On Sat, 13 Jul 2019 10:04:55 +0200
Alexandre Mergnat [off-list ref] wrote:

This adds support for PixArt Imaging’s miniature low power optical
navigation chip using LASER light source enabling digital surface tracking.

Features and datasheet: [0]

This IIO driver allows to read relative position from where the system
started on X and Y axis through two way:
  - Punctual "read_raw" which will issue a read in the device registers to
  get the delta between last/current read and return the addition of all
  the deltas.
  - Buffer read. Data can be retrieved using triggered buffer subscription
  (i.e. iio_readdev). The buffer payload is:
    |32 bits delta X|32 bits delta Y|timestamp|.

The possible I2C addresses are 0x73, 0x75 and 0x79.

X and Y axis CPI resolution can be get/set independently through IIO_SCALE.
The range value is 0-255 which means:
  - 0 to ~1,275 Counts Per Inch on flat surface.
  - 0 to ~630 Counts Per Rev on 1.0mm diameter STS shaft at 1.0mm distance.
More details on the datasheet.

The "position" directory is added to contain drivers which can provide
position data.

[0]: http://www.pixart.com/products-detail/72/PAT9125EL-TKIT___TKMT

Signed-off-by: Alexandre Mergnat <redacted>

Hi Alexandre,

Sorry for the lack of reply to the previous version. To much jet
lag and travelling recently so I'm just catching up today.

I still want to get the bottom of why the level interrupt
approach isn't working.

I've played these games with using edge interrupts and
try_reenable tricks in the past and they very rarely work out
in the long term.

The issue with try_reenable calling iio_poll_trigger
looks to be a bug in the IIO core, so a patch to fix
that would be welcome!

A few minor other bits inline.

Jonathan

Please use naming that associates these with which register
they are in.

+
+/* Registers' values */
+#define PAT9125_SENSOR_ID_VAL			0x31
+#define PAT9125_DISABLE_WRITE_PROTECT_VAL	0x5A
+#define PAT9125_ENABLE_WRITE_PROTECT_VAL	0x00
+
+/* Default Value of sampled value size */
+#define PAT9125_SAMPLED_VAL_BIT_SIZE		12
+
+struct pat9125_data {
+	struct regmap *regmap;
+	struct iio_trigger *indio_trig;	/* Motion detection */
+	s32 position_x;
+	s32 position_y;
+	bool sampling;
+};
+
+static const struct iio_chan_spec pat9125_channels[] = {
+	{
+		.type = IIO_DISTANCE,
+		.modified = 1,
+		.channel2 = IIO_MOD_X,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 32,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
+	},
+	{
+		.type = IIO_DISTANCE,
+		.modified = 1,
+		.channel2 = IIO_MOD_Y,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 1,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 32,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
+	},
+	IIO_CHAN_SOFT_TIMESTAMP(2),
+};
+
+/**
+ * pat9125_write_pretected_reg() - Write value in protected register.
+ *
+ * @regmap: Pointer to I2C register map.
+ * @reg_addr: Register address.
+ * @reg_value: Value to be write in register.
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+static int pat9125_write_pretected_reg(struct iio_dev *indio_dev,
+	u8 reg_addr, u8 reg_value)
+{
+	struct pat9125_data *data = iio_priv(indio_dev);
+	int ret;
+
+	ret = regmap_write(data->regmap,
+		PAT9125_WRITE_PROTEC_REG,
+		PAT9125_DISABLE_WRITE_PROTECT_VAL);
+
+	if (!ret)
+		ret = regmap_write(data->regmap, reg_addr, reg_value);
+
+	/* Try to put back write protection everytime */
+	ret |= regmap_write(data->regmap,
+		PAT9125_WRITE_PROTEC_REG,
+		PAT9125_ENABLE_WRITE_PROTECT_VAL);

This ret |= trick leads to scrambled error codes.  So don't do it,
use two return variables and return the first one to give an
error if one occurs.

+
+	return ret;
+}
+/**
+ * pat9125_read_delta() - Read delta value, update delta & position data.
+ *
+ * @data: Driver's data structure.
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+static int pat9125_read_delta(struct pat9125_data *data)
+{
+	struct regmap *regmap = data->regmap;
+	int status = 0;
+	int val_x = 0;

Some of these are assigned anyway in all paths that use them.

