[PATCH 12/24] staging:iio:cdc:ad7150: Rework interrupt handling.

[Jonathan Cameron <jic23@kernel.org>]

From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Note this doesn't support everything the chip can do as we ignore
window mode for now (in window / out of window).

* Given the chip doesn't have any way of disabling the threshold
  pins, use disable_irq() etc to mask them except when we actually
  want them enabled (previously events were always enabled).
  Note there are race conditions, but using the current state from
  the status register and disabling interrupts across changes in
  type of event should mean those races result in interrupts,
  but no events to userspace.

* Correctly reflect that there is one threshold line per channel.

* Only take notice of rising edge. If anyone wants the other edge
  then they should set the other threshold (they are available for
  rising and falling directions).  This isn't perfect but it makes
  it a lot simpler.

* If insufficient interrupts are specified in firnware, don't support
  events.

* Adaptive events use the same pos/neg values of thrMD as non adaptive
  ones.

Tested against qemu based emulation.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/staging/iio/cdc/ad7150.c | 258 ++++++++++++++++++-------------
 1 file changed, 153 insertions(+), 105 deletions(-)

diff --git a/drivers/staging/iio/cdc/ad7150.c b/drivers/staging/iio/cdc/ad7150.c
index f8183c540d5c..24be97456c03 100644
--- a/drivers/staging/iio/cdc/ad7150.c
+++ b/drivers/staging/iio/cdc/ad7150.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
+#include <linux/irq.h>
 #include <linux/module.h>
 
 #include <linux/iio/iio.h>
@@ -60,8 +61,6 @@ enum {
 /**
  * struct ad7150_chip_info - instance specific chip data
  * @client: i2c client for this device
- * @current_event: device always has one type of event enabled.
- *	This element stores the event code of the current one.
  * @threshold: thresholds for simple capacitance value events
  * @thresh_sensitivity: threshold for simple capacitance offset
  *	from 'average' value.
@@ -70,21 +69,23 @@ enum {
  *	value jumps to current value.  Note made up of two fields,
  *      3:0 are for timeout receding - applies if below lower threshold
  *      7:4 are for timeout approaching - applies if above upper threshold
- * @old_state: store state from previous event, allowing confirmation
- *	of new condition.
- * @conversion_mode: the current conversion mode.
  * @state_lock: ensure consistent state of this structure wrt the
  *	hardware.
+ * @interrupts: one or two interrupt numbers depending on device type.
+ * @int_enabled: is a given interrupt currently enabled.
+ * @type: threshold type
+ * @dir: threshold direction
  */
 struct ad7150_chip_info {
 	struct i2c_client *client;
-	u64 current_event;
 	u16 threshold[2][2];
 	u8 thresh_sensitivity[2][2];
 	u8 thresh_timeout[2][2];
-	int old_state;
-	char *conversion_mode;
 	struct mutex state_lock;
+	int interrupts[2];
+	bool int_enabled[2];
+	enum iio_event_type type;
+	enum iio_event_direction dir;
 };
 
 /*
@@ -158,8 +159,8 @@ static int ad7150_read_event_config(struct iio_dev *indio_dev,
 	switch (type) {
 	case IIO_EV_TYPE_THRESH_ADAPTIVE:
 		if (dir == IIO_EV_DIR_RISING)
-			return !thrfixed && (threshtype == 0x3);
-		return !thrfixed && (threshtype == 0x2);
+			return !thrfixed && (threshtype == 0x1);
+		return !thrfixed && (threshtype == 0x0);
 	case IIO_EV_TYPE_THRESH:
 		if (dir == IIO_EV_DIR_RISING)
 			return thrfixed && (threshtype == 0x1);
@@ -179,11 +180,9 @@ static int ad7150_write_event_params(struct iio_dev *indio_dev,
 {
 	struct ad7150_chip_info *chip = iio_priv(indio_dev);
 	int rising = (dir == IIO_EV_DIR_RISING);
-	u64 event_code;
 
