ASoC: Ensure we get an impedence reported for WM8958 jack detect

Occasionally we may see an accessory reported before we have a stable
impedance for the accessory. If this happens then reread the status in
order to ensure that the handler can take the appropriate action for the
status change.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

include/linux/mfd/wm8994/registers.h

@@ -1962,6 +1962,21 @@
 #define WM8958_MICB2_DISCH_SHIFT                     0  /* MICB2_DISCH */
 #define WM8958_MICB2_DISCH_WIDTH                     1  /* MICB2_DISCH */
 
+/*
+ * R210 (0xD2) - Mic Detect 3
+ */
+#define WM8958_MICD_LVL_MASK                    0x07FC  /* MICD_LVL - [10:2] */
+#define WM8958_MICD_LVL_SHIFT                        2  /* MICD_LVL - [10:2] */
+#define WM8958_MICD_LVL_WIDTH                        9  /* MICD_LVL - [10:2] */
+#define WM8958_MICD_VALID                       0x0002  /* MICD_VALID */
+#define WM8958_MICD_VALID_MASK                  0x0002  /* MICD_VALID */
+#define WM8958_MICD_VALID_SHIFT                      1  /* MICD_VALID */
+#define WM8958_MICD_VALID_WIDTH                      1  /* MICD_VALID */
+#define WM8958_MICD_STS                         0x0001  /* MICD_STS */
+#define WM8958_MICD_STS_MASK                    0x0001  /* MICD_STS */
+#define WM8958_MICD_STS_SHIFT                        0  /* MICD_STS */
+#define WM8958_MICD_STS_WIDTH                        1  /* MICD_STS */
+
 /*
  * R76 (0x4C) - Charge Pump (1)
  */

sound/soc/codecs/wm8994.c

@@ -3030,11 +3030,17 @@ static irqreturn_t wm8958_mic_irq(int irq, void *data)
 {
 	struct wm8994_priv *wm8994 = data;
 	struct snd_soc_codec *codec = wm8994->codec;
-	int reg;
+	int reg, count;
 
+	/* We may occasionally read a detection without an impedence
+	 * range being provided - if that happens loop again.
+	 */
+	count = 10;
+	do {
 		reg = snd_soc_read(codec, WM8958_MIC_DETECT_3);
 		if (reg < 0) {
-		dev_err(codec->dev, "Failed to read mic detect status: %d\n",
+			dev_err(codec->dev,
+				"Failed to read mic detect status: %d\n",
 				reg);
 			return IRQ_NONE;
 		}
@@ -3044,6 +3050,15 @@ static irqreturn_t wm8958_mic_irq(int irq, void *data)
 			goto out;
 		}
 
+		if (!(reg & WM8958_MICD_STS) || (reg & WM8958_MICD_LVL_MASK))
+			break;
+
+		msleep(1);
+	} while (count--);
+
+	if (count == 0)
+		dev_warn(codec->dev, "No impedence range reported for jack\n");
+
 #ifndef CONFIG_SND_SOC_WM8994_MODULE
 	trace_snd_soc_jack_irq(dev_name(codec->dev));
 #endif