ASoC: wm8994: Support external capacitors on MICBIAS2 with jack detection

When an external capacitor is connected to MICBIAS2 on devices with
jack detection (which is not required but may be done in some systems)
then the loading may mean that better performance is obtained when
the microphone bias is enabled normally rather than using the low power
mode. Provide platform data allowing systems to indicate if they require
this.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

include/linux/mfd/wm8994/pdata.h

@@ -185,6 +185,9 @@ struct wm8994_pdata {
         unsigned int jd_scthr:2;
         unsigned int jd_thr:2;
 
+	/* Configure WM1811 jack detection for use with external capacitor */
+	unsigned int jd_ext_cap:1;
+
 	/* WM8958 microphone bias configuration */
 	int micbias[2];
 

sound/soc/codecs/wm8994.c

@@ -3172,6 +3172,14 @@ static void wm8958_default_micdet(u16 status, void *data)
 
 			wm1811_jackdet_set_mode(codec,
 						WM1811_JACKDET_MODE_JACK);
+
+			if (wm8994->pdata->jd_ext_cap) {
+				mutex_lock(&codec->mutex);
+				snd_soc_dapm_disable_pin(&codec->dapm,
+							 "MICBIAS2");
+				snd_soc_dapm_sync(&codec->dapm);
+				mutex_unlock(&codec->mutex);
+			}
 		}
 	}
 
@@ -3227,6 +3235,15 @@ static irqreturn_t wm1811_jackdet_irq(int irq, void *data)
 		snd_soc_update_bits(codec, WM8958_MICBIAS2,
 				    WM8958_MICB2_DISCH, 0);
 
+		/* If required for an external cap force MICBIAS on */
+		if (wm8994->pdata->jd_ext_cap) {
+			mutex_lock(&codec->mutex);
+			snd_soc_dapm_force_enable_pin(&codec->dapm,
+						      "MICBIAS2");
+			snd_soc_dapm_sync(&codec->dapm);
+			mutex_unlock(&codec->mutex);
+		}
+
 		/*
 		 * Start off measument of microphone impedence to find
 		 * out what's actually there.
@@ -3241,6 +3258,13 @@ static irqreturn_t wm1811_jackdet_irq(int irq, void *data)
 		snd_soc_update_bits(codec, WM8958_MICBIAS2,
 				    WM8958_MICB2_DISCH, WM8958_MICB2_DISCH);
 
+		if (wm8994->pdata->jd_ext_cap) {
+			mutex_lock(&codec->mutex);
+			snd_soc_dapm_disable_pin(&codec->dapm, "MICBIAS2");
+			snd_soc_dapm_sync(&codec->dapm);
+			mutex_unlock(&codec->mutex);
+		}
+
 		snd_soc_jack_report(wm8994->micdet[0].jack, 0,
 				    SND_JACK_MECHANICAL | SND_JACK_HEADSET |
 				    wm8994->btn_mask);