-	event_code = IIO_UNMOD_EVENT_CODE(IIO_CAPACITANCE, chan, type, dir);
-
-	if (event_code != chip->current_event)
+	/* Only update value live, if parameter is in use */
+	if ((type != chip->type) || (dir != chip->dir))
 		return 0;
 
 	switch (type) {
@@ -231,52 +230,91 @@ static int ad7150_write_event_config(struct iio_dev *indio_dev,
 	int ret;
 	struct ad7150_chip_info *chip = iio_priv(indio_dev);
 	int rising = (dir == IIO_EV_DIR_RISING);
-	u64 event_code;
-
-	/* Something must always be turned on */
-	if (!state)
-		return -EINVAL;
 
-	event_code = IIO_UNMOD_EVENT_CODE(chan->type, chan->channel, type, dir);
-	if (event_code == chip->current_event)
+	/*
+	 * There is only a single shared control and no on chip
+	 * interrupt disables for the two interrupt lines.
+	 * So, enabling will switch the events configured to enable
+	 * whatever was most recently requested and if necessary enable_irq()
+	 * the interrupt and any disable will disable_irq() for that
+	 * channels interrupt.
+	 */
+	if (!state) {
+		if ((chip->int_enabled[chan->channel]) &&
+		    (type == chip->type) && (dir == chip->dir)) {
+			disable_irq(chip->interrupts[chan->channel]);
+			chip->int_enabled[chan->channel] = false;
+		}
 		return 0;
+	}
+
 	mutex_lock(&chip->state_lock);
-	ret = i2c_smbus_read_byte_data(chip->client, AD7150_CFG);
-	if (ret < 0)
-		goto error_ret;
+	if ((type != chip->type) || (dir != chip->dir)) {
 
-	cfg = ret & ~((0x03 << 5) | BIT(7));
+		/*
+		 * Need to temporarily disable both interrupts if
+		 * enabled - this is to avoid races around changing
+		 * config and thresholds.
+		 * Note enable/disable_irq() are reference counted so
+		 * no need to check if already enabled.
+		 */
+		disable_irq(chip->interrupts[0]);
+		disable_irq(chip->interrupts[1]);
 
-	switch (type) {
-	case IIO_EV_TYPE_THRESH_ADAPTIVE:
-		adaptive = 1;
-		if (rising)
-			thresh_type = 0x3;
-		else
-			thresh_type = 0x2;
-		break;
-	case IIO_EV_TYPE_THRESH:
-		adaptive = 0;
-		if (rising)
-			thresh_type = 0x1;
-		else
-			thresh_type = 0x0;
-		break;
-	default:
-		ret = -EINVAL;
-		goto error_ret;
-	}
+		ret = i2c_smbus_read_byte_data(chip->client, AD7150_CFG);
+		if (ret < 0)
+			goto error_ret;
 
-	cfg |= (!adaptive << 7) | (thresh_type << 5);
+		cfg = ret & ~((0x03 << 5) | BIT(7));
 
-	ret = i2c_smbus_write_byte_data(chip->client, AD7150_CFG, cfg);
-	if (ret < 0)
-		goto error_ret;
+		switch (type) {
+		case IIO_EV_TYPE_THRESH_ADAPTIVE:
+			adaptive = 1;
+			if (rising)
+				thresh_type = 0x1;
+			else
+				thresh_type = 0x0;
+			break;
+		case IIO_EV_TYPE_THRESH:
+			adaptive = 0;
+			if (rising)
+				thresh_type = 0x1;
+			else
+				thresh_type = 0x0;
+			break;
+		default:
+			ret = -EINVAL;
+			goto error_ret;
+		}
 
