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 <[e-mail]>
Signed-off-by: Sebastian Andrzej Siewior <[e-mail]>

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

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

drivers/iio/adc/ti_am335x_adc.c

···
 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)
···
 static void tiadc_step_config(struct tiadc_device *adc_dev)
 {
 	unsigned int stepconfig;
-	int i, channels = 0, steps;
+	int i, steps;
 	u32 step_en;
 
 	/*
···
 	 */
 
 	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);
···
 
 		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;
···
 {
 	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,
···
 	 * 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);
 
···
 	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");
···
 
 	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

···
 	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");
···
 
 	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");
···
 	}
 	if (total_channels == 0) {
 		dev_err(&pdev->dev, "Need atleast one channel.\n");
+		return -EINVAL;
+	}
+
+	if (readouts * 2 + 2 + adc_channels > 16) {
+		dev_err(&pdev->dev, "Too many step configurations requested\n");
 		return -EINVAL;
 	}