Re: [PATCH v5 09/18] platform: chrome: sensorhub: Add FIFO support

[Jonathan Cameron]

On Fri, 15 Nov 2019 01:34:03 -0800
Gwendal Grignou <gwendal@xxxxxxxxxxxx> wrote:

> cros_ec_sensorhub registers a listener and query motion sense FIFO,
> spread to iio sensors registers.
> 
> To test, we can use libiio:
> iiod&
> iio_readdev -u ip:localhost -T 10000 -s 25 -b 16 cros-ec-gyro | od -x
> 
> Signed-off-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
Looks good.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>

> ---
> Changes in v5:
> - Use a goto in cros_ec_sensorhub_ring_handler to centralize error
>   handling
> - Use devm_add_action_or_reset to not need a .remove entry point for
>   cros_sensor_hub.
> - Fix logic error in cros_ec_sensorhub_register_push_data.
> - Update kernel_doc documentation.
> - Remve the need for comments in variable declaration section.
> Changes in v4:
> - Keep defining cros_ec_sensorhub in kernel-doc format
> - Fix logic error when checking if sensor index outside array.
> - Check patch with --strict option
>     Use sizeof(*obj) instead of sizeof(struct ...obj)
>     Alignement
>     Use uX instead of uintX_t
>     Use !ptr instead of ptr != NULL
> Changes in v3:
> - Do not use ret !=
> - Simplfy errpr handling by removing a goto
> - Fix doxygen comments
> - Replace suspend/resume entry points with regular driver entry point;
>   There was an issue in the past where the sensor stack was preventing
>   device to suspend, but the proper fix has been implemented in cros_ec
>   code (6ad16b78a039b "platform/chrome: don't report EC_MKBP_EVENT_SENSOR_FIFO as wakeup")
> - Reduce mutex scope by checking return code outside of it.
> Changes in v2:
> - Do not register a .remove routinge in plaform_driver. A
>   devm_action_add is added later patch IIO driver register their
> callback.
> - Remove double lines, add lines before return calls.
> - Handle FLUSH flag from EC.
> 
> - Use ktime_t for most timestamp measurements.
> - Add doxygen comments
> - Cleanup timestamp collection when processing FIFO.
> - Rename fifo_toggle to fifo_enable
> 
>  drivers/platform/chrome/Makefile              |   3 +-
>  drivers/platform/chrome/cros_ec_sensorhub.c   | 108 +++--
>  .../platform/chrome/cros_ec_sensorhub_ring.c  | 427 ++++++++++++++++++
>  .../linux/platform_data/cros_ec_sensorhub.h   |  91 ++++
>  4 files changed, 600 insertions(+), 29 deletions(-)
>  create mode 100644 drivers/platform/chrome/cros_ec_sensorhub_ring.c
> 
> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
> index a164c40dc099..cb709048c003 100644
> --- a/drivers/platform/chrome/Makefile
> +++ b/drivers/platform/chrome/Makefile
> @@ -17,7 +17,8 @@ obj-$(CONFIG_CROS_EC_PROTO)		+= cros_ec_proto.o cros_ec_trace.o
>  obj-$(CONFIG_CROS_KBD_LED_BACKLIGHT)	+= cros_kbd_led_backlight.o
>  obj-$(CONFIG_CROS_EC_CHARDEV)		+= cros_ec_chardev.o
>  obj-$(CONFIG_CROS_EC_LIGHTBAR)		+= cros_ec_lightbar.o
> -obj-$(CONFIG_CROS_EC_SENSORHUB)		+= cros_ec_sensorhub.o
> +cros_ec_sensorsupport-objs			:= cros_ec_sensorhub_ring.o cros_ec_sensorhub.o
> +obj-$(CONFIG_CROS_EC_SENSORHUB)		+= cros_ec_sensorsupport.o
>  obj-$(CONFIG_CROS_EC_VBC)		+= cros_ec_vbc.o
>  obj-$(CONFIG_CROS_EC_DEBUGFS)		+= cros_ec_debugfs.o
