extcon: arizona: Check we report a valid impedance

Occasionally we can trigger an interrupt before we have completed
impedance measurement, although the valid bit will still be set. This
patch spins reading the impedance value until a valid value is seen.
Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/extcon/extcon-arizona.c

@@ -737,11 +737,12 @@ static irqreturn_t arizona_micdet(int irq, void *data)
 {
 	struct arizona_extcon_info *info = data;
 	struct arizona *arizona = info->arizona;
-	unsigned int val, lvl;
+	unsigned int val = 0, lvl;
 	int ret, i, key;
 
 	mutex_lock(&info->lock);
 
+	for (i = 0; i < 10 && !(val & 0x7fc); i++) {
 		ret = regmap_read(arizona->regmap, ARIZONA_MIC_DETECT_3, &val);
 		if (ret != 0) {
 			dev_err(arizona->dev, "Failed to read MICDET: %d\n", ret);
@@ -756,6 +757,13 @@ static irqreturn_t arizona_micdet(int irq, void *data)
 			mutex_unlock(&info->lock);
 			return IRQ_NONE;
 		}
+	}
+
+	if (i == 10 && !(val & 0x7fc)) {
+		dev_err(arizona->dev, "Failed to get valid MICDET value\n");
+		mutex_unlock(&info->lock);
+		return IRQ_NONE;
+	}
 
 	/* Due to jack detect this should never happen */
 	if (!(val & ARIZONA_MICD_STS)) {