iio: mxs-lradc: add scale_available file to channels

Adds in_voltageX_scale_available file for every channel to read
the different available scales.
There are two scales per channel:
 [0] = divider_by_two disabled (default)
 [1] = divider_by_two enabled
The scale is a struct made of integer and nano parts to build
a long decimal number.
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

@@ -38,6 +38,7 @@
 #include <linux/clk.h>
 
 #include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
 #include <linux/iio/buffer.h>
 #include <linux/iio/trigger.h>
 #include <linux/iio/trigger_consumer.h>
@@ -184,6 +185,11 @@ enum lradc_ts_plate {
 	LRADC_SAMPLE_VALID,
 };
 
+struct mxs_lradc_scale {
+	unsigned int		integer;
+	unsigned int		nano;
+};
+
 struct mxs_lradc {
 	struct device		*dev;
 	void __iomem		*base;
@@ -199,6 +205,7 @@ struct mxs_lradc {
 	struct completion	completion;
 
 	const uint32_t		*vref_mv;
+	struct mxs_lradc_scale	scale_avail[LRADC_MAX_TOTAL_CHANS][2];
 
 	/*
 	 * Touchscreen LRADC channels receives a private slot in the CTRL4
@@ -929,9 +936,84 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
 	return -EINVAL;
 }
 
+static ssize_t mxs_lradc_show_scale_available_ch(struct device *dev,
+		struct device_attribute *attr,
+		char *buf,
+		int ch)
+{
+	struct iio_dev *iio = dev_to_iio_dev(dev);
+	struct mxs_lradc *lradc = iio_priv(iio);
+	int i, len = 0;
+
+	for (i = 0; i < ARRAY_SIZE(lradc->scale_avail[ch]); i++)
+		len += sprintf(buf + len, "%d.%09u ",
+			       lradc->scale_avail[ch][i].integer,
+			       lradc->scale_avail[ch][i].nano);
+
+	len += sprintf(buf + len, "\n");
+
+	return len;
+}
+
+static ssize_t mxs_lradc_show_scale_available(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	struct iio_dev_attr *iio_attr = to_iio_dev_attr(attr);
+
+	return mxs_lradc_show_scale_available_ch(dev, attr, buf,
+						 iio_attr->address);
+}
+
+#define SHOW_SCALE_AVAILABLE_ATTR(ch)					\
+static IIO_DEVICE_ATTR(in_voltage##ch##_scale_available, S_IRUGO,	\
+		       mxs_lradc_show_scale_available, NULL, ch)
+
+SHOW_SCALE_AVAILABLE_ATTR(0);
+SHOW_SCALE_AVAILABLE_ATTR(1);
+SHOW_SCALE_AVAILABLE_ATTR(2);
+SHOW_SCALE_AVAILABLE_ATTR(3);
+SHOW_SCALE_AVAILABLE_ATTR(4);
+SHOW_SCALE_AVAILABLE_ATTR(5);
+SHOW_SCALE_AVAILABLE_ATTR(6);
+SHOW_SCALE_AVAILABLE_ATTR(7);
+SHOW_SCALE_AVAILABLE_ATTR(8);
+SHOW_SCALE_AVAILABLE_ATTR(9);
+SHOW_SCALE_AVAILABLE_ATTR(10);
+SHOW_SCALE_AVAILABLE_ATTR(11);
+SHOW_SCALE_AVAILABLE_ATTR(12);
+SHOW_SCALE_AVAILABLE_ATTR(13);
+SHOW_SCALE_AVAILABLE_ATTR(14);
+SHOW_SCALE_AVAILABLE_ATTR(15);
+
+static struct attribute *mxs_lradc_attributes[] = {
+	&iio_dev_attr_in_voltage0_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage1_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage2_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage3_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage4_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage5_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage6_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage7_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage8_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage9_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage10_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage11_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage12_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage13_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage14_scale_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage15_scale_available.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group mxs_lradc_attribute_group = {
+	.attrs = mxs_lradc_attributes,
+};
+
 static const struct iio_info mxs_lradc_iio_info = {
 	.driver_module		= THIS_MODULE,
 	.read_raw		= mxs_lradc_read_raw,
+	.attrs			= &mxs_lradc_attribute_group,
 };
 
 static int mxs_lradc_ts_open(struct input_dev *dev)
@@ -1241,6 +1323,7 @@ static const struct iio_buffer_setup_ops mxs_lradc_buffer_ops = {
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |		\
 			      BIT(IIO_CHAN_INFO_SCALE),		\
 	.channel = (idx),					\
+	.address = (idx),					\
 	.scan_type = {						\
 		.sign = 'u',					\
 		.realbits = LRADC_RESOLUTION,			\
@@ -1386,7 +1469,8 @@ static int mxs_lradc_probe(struct platform_device *pdev)
 	struct iio_dev *iio;
 	struct resource *iores;
 	int ret = 0, touch_ret;
-	int i;
+	int i, s;
+	unsigned int scale_uv;
 
 	/* Allocate the IIO device. */
 	iio = devm_iio_device_alloc(dev, sizeof(*lradc));
@@ -1456,6 +1540,26 @@ static int mxs_lradc_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_trig;
 
+	/* Populate available ADC input ranges */
+	for (i = 0; i < LRADC_MAX_TOTAL_CHANS; i++) {
+		for (s = 0; s < ARRAY_SIZE(lradc->scale_avail[i]); s++) {
+			/*
+			 * [s=0] = optional divider by two disabled (default)
+			 * [s=1] = optional divider by two enabled
+			 *
+			 * The scale is calculated by doing:
+			 *   Vref >> (realbits - s)
+			 * which multiplies by two on the second component
+			 * of the array.
+			 */
+			scale_uv = ((u64)lradc->vref_mv[i] * 100000000) >>
+				   (iio->channels[i].scan_type.realbits - s);
+			lradc->scale_avail[i][s].nano =
+					do_div(scale_uv, 100000000) * 10;
+			lradc->scale_avail[i][s].integer = scale_uv;
+		}
+	}
+
 	/* Configure the hardware. */
 	ret = mxs_lradc_hw_init(lradc);
 	if (ret)