>  obj-$(CONFIG_CROS_EC_SYSFS)		+= cros_ec_sysfs.o
> diff --git a/drivers/platform/chrome/cros_ec_sensorhub.c b/drivers/platform/chrome/cros_ec_sensorhub.c
> index 85e3d3f25786..04fd60f747c0 100644
> --- a/drivers/platform/chrome/cros_ec_sensorhub.c
> +++ b/drivers/platform/chrome/cros_ec_sensorhub.c
> @@ -51,10 +51,8 @@ static int cros_ec_sensorhub_register(struct device *dev,
>  	int ret, i, id, sensor_num;
>  	struct cros_ec_dev *ec = sensorhub->ec;
>  	int sensor_type[MOTIONSENSE_TYPE_MAX] = { 0 };
> -	struct ec_params_motion_sense *params;
> -	struct ec_response_motion_sense *resp;
> -	struct cros_ec_command *msg;
>  	char *name;
> +	struct cros_ec_command *msg = sensorhub->msg;
>  
>  	sensor_num = cros_ec_get_sensor_count(ec);
>  	if (sensor_num < 0) {
> @@ -69,30 +67,21 @@ static int cros_ec_sensorhub_register(struct device *dev,
>  		return -EINVAL;
>  	}
>  
> -	/* Prepare a message to send INFO command to each sensor. */
> -	msg = kzalloc(sizeof(*msg) + max(sizeof(*params), sizeof(*resp)),
> -		      GFP_KERNEL);
> -	if (!msg)
> -		return -ENOMEM;
> -
>  	msg->version = 1;
> -	msg->command = EC_CMD_MOTION_SENSE_CMD + ec->cmd_offset;
> -	msg->outsize = sizeof(*params);
> -	msg->insize = sizeof(*resp);
> -	params = (struct ec_params_motion_sense *)msg->data;
> -	resp = (struct ec_response_motion_sense *)msg->data;
> +	msg->insize = sizeof(struct ec_response_motion_sense);
> +	msg->outsize = sizeof(struct ec_params_motion_sense);
>  
>  	id = 0;
>  	for (i = 0; i < sensor_num; i++) {
> -		params->cmd = MOTIONSENSE_CMD_INFO;
> -		params->info.sensor_num = i;
> +		sensorhub->params->cmd = MOTIONSENSE_CMD_INFO;
> +		sensorhub->params->info.sensor_num = i;
>  		ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
>  		if (ret < 0) {
>  			dev_warn(dev, "no info for EC sensor %d : %d/%d\n",
>  				 i, ret, msg->result);
>  			continue;
>  		}
> -		switch (resp->info.type) {
> +		switch (sensorhub->resp->info.type) {
>  		case MOTIONSENSE_TYPE_ACCEL:
>  			name = "cros-ec-accel";
>  			break;
> @@ -115,14 +104,15 @@ static int cros_ec_sensorhub_register(struct device *dev,
>  			name = "cros-ec-activity";
>  			break;
>  		default:
> -			dev_warn(dev, "unknown type %d\n", resp->info.type);
> +			dev_warn(dev, "unknown type %d\n",
> +				 sensorhub->resp->info.type);
>  			continue;
>  		}
>  		ret = cros_ec_sensorhub_allocate_single_sensor(dev, name, i);
>  		if (ret)
> -			goto error;
> +			return ret;
>  
> -		sensor_type[resp->info.type]++;
> +		sensor_type[sensorhub->resp->info.type]++;
>  	}
>  
>  	if (sensor_type[MOTIONSENSE_TYPE_ACCEL] >= 2)
> @@ -133,14 +123,9 @@ static int cros_ec_sensorhub_register(struct device *dev,
>  		ret = cros_ec_sensorhub_allocate_single_sensor(dev,
>  							"cros-ec-lid-angle", 0);
>  		if (ret)
> -			goto error;
> +			return ret;
>  	}
> -	kfree(msg);
>  	return 0;
> -
> -error:
> -	kfree(msg);
> -	return ret;
>  }
>  
>  static int cros_ec_sensorhub_probe(struct platform_device *sensorhub_pdev)
> @@ -148,13 +133,29 @@ static int cros_ec_sensorhub_probe(struct platform_device *sensorhub_pdev)
>  	struct device *dev = &sensorhub_pdev->dev;
>  	struct cros_ec_dev *ec = dev_get_drvdata(dev->parent);
>  	int ret, i;