+	int val_y = 0;
+	int val_high_nibbles = 0;
+	int ret;
+
+	ret = regmap_read(regmap, PAT9125_MOTION_STATUS_REG, &status);
+	if (ret < 0)
+		return ret;
+
+	/* Check if motion is detected */
+	if (status & PAT9125_VALID_MOTION_DATA_BIT) {
+		ret = regmap_read(regmap, PAT9125_DELTA_X_LO_REG, &val_x);
+		if (ret < 0)
+			return ret;
+
+		ret = regmap_read(regmap, PAT9125_DELTA_Y_LO_REG, &val_y);
+		if (ret < 0)
+			return ret;
+
+		ret = regmap_read(regmap, PAT9125_DELTA_XY_HI_REG,
+			&val_high_nibbles);
+		if (ret < 0)
+			return ret;
+
+		val_x |= (val_high_nibbles << 4) & 0xF00;
+		val_y |= (val_high_nibbles << 8) & 0xF00;
+		val_x = sign_extend32(val_x,
+			PAT9125_SAMPLED_VAL_BIT_SIZE - 1);
+		val_y = sign_extend32(val_y,
+			PAT9125_SAMPLED_VAL_BIT_SIZE - 1);
+		data->position_x += val_x;
+		data->position_y += val_y;
+	}
+	return 0;
+}
+
+/**
+ * pat9125_read_raw() - Sample and return the value(s)
+ * function to the associated channel info enum.
+ *
+ * @indio_dev:	Industrial I/O device.
+ * @chan:	Specification of a single channel.
+ * @val:	Contain the elements making up the returned value.
+ * @val2:	Not used.
+ * @mask:	(enum iio_chan_info_enum) Type of the info attribute.
+ *
+ * Zero will be returned on success, negative value otherwise.
+ **/
+static int pat9125_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct pat9125_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = pat9125_read_delta(data);
+		if (ret)
+			return ret;
+		switch (chan->channel2) {
+		case IIO_MOD_X:
+			*val = data->position_x;
+			return IIO_VAL_INT;
+		case IIO_MOD_Y:
+			*val = data->position_y;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->channel2) {
+		case IIO_MOD_X:
+			ret = regmap_read(data->regmap, PAT9125_RES_X_REG, val);
+			if (ret)
+				return ret;
+			else

These else against an error case are not common kernel idiom for error handling..

			if (ret)
				return ret;
			return IIO_VAL_INT;

+				return IIO_VAL_INT;
+		case IIO_MOD_Y:
+			ret = regmap_read(data->regmap, PAT9125_RES_Y_REG, val);
+			if (ret)
+				return ret;
+			else
+				return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
+/**
+ * pat9125_write_raw() - Write the value(s)
+ * function to the associated channel info enum.
+ *
+ * @indio_dev:	Industrial I/O device.
+ * @chan:	Specification of a single channel.
+ * @val:	Value write in the channel.
+ * @val2:	Not used.
+ * @mask:	(enum iio_chan_info_enum) Type of the info attribute.
+ *
+ * Zero will be returned on success, negative value otherwise.
+ **/

Kernel doc style is normally
*/ at end.

