Input: wm97xx-core - add retries to wm97xx_read_aux_adc

Add logic to wm97xx_read_aux_adc() to retry reading the adc if the
sample failed.  This could occur if the previous sample was still in
the return register or the sample timed-out.  Also avoid a pathologic
failure mode by disabling the digitizer and returning -EBUSY after 5
retries.

Signed-off-by: Eric Millbrandt <emillbrandt@dekaresearch.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/touchscreen/wm97xx-core.c

@@ -125,6 +125,8 @@ int wm97xx_read_aux_adc(struct wm97xx *wm, u16 adcsel)
 {
 	int power_adc = 0, auxval;
 	u16 power = 0;
+	int rc = 0;
+	int timeout = 0;
 
 	/* get codec */
 	mutex_lock(&wm->codec_mutex);
@@ -143,7 +145,9 @@ int wm97xx_read_aux_adc(struct wm97xx *wm, u16 adcsel)
 
 	/* Turn polling mode on to read AUX ADC */
 	wm->pen_probably_down = 1;
-	wm->codec->poll_sample(wm, adcsel, &auxval);
+
+	while (rc != RC_VALID && timeout++ < 5)
+		rc = wm->codec->poll_sample(wm, adcsel, &auxval);
 
 	if (power_adc)
 		wm97xx_reg_write(wm, AC97_EXTENDED_MID, power | 0x8000);
@@ -152,8 +156,15 @@ int wm97xx_read_aux_adc(struct wm97xx *wm, u16 adcsel)
 
 	wm->pen_probably_down = 0;
 
+	if (timeout >= 5) {
+		dev_err(wm->dev,
+			"timeout reading auxadc %d, disabling digitiser\n",
+			adcsel);
+		wm->codec->dig_enable(wm, false);
+	}
+
 	mutex_unlock(&wm->codec_mutex);
-	return auxval & 0xfff;
+	return (rc == RC_VALID ? auxval & 0xfff : -EBUSY);
 }
 EXPORT_SYMBOL_GPL(wm97xx_read_aux_adc);