> -	struct cros_ec_sensorhub *data =
> -		devm_kzalloc(dev, sizeof(struct cros_ec_sensorhub), GFP_KERNEL);
> +	struct cros_ec_sensorhub *data;
> +	struct cros_ec_command *msg;
>  
> +	msg = devm_kzalloc(dev, sizeof(struct cros_ec_command) +
> +			max((u16)sizeof(struct ec_params_motion_sense),
> +			    ec->ec_dev->max_response), GFP_KERNEL);
> +	if (!msg)
> +		return -ENOMEM;
> +
> +	msg->command = EC_CMD_MOTION_SENSE_CMD + ec->cmd_offset;
> +
> +	data = devm_kzalloc(dev, sizeof(struct cros_ec_sensorhub), GFP_KERNEL);
>  	if (!data)
>  		return -ENOMEM;
>  
> +	data->dev = dev;
>  	data->ec = ec;
> +
> +	mutex_init(&data->cmd_lock);
> +	data->msg = msg;
> +	data->params = (struct ec_params_motion_sense *)msg->data;
> +	data->resp = (struct ec_response_motion_sense *)msg->data;
> +
>  	dev_set_drvdata(dev, data);
>  
>  	/* Check whether this EC is a sensor hub. */
> @@ -179,12 +180,63 @@ static int cros_ec_sensorhub_probe(struct platform_device *sensorhub_pdev)
>  		}
>  	}
>  
> +	/*
> +	 * If the EC does not have a FIFO, the sensors will query their data
> +	 * themselves via sysfs or a software trigger.
> +	 */
> +	if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE_FIFO)) {
> +		ret = cros_ec_sensorhub_ring_add(data);
> +		if (ret)
> +			return ret;
> +		/*
> +		 * The msg and its data is not under the control of the ring
> +		 * handler.
> +		 */
> +		return devm_add_action_or_reset(dev,
> +						cros_ec_sensorhub_ring_remove,
> +						data);
> +	}
> +
> +	return 0;
> +}
> +
> +#if CONFIG_PM_SLEEP
> +/*
> + * When the EC is suspending, we must stop sending interrupt,
> + * we may use the same interrupt line for waking up the device.
> + * Tell the EC to stop sending non-interrupt event on the iio ring.
> + */
> +static int cros_ec_ring_suspend(struct device *dev)
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct cros_ec_sensorhub *sensorhub = platform_get_drvdata(pdev);
> +	struct cros_ec_dev *ec = sensorhub->ec;
> +
> +	if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE_FIFO))
> +		return cros_ec_sensorhub_ring_fifo_enable(sensorhub, false);
>  	return 0;
>  }
>  
> +static int cros_ec_ring_resume(struct device *dev)
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct cros_ec_sensorhub *sensorhub = platform_get_drvdata(pdev);
> +	struct cros_ec_dev *ec = sensorhub->ec;
> +
> +	if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE_FIFO))
> +		return cros_ec_sensorhub_ring_fifo_enable(sensorhub, true);
> +	return 0;
> +}
> +#endif
> +
> +static SIMPLE_DEV_PM_OPS(cros_ec_sensorhub_ring_pm_ops,
> +		cros_ec_ring_suspend,
> +		cros_ec_ring_resume);
> +
>  static struct platform_driver cros_ec_sensorhub_driver = {
>  	.driver = {
>  		.name = DRV_NAME,
> +		.pm = &cros_ec_sensorhub_ring_pm_ops,
>  	},
>  	.probe = cros_ec_sensorhub_probe,
>  };
> diff --git a/drivers/platform/chrome/cros_ec_sensorhub_ring.c b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
> new file mode 100644
> index 000000000000..32333f67e26a
> --- /dev/null
> +++ b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
> @@ -0,0 +1,427 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * cros_ec_sensorhub_ring - Driver for Chrome OS EC Sensor hub FIFO.
