SoC: rockchip: rockchip_max98090: Enable MICBIAS for headset keypress detection

The TS3A227E says that the headset keypress detection needs the MICBIAS
power in order to report the key events to ensure proper operation
The headset keypress detection needs the MICBIAS power in order to report
the key events all the time as long as MIC is present. So MICBIAS pin
is forced on when a MICROPHONE is detected.

On Veyron Minnie I observed that if the MICBIAS power is not present and
the key press detection is activated (just because it is enabled when you
insert a headset), it randomly reports a keypress on insert.
E.g. (KEY_PLAYPAUSE)

 Event: (SW_HEADPHONE_INSERT), value 1
 Event: (SW_MICROPHONE_INSERT), value 1
 Event: -------------- SYN_REPORT ------------
 Event: (KEY_PLAYPAUSE), value 1

Userspace thinks that KEY_PLAYPAUSE is pressed and produces the annoying
effect that the media player starts a play/pause loop.

Note that, although most of the time the key reported is the one
associated with BTN_0, not always this is true. On my tests I also saw
different keys reported
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Link: https://lore.kernel.org/r/20190719173929.24065-1-enric.balletbo@collabora.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/rockchip/rockchip_max98090.c

@@ -61,6 +61,37 @@ static const struct snd_kcontrol_new rk_mc_controls[] = {
 	SOC_DAPM_PIN_SWITCH("Speaker"),
 };
 
+static int rk_jack_event(struct notifier_block *nb, unsigned long event,
+			 void *data)
+{
+	struct snd_soc_jack *jack = (struct snd_soc_jack *)data;
+	struct snd_soc_dapm_context *dapm = &jack->card->dapm;
+
+	if (event & SND_JACK_MICROPHONE)
+		snd_soc_dapm_force_enable_pin(dapm, "MICBIAS");
+	else
+		snd_soc_dapm_disable_pin(dapm, "MICBIAS");
+
+	snd_soc_dapm_sync(dapm);
+
+	return 0;
+}
+
+static struct notifier_block rk_jack_nb = {
+	.notifier_call = rk_jack_event,
+};
+
+static int rk_init(struct snd_soc_pcm_runtime *runtime)
+{
+	/*
+	 * The jack has already been created in the rk_98090_headset_init()
+	 * function.
+	 */
+	snd_soc_jack_notifier_register(&headset_jack, &rk_jack_nb);
+
+	return 0;
+}
+
 static int rk_aif1_hw_params(struct snd_pcm_substream *substream,
 			     struct snd_pcm_hw_params *params)
 {
@@ -119,6 +150,7 @@ SND_SOC_DAILINK_DEFS(hifi,
 static struct snd_soc_dai_link rk_dailink = {
 	.name = "max98090",
 	.stream_name = "Audio",
+	.init = rk_init,
 	.ops = &rk_aif1_ops,
 	/* set max98090 as slave */
 	.dai_fmt = SND_SOC_DAIFMT_I2S | SND_SOC_DAIFMT_NB_NF |