[PATCH v2 3/5] iio: mxs-lradc: add scale attribute to channels

[Hector Palacios <hector.palacios@digi.com>]

Some LRADC channels have fixed pre-dividers and all have an optional
divider by two which allows a maximum input voltage of VDDIO - 50mV.

This patch
 - adds the scaling info flag to all channels
 - grabs the max reference voltage per channel from DT
   (where the fixed pre-dividers apply)
 - allows to read the scaling attribute (computed from the Vref)

Signed-off-by: Hector Palacios <hector.palacios@digi.com>.
---
 drivers/staging/iio/adc/mxs-lradc.c | 81 ++++++++++++++++++++++++-------------
 1 file changed, 52 insertions(+), 29 deletions(-)

diff --git a/drivers/staging/iio/adc/mxs-lradc.c b/drivers/staging/iio/adc/mxs-lradc.c
index 91282dc..99e5790 100644
--- a/drivers/staging/iio/adc/mxs-lradc.c
+++ b/drivers/staging/iio/adc/mxs-lradc.c
@@ -141,6 +141,8 @@ struct mxs_lradc {
 
 	struct completion	completion;
 
+	uint32_t		vref_mv[LRADC_MAX_TOTAL_CHANS];
+
 	/*
 	 * Touchscreen LRADC channels receives a private slot in the CTRL4
 	 * register, the slot #7. Therefore only 7 slots instead of 8 in the
@@ -228,39 +230,12 @@ struct mxs_lradc {
 #define LRADC_RESOLUTION			12
 #define LRADC_SINGLE_SAMPLE_MASK		((1 << LRADC_RESOLUTION) - 1)
 
-/*
- * Raw I/O operations
- */
-static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
+static int mxs_lradc_read_single(struct iio_dev *iio_dev,
 			const struct iio_chan_spec *chan,
 			int *val, int *val2, long m)
 {
 	struct mxs_lradc *lradc = iio_priv(iio_dev);
 	int ret;
-	unsigned long mask;
-
-	if (m != IIO_CHAN_INFO_RAW)
-		return -EINVAL;
-
-	/* Check for invalid channel */
-	if (chan->channel > LRADC_MAX_TOTAL_CHANS)
-		return -EINVAL;
-
-	/* Validate the channel if it doesn't intersect with reserved chans. */
-	bitmap_set(&mask, chan->channel, 1);
-	ret = iio_validate_scan_mask_onehot(iio_dev, &mask);
-	if (ret)
-		return -EINVAL;
-
-	/*
-	 * See if there is no buffered operation in progess. If there is, simply
-	 * bail out. This can be improved to support both buffered and raw IO at
-	 * the same time, yet the code becomes horribly complicated. Therefore I
-	 * applied KISS principle here.
-	 */
-	ret = mutex_trylock(&lradc->lock);
-	if (!ret)
-		return -EBUSY;
 
 	INIT_COMPLETION(lradc->completion);
 
@@ -300,6 +275,47 @@ err:
 	writel(LRADC_CTRL1_LRADC_IRQ_EN(0),
 		lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);
 
+	return ret;
+}
+
+/*
+ * Raw I/O operations
+ */
+static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
+			const struct iio_chan_spec *chan,
+			int *val, int *val2, long m)
+{
+	struct mxs_lradc *lradc = iio_priv(iio_dev);
+	int ret;
+
+	/*
+	 * See if there is no buffered operation in progress. If there is, simply
+	 * bail out. This can be improved to support both buffered and raw IO at
+	 * the same time, yet the code becomes horribly complicated. Therefore I
+	 * applied KISS principle here.
+	 */
+	ret = mutex_trylock(&lradc->lock);
+	if (!ret)
+		return -EBUSY;
+
+	/* Check for invalid channel */
+	if (chan->channel > LRADC_MAX_TOTAL_CHANS)
+		ret = -EINVAL;
+
+	switch (m) {
+	case IIO_CHAN_INFO_RAW:
+		ret = mxs_lradc_read_single(iio_dev, chan, val, val2, m);
+		break;
+	case IIO_CHAN_INFO_SCALE:
+		*val = lradc->vref_mv[chan->channel];
+		*val2 = chan->scan_type.realbits;
+		ret = IIO_VAL_FRACTIONAL_LOG2;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
 	mutex_unlock(&lradc->lock);
 
 	return ret;
@@ -821,7 +837,8 @@ static const struct iio_buffer_setup_ops mxs_lradc_buffer_ops = {
 	.type = (chan_type),					\
 	.indexed = 1,						\
 	.scan_index = (idx),					\
-	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |		\
+			      BIT(IIO_CHAN_INFO_SCALE),		\
 	.channel = (idx),					\
 	.scan_type = {						\
 		.sign = 'u',					\
@@ -960,6 +977,12 @@ static int mxs_lradc_probe(struct platform_device *pdev)
 			goto err_addr;
 	}
 
+	/* Grab Vref array from DT */
+	ret = of_property_read_u32_array(node, "fsl,vref", lradc->vref_mv,
+					 LRADC_MAX_TOTAL_CHANS);
+	if (ret)
+		goto err_addr;
+
 	platform_set_drvdata(pdev, iio);
 
 	init_completion(&lradc->completion);