> + *
> + * Copyright 2019 Google LLC
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/iio/iio.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/cros_ec.h>
> +#include <linux/module.h>
> +#include <linux/platform_data/cros_ec_commands.h>
> +#include <linux/platform_data/cros_ec_proto.h>
> +#include <linux/platform_data/cros_ec_sensorhub.h>
> +#include <linux/platform_device.h>
> +#include <linux/sort.h>
> +#include <linux/slab.h>
> +
> +static inline int cros_sensorhub_send_sample(
> +		struct cros_ec_sensorhub *sensorhub,
> +		struct cros_ec_sensors_ring_sample *sample)
> +{
> +	int id = sample->sensor_id;
> +	cros_ec_sensorhub_push_data_cb_t cb;
> +	struct iio_dev *indio_dev;
> +
> +	if (id > CROS_EC_SENSOR_MAX)
> +		return -EINVAL;
> +
> +	cb = sensorhub->push_data[id].push_data_cb;
> +	if (!cb)
> +		return 0;
> +
> +	indio_dev = sensorhub->push_data[id].indio_dev;
> +
> +	if (sample->flag & MOTIONSENSE_SENSOR_FLAG_FLUSH)
> +		return 0;
> +
> +	return cb(indio_dev, sample->vector, sample->timestamp);
> +}
> +
> +/**
> + * cros_ec_sensorhub_register_push_data() - register the callback to the hub.
> + *
> + * @sensorhub : Sensor Hub object
> + * @sensor_num : The sensor the caller is interested in.
> + * @indio_dev : The iio device to use when a sample arrives.
> + * @cb : The callback to call when a sample arrives.
> + *
> + * The callback cb will be used by cros_ec_sensorhub_ring to distribute events
> + * from the EC.
> + *
> + * Return: 0 when callback is registered.
> + */
> +int cros_ec_sensorhub_register_push_data(struct cros_ec_sensorhub *sensorhub,
> +					 u8 sensor_num,
> +					 struct iio_dev *indio_dev,
> +					 cros_ec_sensorhub_push_data_cb_t cb)
> +{
> +	if (sensor_num >= CROS_EC_SENSOR_PDEV_MAX)
> +		return -EINVAL;
> +	if (sensorhub->push_data[sensor_num].indio_dev)
> +		return -EINVAL;
> +
> +	sensorhub->push_data[sensor_num].indio_dev = indio_dev;
> +	sensorhub->push_data[sensor_num].push_data_cb = cb;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(cros_ec_sensorhub_register_push_data);
> +
> +void cros_ec_sensorhub_unregister_push_data(struct cros_ec_sensorhub *sensorhub,
> +					    u8 sensor_num)
> +{
> +	sensorhub->push_data[sensor_num].indio_dev = NULL;
> +	sensorhub->push_data[sensor_num].push_data_cb = NULL;
> +}
> +EXPORT_SYMBOL_GPL(cros_ec_sensorhub_unregister_push_data);
> +
> +/**
> + * cros_ec_sensorhub_ring_fifo_enable() - Enable or disable interrupt generation
> + *  for FIFO events.
> + * @sensorhub : Sensor Hub object
> + * @on : true when events are requested.
> + *
> + * To be called before sleeping or when noone is listening.
> + * Return: 0 on success.
> + */
> +int cros_ec_sensorhub_ring_fifo_enable(struct cros_ec_sensorhub *sensorhub,
> +				       bool on)
> +{
> +	int ret;
> +
> +	mutex_lock(&sensorhub->cmd_lock);
> +	sensorhub->params->cmd = MOTIONSENSE_CMD_FIFO_INT_ENABLE;
> +	sensorhub->params->fifo_int_enable.enable = on;
> +
> +	sensorhub->msg->outsize = sizeof(struct ec_params_motion_sense);
> +	sensorhub->msg->insize = sizeof(struct ec_response_motion_sense);
> +
> +	ret = cros_ec_cmd_xfer_status(sensorhub->ec->ec_dev, sensorhub->msg);
> +	mutex_unlock(&sensorhub->cmd_lock);
> +
> +	/* We expect to receive a payload of 4 bytes, ignore. */
> +	if (ret > 0)
> +		ret = 0;
> +
> +	return ret;
> +}
> +
> +/**
> + * cros_ec_ring_process_event() - process one EC FIFO event
> + *
> + * @sensorhub: Sensorhub object.