+static int pat9125_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, int val,
+			     int val2, long mask)
+{
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->channel2) {
+		case IIO_MOD_X:
+			ret = pat9125_write_pretected_reg(indio_dev,
+				PAT9125_RES_X_REG, val);
+			return ret;
+		case IIO_MOD_Y:
+			ret = pat9125_write_pretected_reg(indio_dev,
+				PAT9125_RES_Y_REG, val);
+			return ret;
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
+static irqreturn_t pat9125_threaded_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct pat9125_data *data = iio_priv(indio_dev);
+	u8 buf[16]; /* Payload: Pos_X (4) | Pos_Y (4) | Timestamp (8) */
+	int ret;
+	s64 timestamp;
+
+	data->sampling = true;
+	ret = pat9125_read_delta(data);
+	if (ret) {
+		dev_err(indio_dev->dev.parent, "Read delta failed %d\n", ret);
+		return IRQ_NONE;
+	}
+	timestamp = iio_get_time_ns(indio_dev);
+	*((s32 *)&buf[0]) = data->position_x;
+	*((s32 *)&buf[sizeof(s32)]) = data->position_y;
+	iio_push_to_buffers_with_timestamp(indio_dev, buf, timestamp);
+	iio_trigger_notify_done(indio_dev->trig);
+	return IRQ_HANDLED;
+}
+
+/**
+ * pat9125_threaded_event_handler() - Threaded motion detection event handler
+ * @irq: The irq being handled.
+ * @private: struct iio_device pointer for the device.
+ */
+static irqreturn_t pat9125_threaded_event_handler(int irq, void *private)
+{
+	struct iio_dev *indio_dev = private;
+	struct pat9125_data *data = iio_priv(indio_dev);
+
+	iio_trigger_poll_chained(data->indio_trig);
+	return IRQ_HANDLED;
+}
+
+/**
+ * pat9125_buffer_postenable() - Buffer post enable actions
+ *
+ * @indio_dev:	Industrial I/O device.
+ */
+static int pat9125_buffer_postenable(struct iio_dev *indio_dev)
+{
+	struct pat9125_data *data = iio_priv(indio_dev);
+	int ret = 0;

Check for any other cases of this.
Doesn't need to be assigned as is assigned in all paths.

+
+	ret = iio_triggered_buffer_postenable(indio_dev);
+	if (ret)
+		return ret;
+
+	/* Release interrupt pin on the device */
+	ret = pat9125_read_delta(data);
+
+	/* iio_trigger_detach_poll_func isn't reachable, so use this function */

Slightly odd comment.  We need to unwind iio_triggered_buffer_postenable, so
iio_triggered_buffer_predisable is the right function anyway..

+	if (ret)
+		ret = iio_triggered_buffer_predisable(indio_dev);
+
+	return ret;
+}
+
+static const struct iio_buffer_setup_ops pat9125_buffer_ops = {
+	.postenable = pat9125_buffer_postenable,
+};
+
+static const struct regmap_config pat9125_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static const struct iio_info pat9125_info = {
+	.read_raw = pat9125_read_raw,
+	.write_raw = pat9125_write_raw,
+};
+
+/*
+ * To detect if a new value is available, register status is checked. This
+ * method is safer than using a flag on GPIO IRQ to track event while sampling
+ * because falling edge is missed when device trig just after a read reg value
+ * (that happen for fast motions or high CPI setting).
+ *
+ * Note: To avoid infinite loop in "iio_trigger_notify_done" when it is not in
+ * buffer mode and kernel warning due to nested IRQ thread,
+ * this function must return 0.

Two things here.
For infinite loop prevention it would be cleaner to have an explicit
countdown in here (so let it loop N times).
I would also like to see a warning if it times out.

The point about not calling the iio_trigger_poll that would result from
a failed try reenable looks like a core bug to me.

I don't think try_reenable is ever called from interrupt context.
IIRC The interrupt code used to be a lot laxer on that so it probably
wouldn't have caused a problem originally but does now.
Hence please send a fix patch for the core code to switch to
the chained version.