-	chip->current_event = event_code;
+		cfg |= (!adaptive << 7) | (thresh_type << 5);
+
+		ret = i2c_smbus_write_byte_data(chip->client, AD7150_CFG, cfg);
+		if (ret < 0)
+			goto error_ret;
+
+		/*
+		 * There is a potential race condition here, but not easy
+		 * to close given we can't disable the interrupt at the
+		 * chip side of things. Rely on the status bit.
+		 */
+		chip->type = type;
+		chip->dir = dir;
+
+		/* update control attributes */
+		ret = ad7150_write_event_params(indio_dev, chan->channel, type,
+						dir);
+		if (ret)
+			goto error_ret;
+		/* reenable any irq's we disabled whilst changing mode */
+		enable_irq(chip->interrupts[0]);
+		enable_irq(chip->interrupts[1]);
+	}
+	if (!chip->int_enabled[chan->channel]) {
+		enable_irq(chip->interrupts[chan->channel]);
+		chip->int_enabled[chan->channel] = true;
+	}
 
-	/* update control attributes */
-	ret = ad7150_write_event_params(indio_dev, chan->channel, type, dir);
 error_ret:
 	mutex_unlock(&chip->state_lock);
 
@@ -434,59 +472,44 @@ static const struct iio_chan_spec ad7151_channels_no_irq[] = {
 	AD7150_CAPACITANCE_CHAN_NO_IRQ(0),
 };
 
-static irqreturn_t ad7150_event_handler(int irq, void *private)
+static irqreturn_t __ad7150_event_handler(void *private, u8 status_mask,
+					  int channel)
 {
 	struct iio_dev *indio_dev = private;
 	struct ad7150_chip_info *chip = iio_priv(indio_dev);
-	u8 int_status;
 	s64 timestamp = iio_get_time_ns(indio_dev);
-	int ret;
+	int int_status;
 
-	ret = i2c_smbus_read_byte_data(chip->client, AD7150_STATUS);
-	if (ret < 0)
+	int_status = i2c_smbus_read_byte_data(chip->client, AD7150_STATUS);
+	if (int_status < 0)
 		return IRQ_HANDLED;
 
-	int_status = ret;
-
-	if ((int_status & AD7150_STATUS_OUT1) &&
-	    !(chip->old_state & AD7150_STATUS_OUT1))
-		iio_push_event(indio_dev,
-			       IIO_UNMOD_EVENT_CODE(IIO_CAPACITANCE,
-						    0,
-						    IIO_EV_TYPE_THRESH,
-						    IIO_EV_DIR_RISING),
-				timestamp);
-	else if ((!(int_status & AD7150_STATUS_OUT1)) &&
-		 (chip->old_state & AD7150_STATUS_OUT1))
-		iio_push_event(indio_dev,
-			       IIO_UNMOD_EVENT_CODE(IIO_CAPACITANCE,
-						    0,
-						    IIO_EV_TYPE_THRESH,
-						    IIO_EV_DIR_FALLING),
-			       timestamp);
-
-	if ((int_status & AD7150_STATUS_OUT2) &&
-	    !(chip->old_state & AD7150_STATUS_OUT2))
-		iio_push_event(indio_dev,
-			       IIO_UNMOD_EVENT_CODE(IIO_CAPACITANCE,
-						    1,
-						    IIO_EV_TYPE_THRESH,
-						    IIO_EV_DIR_RISING),
-			       timestamp);
-	else if ((!(int_status & AD7150_STATUS_OUT2)) &&
-		 (chip->old_state & AD7150_STATUS_OUT2))
-		iio_push_event(indio_dev,
-			       IIO_UNMOD_EVENT_CODE(IIO_CAPACITANCE,
-						    1,
-						    IIO_EV_TYPE_THRESH,
-						    IIO_EV_DIR_FALLING),
-			       timestamp);
-	/* store the status to avoid repushing same events */
-	chip->old_state = int_status;
+	/*
+	 * There are race conditions around enabling and disabling that
+	 * could easily land us here with a spurious interrupt.
+	 * Just eat it if so.
+	 */
+	if (!(int_status & status_mask))
+		return IRQ_HANDLED;
+
+	iio_push_event(indio_dev,
+		       IIO_UNMOD_EVENT_CODE(IIO_CAPACITANCE, channel,
+					    chip->type, chip->dir),
+		       timestamp);
 