> + * @fifo_info: fifo information from the EC (includes b point, EC timebase).
> + * @fifo_timestamp: EC IRQ, kernel timebase (aka c)
> + * @current_timestamp: calculated event timestamp, kernel timebase (aka a')
> + * @in: incoming FIFO event from EC (includes a point, EC timebase)
> + * @out: outgoing event to user space (includes a')
> + *
> + * Process one EC event, add it in the ring if necessary.
> + *
> + * Return: true if out event has been populated.
> + */
> +static bool cros_ec_ring_process_event(struct cros_ec_sensorhub *sensorhub,
> +				const struct cros_ec_fifo_info *fifo_info,
> +				const ktime_t fifo_timestamp,
> +				ktime_t *current_timestamp,
> +				struct ec_response_motion_sensor_data *in,
> +				struct cros_ec_sensors_ring_sample *out)
> +{
> +	int axis, async_flags;
> +	const s64 now = cros_ec_get_time_ns();
> +
> +	/* Do not populate the filter based on asynchronous events. */
> +	async_flags = in->flags &
> +		(MOTIONSENSE_SENSOR_FLAG_ODR | MOTIONSENSE_SENSOR_FLAG_FLUSH);
> +
> +	if (in->flags & MOTIONSENSE_SENSOR_FLAG_TIMESTAMP && !async_flags) {
> +		s64 a = in->timestamp;
> +		s64 b = fifo_info->info.timestamp;
> +		s64 c = fifo_timestamp;
> +		s64 new_timestamp;
> +
> +		/*
> +		 * disable filtering since we might add more jitter
> +		 * if b is in a random point in time
> +		 */
> +		new_timestamp = c - b * 1000 + a * 1000;
> +
> +		/*
> +		 * The timestamp can be stale if we had to use the fifo
> +		 * info timestamp.
> +		 */
> +		if (new_timestamp - *current_timestamp > 0)
> +			*current_timestamp = new_timestamp;
> +	}
> +
> +	if (in->flags & MOTIONSENSE_SENSOR_FLAG_FLUSH) {
> +		out->sensor_id = in->sensor_num;
> +		out->timestamp = *current_timestamp;
> +		out->flag = in->flags;
> +		/*
> +		 * No other payload information provided with
> +		 * flush ack.
> +		 */
> +		return true;
> +	}
> +
> +	if (in->flags & MOTIONSENSE_SENSOR_FLAG_TIMESTAMP)
> +		/* If we just have a timestamp, skip this entry. */
> +		return false;
> +
> +	/* Regular sample */
> +	out->sensor_id = in->sensor_num;
> +	if (*current_timestamp - now > 0) {
> +		/* If the timestamp is in the future. */
> +		out->timestamp = now;
> +	} else {
> +		out->timestamp = *current_timestamp;
> +	}
> +
> +	out->flag = in->flags;
> +	for (axis = 0; axis < 3; axis++)
> +		out->vector[axis] = in->data[axis];
> +
> +	return true;
> +}
> +
> +/**
> + * cros_ec_sensorhub_ring_handler() - the trigger handler function
> + *
> + * @sensorhub: device information.
> + *
> + * Called by the notifier, process the EC sensor FIFO queue.
> + */
> +static void cros_ec_sensorhub_ring_handler(struct cros_ec_sensorhub *sensorhub)
> +{
> +	struct cros_ec_fifo_info *fifo_info = &sensorhub->fifo_info;
> +	struct cros_ec_dev *ec = sensorhub->ec;
> +	ktime_t fifo_timestamp, current_timestamp;
> +	int i, j, number_data, ret;
> +	unsigned long sensor_mask = 0;
> +	struct ec_response_motion_sensor_data *in;
> +	struct cros_ec_sensors_ring_sample *out, *last_out;
> +
> +	mutex_lock(&sensorhub->cmd_lock);
> +
> +	/* Get FIFO information if there are lost vectors. */
> +	if (fifo_info->info.total_lost) {
> +		/* Need to retrieve the number of lost vectors per sensor */
> +		sensorhub->params->cmd = MOTIONSENSE_CMD_FIFO_INFO;
> +		sensorhub->msg->outsize = 1;
> +		sensorhub->msg->insize =
> +			sizeof(struct ec_response_motion_sense_fifo_info) +
> +			sizeof(u16) * CROS_EC_SENSOR_MAX;
> +
> +		if (cros_ec_cmd_xfer_status(ec->ec_dev, sensorhub->msg) < 0)
> +			goto error;
> +
> +		memcpy(fifo_info, &sensorhub->resp->fifo_info,
> +		       sizeof(*fifo_info));
> +
> +		/*
> +		 * Update collection time, will not be as precise as the
> +		 * non-error case.
