iio: adc: rockchip_saradc: Add support iio buffers

Add the ability to also support access via (triggered) buffers
next to the existing direct mode.

Device in question is the Odroid Go Advance that connects a joystick
to two of the saradc channels for X and Y axis and the new (and still
pending) adc joystick driver of course wants to use triggered buffers
from the iio subsystem.
Signed-off-by: Simon Xue <xxm@rock-chips.com>
[some simplifications and added commit description]
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/rockchip_saradc.c

@@ -15,7 +15,10 @@
 #include <linux/delay.h>
 #include <linux/reset.h>
 #include <linux/regulator/consumer.h>
+#include <linux/iio/buffer.h>
 #include <linux/iio/iio.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
 
 #define SARADC_DATA			0x00
 
@@ -32,9 +35,9 @@
 #define SARADC_DLY_PU_SOC_MASK		0x3f
 
 #define SARADC_TIMEOUT			msecs_to_jiffies(100)
+#define SARADC_MAX_CHANNELS		6
 
 struct rockchip_saradc_data {
-	int				num_bits;
 	const struct iio_chan_spec	*channels;
 	int				num_channels;
 	unsigned long			clk_rate;
@@ -49,8 +52,37 @@ struct rockchip_saradc {
 	struct reset_control	*reset;
 	const struct rockchip_saradc_data *data;
 	u16			last_val;
+	const struct iio_chan_spec *last_chan;
 };
 
+static void rockchip_saradc_power_down(struct rockchip_saradc *info)
+{
+	/* Clear irq & power down adc */
+	writel_relaxed(0, info->regs + SARADC_CTRL);
+}
+
+static int rockchip_saradc_conversion(struct rockchip_saradc *info,
+				   struct iio_chan_spec const *chan)
+{
+	reinit_completion(&info->completion);
+
+	/* 8 clock periods as delay between power up and start cmd */
+	writel_relaxed(8, info->regs + SARADC_DLY_PU_SOC);
+
+	info->last_chan = chan;
+
+	/* Select the channel to be used and trigger conversion */
+	writel(SARADC_CTRL_POWER_CTRL
+			| (chan->channel & SARADC_CTRL_CHN_MASK)
+			| SARADC_CTRL_IRQ_ENABLE,
+		   info->regs + SARADC_CTRL);
+
+	if (!wait_for_completion_timeout(&info->completion, SARADC_TIMEOUT))
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
 static int rockchip_saradc_read_raw(struct iio_dev *indio_dev,
 				    struct iio_chan_spec const *chan,
 				    int *val, int *val2, long mask)
@@ -62,22 +94,11 @@ static int rockchip_saradc_read_raw(struct iio_dev *indio_dev,
 	case IIO_CHAN_INFO_RAW:
 		mutex_lock(&indio_dev->mlock);
 
-		reinit_completion(&info->completion);
-
-		/* 8 clock periods as delay between power up and start cmd */
-		writel_relaxed(8, info->regs + SARADC_DLY_PU_SOC);
-
-		/* Select the channel to be used and trigger conversion */
-		writel(SARADC_CTRL_POWER_CTRL
-				| (chan->channel & SARADC_CTRL_CHN_MASK)
-				| SARADC_CTRL_IRQ_ENABLE,
-		       info->regs + SARADC_CTRL);
-
-		if (!wait_for_completion_timeout(&info->completion,
-						 SARADC_TIMEOUT)) {
-			writel_relaxed(0, info->regs + SARADC_CTRL);
+		ret = rockchip_saradc_conversion(info, chan);
+		if (ret) {
+			rockchip_saradc_power_down(info);
 			mutex_unlock(&indio_dev->mlock);
-			return -ETIMEDOUT;
+			return ret;
 		}
 
 		*val = info->last_val;
@@ -91,7 +112,7 @@ static int rockchip_saradc_read_raw(struct iio_dev *indio_dev,
 		}
 
 		*val = ret / 1000;
-		*val2 = info->data->num_bits;
+		*val2 = chan->scan_type.realbits;
 		return IIO_VAL_FRACTIONAL_LOG2;
 	default:
 		return -EINVAL;
@@ -104,10 +125,9 @@ static irqreturn_t rockchip_saradc_isr(int irq, void *dev_id)
 
 	/* Read value */
 	info->last_val = readl_relaxed(info->regs + SARADC_DATA);
-	info->last_val &= GENMASK(info->data->num_bits - 1, 0);
+	info->last_val &= GENMASK(info->last_chan->scan_type.realbits - 1, 0);
 
-	/* Clear irq & power down adc */
-	writel_relaxed(0, info->regs + SARADC_CTRL);
+	rockchip_saradc_power_down(info);
 
 	complete(&info->completion);
 
@@ -118,51 +138,55 @@ static const struct iio_info rockchip_saradc_iio_info = {
 	.read_raw = rockchip_saradc_read_raw,
 };
 
