ASoC: wm8994: Enabling VMID should take a runtime PM reference

We can enable VMID independently of the bias in some use cases so we need
to ensure that the core device is powered up.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@vger.kernel.org

sound/soc/codecs/wm8994.c

@@ -770,6 +770,8 @@ static void vmid_reference(struct snd_soc_codec *codec)
 {
 	struct wm8994_priv *wm8994 = snd_soc_codec_get_drvdata(codec);
 
+	pm_runtime_get_sync(codec->dev);
+
 	wm8994->vmid_refcount++;
 
 	dev_dbg(codec->dev, "Referencing VMID, refcount is now %d\n",
@@ -837,6 +839,8 @@ static void vmid_dereference(struct snd_soc_codec *codec)
 				    WM8994_VMID_BUF_ENA |
 				    WM8994_VMID_RAMP_MASK, 0);
 	}
+
+	pm_runtime_put(codec->dev);
 }
 
 static int vmid_event(struct snd_soc_dapm_widget *w,