> +		 */
> +		fifo_timestamp = cros_ec_get_time_ns();
> +	} else {
> +		fifo_timestamp = sensorhub->fifo_timestamp[
> +			CROS_EC_SENSOR_NEW_TS];
> +	}
> +
> +	if (fifo_info->info.count > sensorhub->fifo_size ||
> +	    fifo_info->info.size != sensorhub->fifo_size) {
> +		dev_warn(sensorhub->dev,
> +			 "Mismatch EC data: count %d, size %d - expected %d",
> +			 fifo_info->info.count, fifo_info->info.size,
> +			 sensorhub->fifo_size);
> +		goto error;
> +	}
> +
> +	/* Copy elements in the main fifo */
> +	current_timestamp = sensorhub->fifo_timestamp[CROS_EC_SENSOR_LAST_TS];
> +	out = sensorhub->ring;
> +	for (i = 0; i < fifo_info->info.count; i += number_data) {
> +		sensorhub->params->cmd = MOTIONSENSE_CMD_FIFO_READ;
> +		sensorhub->params->fifo_read.max_data_vector =
> +			fifo_info->info.count - i;
> +		sensorhub->msg->outsize =
> +			sizeof(struct ec_params_motion_sense);
> +		sensorhub->msg->insize =
> +			sizeof(sensorhub->resp->fifo_read) +
> +			sensorhub->params->fifo_read.max_data_vector *
> +			  sizeof(struct ec_response_motion_sensor_data);
> +		ret = cros_ec_cmd_xfer_status(ec->ec_dev, sensorhub->msg);
> +		if (ret < 0) {
> +			dev_warn(sensorhub->dev, "Fifo error: %d\n", ret);
> +			break;
> +		}
> +		number_data = sensorhub->resp->fifo_read.number_data;
> +		if (number_data == 0) {
> +			dev_dbg(sensorhub->dev, "Unexpected empty FIFO\n");
> +			break;
> +		}
> +		if (number_data > fifo_info->info.count - i) {
> +			dev_warn(sensorhub->dev,
> +				 "Invalid EC data: too many entry received: %d, expected %d",
> +				 number_data, fifo_info->info.count - i);
> +			break;
> +		}
> +		if (out + number_data >
> +		    sensorhub->ring + fifo_info->info.count) {
> +			dev_warn(sensorhub->dev,
> +				 "Too many samples: %d (%zd data) to %d entries for expected %d entries",
> +				 i, out - sensorhub->ring, i + number_data,
> +				 fifo_info->info.count);
> +			break;
> +		}
> +
> +		for (in = sensorhub->resp->fifo_read.data, j = 0;
> +		     j < number_data; j++, in++) {
> +			if (cros_ec_ring_process_event(sensorhub, fifo_info,
> +						       fifo_timestamp,
> +						       &current_timestamp,
> +						       in, out)) {
> +				sensor_mask |= (1 << in->sensor_num);
> +				out++;
> +			}
> +		}
> +	}
> +	mutex_unlock(&sensorhub->cmd_lock);
> +	last_out = out;
> +
> +	if (out == sensorhub->ring)
> +		/* Unexpected empty FIFO. */
> +		goto ring_handler_end;
> +
> +	/*
> +	 * Check if current_timestamp is ahead of the last sample.
> +	 * Normally, the EC appends a timestamp after the last sample, but if
> +	 * the AP is slow to respond to the IRQ, the EC may have added new
> +	 * samples. Use the FIFO info timestamp as last timestamp then.
