iio: ti_am335x_adc: Allow to specify input line

The TSC part allows to specify the input lines. The IIO part assumes
that it usues always the last few, that means if IIO has adc-channels
set to 2 it will use channel 6 and 7. However it might make sense to use
only 6.
This patch changes the device property (which was introduced recently
and was never in an official release) in a way that the user can specify
which of the AIN lines should be used. In Addition to this, the name is
now AINx where x is the channel number i.e. for AIN6 we would have 6.
Prior this, it always started counting at 0 which is confusing. In
addition to this, it also checks for correct step number during reading
and does not rely on proper FIFO depth.

Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

arch/arm/boot/dts/am335x-evm.dts

@@ -255,6 +255,6 @@
 	};
 
 	adc {
-		ti,adc-channels = <4>;
+		ti,adc-channels = <4 5 6 7>;
 	};
 };

drivers/iio/adc/ti_am335x_adc.c

@@ -32,6 +32,8 @@
 struct tiadc_device {
 	struct ti_tscadc_dev *mfd_tscadc;
 	int channels;
+	u8 channel_line[8];
+	u8 channel_step[8];
 };
 
 static unsigned int tiadc_readl(struct tiadc_device *adc, unsigned int reg)
@@ -57,7 +59,7 @@ static u32 get_adc_step_mask(struct tiadc_device *adc_dev)
 static void tiadc_step_config(struct tiadc_device *adc_dev)
 {
 	unsigned int stepconfig;
-	int i, channels = 0, steps;
+	int i, steps;
 	u32 step_en;
 
 	/*
@@ -71,16 +73,18 @@ static void tiadc_step_config(struct tiadc_device *adc_dev)
 	 */
 
 	steps = TOTAL_STEPS - adc_dev->channels;
-	channels = TOTAL_CHANNELS - adc_dev->channels;
-
 	stepconfig = STEPCONFIG_AVG_16 | STEPCONFIG_FIFO1;
 
-	for (i = steps; i < TOTAL_STEPS; i++) {
-		tiadc_writel(adc_dev, REG_STEPCONFIG(i),
-				stepconfig | STEPCONFIG_INP(channels));
-		tiadc_writel(adc_dev, REG_STEPDELAY(i),
+	for (i = 0; i < adc_dev->channels; i++) {
+		int chan;
+
+		chan = adc_dev->channel_line[i];
+		tiadc_writel(adc_dev, REG_STEPCONFIG(steps),
+				stepconfig | STEPCONFIG_INP(chan));
+		tiadc_writel(adc_dev, REG_STEPDELAY(steps),
 				STEPCONFIG_OPENDLY);
-		channels++;
+		adc_dev->channel_step[i] = steps;
+		steps++;
 	}
 	step_en = get_adc_step_mask(adc_dev);
 	am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
@@ -115,9 +119,9 @@ static int tiadc_channel_init(struct iio_dev *indio_dev, int channels)
 
 		chan->type = IIO_VOLTAGE;
 		chan->indexed = 1;
-		chan->channel = i;
+		chan->channel = adc_dev->channel_line[i];
 		chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
-		chan->datasheet_name = chan_name_ain[i];
+		chan->datasheet_name = chan_name_ain[chan->channel];
 		chan->scan_type.sign = 'u';
 		chan->scan_type.realbits = 12;
 		chan->scan_type.storagebits = 32;
@@ -139,7 +143,8 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
 {
 	struct tiadc_device *adc_dev = iio_priv(indio_dev);
 	int i;
-	unsigned int fifo1count, readx1;
+	unsigned int fifo1count, read;
+	u32 step = UINT_MAX;
 
 	/*
 	 * When the sub-system is first enabled,
@@ -152,11 +157,20 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
 	 * Hence we need to flush out this data.
 	 */
 
+	for (i = 0; i < ARRAY_SIZE(adc_dev->channel_step); i++) {
+		if (chan->channel == adc_dev->channel_line[i]) {
+			step = adc_dev->channel_step[i];
+			break;
+		}
+	}
+	if (WARN_ON_ONCE(step == UINT_MAX))
+		return -EINVAL;
+
 	fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
 	for (i = 0; i < fifo1count; i++) {
-		readx1 = tiadc_readl(adc_dev, REG_FIFO1);
-		if (i == chan->channel)
-			*val = readx1 & 0xfff;
+		read = tiadc_readl(adc_dev, REG_FIFO1);
+		if (read >> 16 == step)
+			*val = read & 0xfff;
 	}
 	am335x_tsc_se_update(adc_dev->mfd_tscadc);
 
@@ -172,8 +186,11 @@ static int tiadc_probe(struct platform_device *pdev)
 	struct iio_dev		*indio_dev;
 	struct tiadc_device	*adc_dev;
 	struct device_node	*node = pdev->dev.of_node;
+	struct property		*prop;
+	const __be32		*cur;
 	int			err;
-	u32			val32;
+	u32			val;
+	int			channels = 0;
 
 	if (!node) {
 		dev_err(&pdev->dev, "Could not find valid DT data.\n");
@@ -190,11 +207,11 @@ static int tiadc_probe(struct platform_device *pdev)
 
 	adc_dev->mfd_tscadc = ti_tscadc_dev_get(pdev);
 
-	err = of_property_read_u32(node,
-			"ti,adc-channels", &val32);
-	if (err < 0)
-		goto err_free_device;
-	adc_dev->channels = val32;
+	of_property_for_each_u32(node, "ti,adc-channels", prop, cur, val) {
+		adc_dev->channel_line[channels] = val;
+		channels++;
+	}
+	adc_dev->channels = channels;
 
 	indio_dev->dev.parent = &pdev->dev;
 	indio_dev->name = dev_name(&pdev->dev);

drivers/mfd/ti_am335x_tscadc.c

@@ -91,9 +91,13 @@ static	int ti_tscadc_probe(struct platform_device *pdev)
 	struct clk		*clk;
 	struct device_node	*node = pdev->dev.of_node;
 	struct mfd_cell		*cell;
+	struct property         *prop;
+	const __be32            *cur;
+	u32			val;
 	int			err, ctrl;
 	int			clk_value, clock_rate;
 	int			tsc_wires = 0, adc_channels = 0, total_channels;
+	int			readouts = 0;
 
 	if (!pdev->dev.of_node) {
 		dev_err(&pdev->dev, "Could not find valid DT data.\n");
@@ -102,10 +106,17 @@ static	int ti_tscadc_probe(struct platform_device *pdev)
 
 	node = of_get_child_by_name(pdev->dev.of_node, "tsc");
 	of_property_read_u32(node, "ti,wires", &tsc_wires);
+	of_property_read_u32(node, "ti,coordiante-readouts", &readouts);
 
 	node = of_get_child_by_name(pdev->dev.of_node, "adc");
-	of_property_read_u32(node, "ti,adc-channels", &adc_channels);
-
+	of_property_for_each_u32(node, "ti,adc-channels", prop, cur, val) {
+		adc_channels++;
+		if (val > 7) {
+			dev_err(&pdev->dev, " PIN numbers are 0..7 (not %d)\n",
+					val);
+			return -EINVAL;
+		}
+	}
 	total_channels = tsc_wires + adc_channels;
 	if (total_channels > 8) {
 		dev_err(&pdev->dev, "Number of i/p channels more than 8\n");
@@ -116,6 +127,11 @@ static	int ti_tscadc_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
+	if (readouts * 2 + 2 + adc_channels > 16) {
+		dev_err(&pdev->dev, "Too many step configurations requested\n");
+		return -EINVAL;
+	}
+
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!res) {
 		dev_err(&pdev->dev, "no memory resource defined.\n");