iio: mxs-lradc: add write_raw function to modify scale

Added write_raw function to manipulate the optional divider_by_two
through the scaling attribute out of the available scales.
Signed-off-by: Hector Palacios <hector.palacios@digi.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/mxs-lradc.c

@@ -185,6 +185,11 @@ enum lradc_ts_plate {
 	LRADC_SAMPLE_VALID,
 };
 
+enum mxs_lradc_divbytwo {
+	MXS_LRADC_DIV_DISABLED = 0,
+	MXS_LRADC_DIV_ENABLED,
+};
+
 struct mxs_lradc_scale {
 	unsigned int		integer;
 	unsigned int		nano;
@@ -206,6 +211,7 @@ struct mxs_lradc {
 
 	const uint32_t		*vref_mv;
 	struct mxs_lradc_scale	scale_avail[LRADC_MAX_TOTAL_CHANS][2];
+	unsigned int		is_divided[LRADC_MAX_TOTAL_CHANS];
 
 	/*
 	 * Touchscreen LRADC channels receives a private slot in the CTRL4
@@ -295,6 +301,7 @@ struct mxs_lradc {
 #define	LRADC_CTRL1_LRADC_IRQ_OFFSET		0
 
 #define	LRADC_CTRL2				0x20
+#define	LRADC_CTRL2_DIVIDE_BY_TWO_OFFSET	24
 #define	LRADC_CTRL2_TEMPSENSE_PWD		(1 << 15)
 
 #define	LRADC_STATUS				0x40
@@ -912,7 +919,8 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
 		}
 
 		*val = lradc->vref_mv[chan->channel];
-		*val2 = chan->scan_type.realbits;
+		*val2 = chan->scan_type.realbits -
+			lradc->is_divided[chan->channel];
 		return IIO_VAL_FRACTIONAL_LOG2;
 
 	case IIO_CHAN_INFO_OFFSET:
@@ -936,6 +944,56 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
 	return -EINVAL;
 }
 
+static int mxs_lradc_write_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);
+	struct mxs_lradc_scale *scale_avail =
+			lradc->scale_avail[chan->channel];
+	int ret;
+
+	ret = mutex_trylock(&lradc->lock);
+	if (!ret)
+		return -EBUSY;
+
+	switch (m) {
+	case IIO_CHAN_INFO_SCALE:
+		ret = -EINVAL;
+		if (val == scale_avail[MXS_LRADC_DIV_DISABLED].integer &&
+		    val2 == scale_avail[MXS_LRADC_DIV_DISABLED].nano) {
+			/* divider by two disabled */
+			writel(1 << LRADC_CTRL2_DIVIDE_BY_TWO_OFFSET,
+			       lradc->base + LRADC_CTRL2 + STMP_OFFSET_REG_CLR);
+			lradc->is_divided[chan->channel] = 0;
+			ret = 0;
+		} else if (val == scale_avail[MXS_LRADC_DIV_ENABLED].integer &&
+			   val2 == scale_avail[MXS_LRADC_DIV_ENABLED].nano) {
+			/* divider by two enabled */
+			writel(1 << LRADC_CTRL2_DIVIDE_BY_TWO_OFFSET,
+			       lradc->base + LRADC_CTRL2 + STMP_OFFSET_REG_SET);
+			lradc->is_divided[chan->channel] = 1;
+			ret = 0;
+		}
+
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	mutex_unlock(&lradc->lock);
+
+	return ret;
+}
+
+static int mxs_lradc_write_raw_get_fmt(struct iio_dev *iio_dev,
+				       const struct iio_chan_spec *chan,
+				       long m)
+{
+	return IIO_VAL_INT_PLUS_NANO;
+}
+
 static ssize_t mxs_lradc_show_scale_available_ch(struct device *dev,
 		struct device_attribute *attr,
 		char *buf,
@@ -1013,6 +1071,8 @@ static const struct attribute_group mxs_lradc_attribute_group = {
 static const struct iio_info mxs_lradc_iio_info = {
 	.driver_module		= THIS_MODULE,
 	.read_raw		= mxs_lradc_read_raw,
+	.write_raw		= mxs_lradc_write_raw,
+	.write_raw_get_fmt	= mxs_lradc_write_raw_get_fmt,
 	.attrs			= &mxs_lradc_attribute_group,
 };