iio: adc: at91-sama5d2_adc: ensure backward compatibility with previous devices

Thermal management code might run on device with no OTP data (old
device). To ensure ADC is still probed in case no OTP data is found or
in case other failures appears when reading OTP data do not return error
codes on ADC probing from at91_adc_temp_sensor_init() but print an error
message and initialize accordingly st->temp_st.init. Also, to be sure no
clients of ADC temperature channel is succeding in requesting the
temperature channel take into account the initialization status of
temperature channel in channel request function (at91_adc_chan_xlate()).

Fixes: 3e87d89 ("iio: adc: at91-sama5d2_adc: add support for temperature sensor")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>

Author: claudiubeznea

drivers/iio/adc/at91-sama5d2_adc.c

@@ -446,6 +446,7 @@ static const struct at91_adc_reg_layout sama7g5_layout = {
  * @osr_mask:		oversampling ratio bitmask on EMR register
  * @osr_vals:		available oversampling rates
  * @chan_realbits:	realbits for registered channels
+ * @temp_chan:		temperature channel index
  * @temp_sensor:	temperature sensor supported
  */
 struct at91_adc_platform {
@@ -461,6 +462,7 @@ struct at91_adc_platform {
 	unsigned int				osr_mask;
 	unsigned int				osr_vals;
 	unsigned int				chan_realbits;
+	unsigned int				temp_chan;
 	bool					temp_sensor;
 };
 
@@ -743,15 +745,23 @@ static const struct at91_adc_platform sama7g5_platform = {
 		    BIT(AT91_SAMA5D2_EMR_OSR_256SAMPLES),
 	.chan_realbits = 16,
 	.temp_sensor = true,
+	.temp_chan = AT91_SAMA7G5_ADC_TEMP_CHANNEL,
 };
 
 static int at91_adc_chan_xlate(struct iio_dev *indio_dev, int chan)
 {
+	struct at91_adc_state *st = iio_priv(indio_dev);
 	int i;
 
 	for (i = 0; i < indio_dev->num_channels; i++) {
-		if (indio_dev->channels[i].scan_index == chan)
+		if (indio_dev->channels[i].scan_index == chan) {
+			if (st->soc_info.platform->temp_sensor &&
+			    chan == st->soc_info.platform->temp_chan &&
+			    !st->temp_st.init)
+				return -EINVAL;
+
 			return i;
+		}
 	}
 	return -EINVAL;
 }
@@ -2183,36 +2193,34 @@ static int at91_adc_buffer_and_trigger_init(struct device *dev,
 	return 0;
 }
 
-static int at91_adc_temp_sensor_init(struct iio_dev *indio_dev)
+static void at91_adc_temp_sensor_init(struct at91_adc_state *st,
+				      struct device *dev)
 {
-	struct at91_adc_state *st = iio_priv(indio_dev);
 	struct at91_adc_temp_sensor_clb *clb = &st->soc_info.temp_sensor_clb;
 	struct nvmem_cell *temp_calib;
 	u32 *buf;
 	size_t len;
-	int ret = 0;
 
 	if (!st->soc_info.platform->temp_sensor)
-		return 0;
+		return;
+
+	st->temp_st.init = false;
 
 	/* Get the calibration data from NVMEM. */
-	temp_calib = devm_nvmem_cell_get(indio_dev->dev.parent,
-					 "temperature_calib");
+	temp_calib = devm_nvmem_cell_get(dev, "temperature_calib");
 	if (IS_ERR(temp_calib)) {
-		ret = PTR_ERR(temp_calib);
-
-		if (ret == -ENOENT) {
-			st->temp_st.init = false;
-			return 0;
-		}
-		return ret;
+		if (PTR_ERR(temp_calib) != -ENOENT)
+			dev_err(dev, "Failed to get temperature_calib cell!\n");
+		return;
 	}
 
 	buf = nvmem_cell_read(temp_calib, &len);
-	if (IS_ERR(buf))
-		return PTR_ERR(buf);
+	if (IS_ERR(buf)) {
+		dev_err(dev, "Failed to read calibration data!\n");
+		return;
+	}
 	if (len < AT91_ADC_TS_CLB_IDX_MAX * 4) {
-		ret = -EINVAL;
+		dev_err(dev, "Invalid calibration data!\n");
 		goto free_buf;
 	}
 
@@ -2226,7 +2234,6 @@ static int at91_adc_temp_sensor_init(struct iio_dev *indio_dev)
 
 free_buf:
 	kfree(buf);
-	return ret;
 }
 
 static int at91_adc_probe(struct platform_device *pdev)
@@ -2362,9 +2369,7 @@ static int at91_adc_probe(struct platform_device *pdev)
 	if (ret)
 		goto vref_disable;
 
-	ret = at91_adc_temp_sensor_init(indio_dev);
-	if (ret)
-		goto per_clk_disable_unprepare;
+	at91_adc_temp_sensor_init(st, &pdev->dev);
 
 	at91_adc_hw_init(indio_dev);