stac92xx_suspend(struct hda_codec *codec, pm_message_t state)
 {
 	struct sigmatel_spec *spec = codec->spec;
+	int i;
+	hda_nid_t nid;
+
+	/* reset each pin before powering down DAC/ADC to avoid click noise */
+	nid = codec->start_nid;
+	for (i = 0; i < codec->num_nodes; i++, nid++) {
+		unsigned int wcaps = get_wcaps(codec, nid);
+		unsigned int wid_type = (wcaps & AC_WCAP_TYPE) >>
+			AC_WCAP_TYPE_SHIFT;
+		if (wid_type == AC_WID_PIN)
+			snd_hda_codec_read(codec, nid, 0,
+				AC_VERB_SET_PIN_WIDGET_CONTROL, 0);
+	}
+
 	if (spec->eapd_mask)
 		stac_gpio_set(codec, spec->gpio_mask,
 				spec->gpio_dir, spec->gpio_data &