-#define SARADC_CHANNEL(_index, _id) {				\
+#define SARADC_CHANNEL(_index, _id, _res) {			\
 	.type = IIO_VOLTAGE,					\
 	.indexed = 1,						\
 	.channel = _index,					\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
 	.datasheet_name = _id,					\
+	.scan_index = _index,					\
+	.scan_type = {						\
+		.sign = 'u',					\
+		.realbits = _res,				\
+		.storagebits = 16,				\
+		.endianness = IIO_CPU,				\
+	},							\
 }
 
 static const struct iio_chan_spec rockchip_saradc_iio_channels[] = {
-	SARADC_CHANNEL(0, "adc0"),
-	SARADC_CHANNEL(1, "adc1"),
-	SARADC_CHANNEL(2, "adc2"),
+	SARADC_CHANNEL(0, "adc0", 10),
+	SARADC_CHANNEL(1, "adc1", 10),
+	SARADC_CHANNEL(2, "adc2", 10),
 };
 
 static const struct rockchip_saradc_data saradc_data = {
-	.num_bits = 10,
 	.channels = rockchip_saradc_iio_channels,
 	.num_channels = ARRAY_SIZE(rockchip_saradc_iio_channels),
 	.clk_rate = 1000000,
 };
 
 static const struct iio_chan_spec rockchip_rk3066_tsadc_iio_channels[] = {
-	SARADC_CHANNEL(0, "adc0"),
-	SARADC_CHANNEL(1, "adc1"),
+	SARADC_CHANNEL(0, "adc0", 12),
+	SARADC_CHANNEL(1, "adc1", 12),
 };
 
 static const struct rockchip_saradc_data rk3066_tsadc_data = {
-	.num_bits = 12,
 	.channels = rockchip_rk3066_tsadc_iio_channels,
 	.num_channels = ARRAY_SIZE(rockchip_rk3066_tsadc_iio_channels),
 	.clk_rate = 50000,
 };
 
 static const struct iio_chan_spec rockchip_rk3399_saradc_iio_channels[] = {
-	SARADC_CHANNEL(0, "adc0"),
-	SARADC_CHANNEL(1, "adc1"),
-	SARADC_CHANNEL(2, "adc2"),
-	SARADC_CHANNEL(3, "adc3"),
-	SARADC_CHANNEL(4, "adc4"),
-	SARADC_CHANNEL(5, "adc5"),
+	SARADC_CHANNEL(0, "adc0", 10),
+	SARADC_CHANNEL(1, "adc1", 10),
+	SARADC_CHANNEL(2, "adc2", 10),
+	SARADC_CHANNEL(3, "adc3", 10),
+	SARADC_CHANNEL(4, "adc4", 10),
+	SARADC_CHANNEL(5, "adc5", 10),
 };
 
 static const struct rockchip_saradc_data rk3399_saradc_data = {
-	.num_bits = 10,
 	.channels = rockchip_rk3399_saradc_iio_channels,
 	.num_channels = ARRAY_SIZE(rockchip_rk3399_saradc_iio_channels),
 	.clk_rate = 1000000,
@@ -214,6 +238,46 @@ static void rockchip_saradc_regulator_disable(void *data)
 	regulator_disable(info->vref);
 }
 
+static irqreturn_t rockchip_saradc_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *i_dev = pf->indio_dev;
+	struct rockchip_saradc *info = iio_priv(i_dev);
+	/*
+	 * @values: each channel takes an u16 value
+	 * @timestamp: will be 8-byte aligned automatically
+	 */
+	struct {
+		u16 values[SARADC_MAX_CHANNELS];
+		int64_t timestamp;
+	} data;
+	int ret;
+	int i, j = 0;
+
+	mutex_lock(&i_dev->mlock);
+
+	for_each_set_bit(i, i_dev->active_scan_mask, i_dev->masklength) {
+		const struct iio_chan_spec *chan = &i_dev->channels[i];
+
+		ret = rockchip_saradc_conversion(info, chan);
+		if (ret) {
+			rockchip_saradc_power_down(info);
+			goto out;
+		}
+
+		data.values[j] = info->last_val;
+		j++;
+	}
+
+	iio_push_to_buffers_with_timestamp(i_dev, &data, iio_get_time_ns(i_dev));
+out:
+	mutex_unlock(&i_dev->mlock);
+
+	iio_trigger_notify_done(i_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
 static int rockchip_saradc_probe(struct platform_device *pdev)
 {
 	struct rockchip_saradc *info = NULL;
@@ -242,6 +306,12 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
 
 	info->data = match->data;
 
+	/* Sanity check for possible later IP variants with more channels */
+	if (info->data->num_channels > SARADC_MAX_CHANNELS) {
+		dev_err(&pdev->dev, "max channels exceeded");
+		return -EINVAL;
+	}
+
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	info->regs = devm_ioremap_resource(&pdev->dev, mem);
 	if (IS_ERR(info->regs))
@@ -354,6 +424,11 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
 
 	indio_dev->channels = info->data->channels;
 	indio_dev->num_channels = info->data->num_channels;
+	ret = devm_iio_triggered_buffer_setup(&indio_dev->dev, indio_dev, NULL,
+					      rockchip_saradc_trigger_handler,
+					      NULL);
+	if (ret)
+		return ret;
 
 	return devm_iio_device_register(&pdev->dev, indio_dev);
 }