+ */
+static int pat9125_trig_try_reenable(struct iio_trigger *trig)
+{
+	struct pat9125_data *data = iio_trigger_get_drvdata(trig);
+	struct regmap *regmap = data->regmap;
+	int status = 0;
+
+	if (data->sampling) {
+		regmap_read(regmap, PAT9125_MOTION_STATUS_REG, &status);
+		if (status & PAT9125_VALID_MOTION_DATA_BIT) {
+			data->sampling = false;
+			iio_trigger_poll_chained(data->indio_trig);
+			return 0;
+		}
+	}
+	data->sampling = false;
+	return 0;
+}
+
+static const struct iio_trigger_ops pat9125_trigger_ops = {
+	.try_reenable = pat9125_trig_try_reenable,
+};
+
+static int pat9125_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct pat9125_data *data;
+	struct iio_dev *indio_dev;
+	int ret, sensor_pid;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev) {
+		dev_err(&client->dev, "IIO device allocation failed\n");
+		return -ENOMEM;
+	}
+
+	data = iio_priv(indio_dev);
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->name = id->name;
+	indio_dev->channels = pat9125_channels;
+	indio_dev->num_channels = ARRAY_SIZE(pat9125_channels);
+	indio_dev->info = &pat9125_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	ret = devm_iio_triggered_buffer_setup(&client->dev, indio_dev, NULL,
+		pat9125_threaded_trigger_handler, &pat9125_buffer_ops);
+	if (ret) {
+		dev_err(&client->dev, "unable to setup triggered buffer\n");
+		return ret;
+	}
+
+	data->indio_trig = devm_iio_trigger_alloc(&client->dev, "%s-dev%d",
+		indio_dev->name, indio_dev->id);
+	if (!data->indio_trig)
+		return -ENOMEM;
+	data->indio_trig->dev.parent = &client->dev;
+	data->indio_trig->ops = &pat9125_trigger_ops;
+	iio_trigger_set_drvdata(data->indio_trig, data);
+	ret = devm_iio_trigger_register(&client->dev, data->indio_trig);
+	if (ret) {
+		dev_err(&client->dev, "unable to register trigger\n");
+		return ret;
+	}
+
+	data->regmap = devm_regmap_init_i2c(client, &pat9125_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		dev_err(&client->dev, "regmap init failed %ld\n",
+			PTR_ERR(data->regmap));
+		return PTR_ERR(data->regmap);
+	}
+
+	/* Check device ID */
+	ret = regmap_read(data->regmap, PAT9125_PRD_ID1_REG, &sensor_pid);
+	if (ret < 0) {
+		dev_err(&client->dev, "register 0x%x access failed %d\n",
+			PAT9125_PRD_ID1_REG, ret);
+		return ret;
+	}
+	if (sensor_pid != PAT9125_SENSOR_ID_VAL)
+		return -ENODEV;
+
+	/* Switch to bank0 (Magic number)*/
+	ret = regmap_write(data->regmap, 0x7F, 0x00);
+	if (ret < 0) {
+		dev_err(indio_dev->dev.parent, "register 0x%x access failed %d\n",
+			0x7F, ret);
+		return ret;
+	}
+
+	/* Software reset */
+	ret = regmap_write_bits(data->regmap,
+			      PAT9125_CONFIG_REG,
+			      PAT9125_RESET_BIT,
+			      1);
+	if (ret < 0) {
+		dev_err(&client->dev, "register 0x%x access failed %d\n",
+			PAT9125_CONFIG_REG, ret);
+		return ret;
+	}
+
+	msleep(20);
+
+	/* Init GPIO IRQ */
+	if (client->irq) {
+		ret = devm_request_threaded_irq(&client->dev,
+			client->irq,
+			NULL,
+			pat9125_threaded_event_handler,
+			IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+			"pat9125",
+			indio_dev);
+		if (ret) {
+			dev_err(&client->dev, "GPIO IRQ init failed\n");
+			return ret;
+		}
+	}
+
+	ret = devm_iio_device_register(&client->dev, indio_dev);
+	if (ret) {
+		dev_err(&client->dev, "IIO device register failed\n");
+		return ret;

Drop the return ret out of these brackets.  One of the static checkers
picks up on this sequence and will moan otherwise (can't recall which).

+	}
+
+	return 0;
+}
+
+static const struct i2c_device_id pat9125_id[] = {
+	{ "pat9125", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, pat9125_id);
+
+static const unsigned short normal_i2c[] = {
+	PAT9125_I2C_ADDR_HI,
+	PAT9125_I2C_ADDR_LO,
+	PAT9125_I2C_ADDR_NC,
+	I2C_CLIENT_END
+};
+
+static struct i2c_driver pat9125_driver = {
+	.driver = {
+		.name = "pat9125",
+	},
+	.probe = pat9125_probe,
+	.address_list = normal_i2c,
+	.id_table = pat9125_id,
+};
+
+module_i2c_driver(pat9125_driver);
+
+MODULE_AUTHOR("Alexandre Mergnat [off-list ref]");
+MODULE_DESCRIPTION("Optical Tracking sensor");
+MODULE_LICENSE("GPL");