ASoC: wm8994: Provide VMID mode control and fix default sequence

The optimal management of VMID depends on a number of factors which vary
dynamically at runtime, for example the connection to a system docking
station. In some circumstances it is desirable to keep VMID enabled all
the time, in others it is desirable to aggressively power it up and down.

Provide a callback allowing machine driver to configure either the normal
power up/down mode (WM8994_VMID_MODE_NORMAL) or to maintain VMID even
when idle (WM8994_VMID_MODE_FORCE). This callback, wm8994_vmid_mode(),
should be called with the CODEC lock.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/wm8994.h b/sound/soc/codecs/wm8994.h
index 2f4d2d1..c724112 100644
--- a/sound/soc/codecs/wm8994.h
+++ b/sound/soc/codecs/wm8994.h
@@ -32,6 +32,11 @@
 #define WM8994_FLL_SRC_LRCLK  3
 #define WM8994_FLL_SRC_BCLK   4
 
+enum wm8994_vmid_mode {
+	WM8994_VMID_NORMAL,
+	WM8994_VMID_FORCE,
+};
+
 typedef void (*wm8958_micdet_cb)(u16 status, void *data);
 
 int wm8994_mic_detect(struct snd_soc_codec *codec, struct snd_soc_jack *jack,
@@ -39,6 +44,8 @@
 int wm8958_mic_detect(struct snd_soc_codec *codec, struct snd_soc_jack *jack,
 		      wm8958_micdet_cb cb, void *cb_data);
 
+int wm8994_vmid_mode(struct snd_soc_codec *codec, enum wm8994_vmid_mode mode);
+
 int wm8958_aif_ev(struct snd_soc_dapm_widget *w,
 		  struct snd_kcontrol *kcontrol, int event);
 
@@ -75,6 +82,7 @@
 
 	int vmid_refcount;
 	int active_refcount;
+	enum wm8994_vmid_mode vmid_mode;
 
 	int dac_rates[2];
 	int lrclk_shared[2];