 	return IRQ_HANDLED;
 }
 
+static irqreturn_t ad7150_event_handler_ch1(int irq, void *private)
+{
+	return __ad7150_event_handler(private, AD7150_STATUS_OUT1, 0);
+}
+
+static irqreturn_t ad7150_event_handler_ch2(int irq, void *private)
+{
+	return __ad7150_event_handler(private, AD7150_STATUS_OUT2, 1);
+}
+
 static IIO_CONST_ATTR(in_capacitance_thresh_adaptive_timeout_available,
 		      "[0 0.01 0.15]");
 
@@ -533,12 +556,44 @@ static int ad7150_probe(struct i2c_client *client,
 
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
-	if (client->irq) {
+	chip->interrupts[0] = fwnode_irq_get(dev_fwnode(&client->dev), 0);
+	if (chip->interrupts[0] < 0)
+		return chip->interrupts[0];
+	if (id->driver_data == AD7150) {
+		chip->interrupts[1] = fwnode_irq_get(dev_fwnode(&client->dev), 1);
+		if (chip->interrupts[1] < 0)
+			return chip->interrupts[1];
+	}
+	if (chip->interrupts[0] &&
+	    (id->driver_data == AD7151 || chip->interrupts[1])) {
+		irq_set_status_flags(chip->interrupts[0], IRQ_NOAUTOEN);
+		ret = devm_request_threaded_irq(&client->dev,
+						chip->interrupts[0],
+						NULL,
+						&ad7150_event_handler_ch1,
+						IRQF_TRIGGER_RISING |
+						IRQF_ONESHOT,
+						"ad7150_irq1",
+						indio_dev);
+		if (ret)
+			return ret;
+
 		indio_dev->info = &ad7150_info;
 		switch (id->driver_data) {
 		case AD7150:
 			indio_dev->channels = ad7150_channels;
 			indio_dev->num_channels = ARRAY_SIZE(ad7150_channels);
+			irq_set_status_flags(chip->interrupts[1], IRQ_NOAUTOEN);
+			ret = devm_request_threaded_irq(&client->dev,
+							chip->interrupts[1],
+							NULL,
+							&ad7150_event_handler_ch2,
+							IRQF_TRIGGER_RISING |
+							IRQF_ONESHOT,
+							"ad7150_irq2",
+							indio_dev);
+			if (ret)
+				return ret;
 			break;
 		case AD7151:
 			indio_dev->channels = ad7151_channels;
@@ -548,25 +603,18 @@ static int ad7150_probe(struct i2c_client *client,
 			return -EINVAL;
 		}
 
-		ret = devm_request_threaded_irq(&client->dev, client->irq,
-						NULL,
-						&ad7150_event_handler,
-						IRQF_TRIGGER_RISING |
-						IRQF_ONESHOT,
-						"ad7150_irq1",
-						indio_dev);
-		if (ret)
-			return ret;
 	} else {
 		indio_dev->info = &ad7150_info_no_irq;
 		switch (id->driver_data) {
 		case AD7150:
 			indio_dev->channels = ad7150_channels_no_irq;
-			indio_dev->num_channels = ARRAY_SIZE(ad7150_channels_no_irq);
+			indio_dev->num_channels =
+				ARRAY_SIZE(ad7150_channels_no_irq);
 			break;
 		case AD7151:
 			indio_dev->channels = ad7151_channels_no_irq;
-			indio_dev->num_channels = ARRAY_SIZE(ad7151_channels_no_irq);
+			indio_dev->num_channels =
+				ARRAY_SIZE(ad7151_channels_no_irq);
 			break;
 		default:
 			return -EINVAL;
-- 
2.30.0