> +	 */
> +	if ((last_out - 1)->timestamp == current_timestamp)
> +		current_timestamp = fifo_timestamp;
> +
> +	/* Warn on lost samples. */
> +	for_each_set_bit(i, &sensor_mask, BITS_PER_LONG) {
> +		int total_lost = fifo_info->info.total_lost;
> +
> +		if (total_lost) {
> +			int lost = fifo_info->lost[i];
> +
> +			if (lost) {
> +				dev_warn_ratelimited(sensorhub->dev,
> +						     "Sensor %d: lost: %d out of %d\n",
> +						     i, lost, total_lost);
> +			}
> +		}
> +	}
> +
> +	/* push the event into the kfifo */
> +	for (out = sensorhub->ring; out < last_out; out++)
> +		cros_sensorhub_send_sample(sensorhub, out);
> +
> +ring_handler_end:
> +	sensorhub->fifo_timestamp[CROS_EC_SENSOR_LAST_TS] = current_timestamp;
> +	return;
> +
> +error:
> +	mutex_unlock(&sensorhub->cmd_lock);
> +	return;
> +}
> +
> +static int cros_ec_sensorhub_event(struct notifier_block *nb,
> +				   unsigned long queued_during_suspend,
> +				   void *_notify)
> +{
> +	struct cros_ec_sensorhub *sensorhub;
> +	struct cros_ec_device *ec_dev;
> +
> +	sensorhub = container_of(nb, struct cros_ec_sensorhub, notifier);
> +	ec_dev = sensorhub->ec->ec_dev;
> +
> +	if (ec_dev->event_data.event_type != EC_MKBP_EVENT_SENSOR_FIFO)
> +		return NOTIFY_DONE;
> +
> +	if (ec_dev->event_size != sizeof(ec_dev->event_data.data.sensor_fifo)) {
> +		dev_warn(ec_dev->dev, "Invalid fifo info size\n");
> +		return NOTIFY_DONE;
> +	}
> +
> +	if (queued_during_suspend)
> +		return NOTIFY_OK;
> +
> +	sensorhub->fifo_info.info = ec_dev->event_data.data.sensor_fifo.info;
> +	sensorhub->fifo_timestamp[CROS_EC_SENSOR_NEW_TS] =
> +		ec_dev->last_event_time;
> +	cros_ec_sensorhub_ring_handler(sensorhub);
> +
> +	return NOTIFY_OK;
> +}
> +
> +/**
> + * cros_ec_sensorhub_ring_add() - Add/Remove the fifo functionality if the EC
> + *  supports it.
> + *
> + * @sensorhub : Sensor Hub object
> + *
> + * Return: 0 on success.
> + */
> +int cros_ec_sensorhub_ring_add(struct cros_ec_sensorhub *sensorhub)
> +{
> +	struct cros_ec_dev *ec = sensorhub->ec;
> +	int ret;
> +
> +	/* Retrieve FIFO information */
> +	sensorhub->msg->version = 2;
> +	sensorhub->params->cmd = MOTIONSENSE_CMD_FIFO_INFO;
> +	sensorhub->msg->outsize = 1;
> +	sensorhub->msg->insize =
> +		sizeof(struct ec_response_motion_sense_fifo_info) +
> +		sizeof(u16) * CROS_EC_SENSOR_MAX;
> +
> +	ret = cros_ec_cmd_xfer_status(ec->ec_dev, sensorhub->msg);
> +	if (ret < 0)
> +		return ret;
> +
> +	/*
> +	 * Allocate the full fifo.
> +	 * We need to copy the whole FIFO to set timestamps properly *
> +	 */
> +	sensorhub->fifo_size = sensorhub->resp->fifo_info.size;
> +	sensorhub->ring = devm_kcalloc(sensorhub->dev, sensorhub->fifo_size,
> +				       sizeof(*sensorhub->ring), GFP_KERNEL);
> +	if (!sensorhub->ring)
> +		return -ENOMEM;
> +
> +	sensorhub->fifo_timestamp[CROS_EC_SENSOR_LAST_TS] =
> +		cros_ec_get_time_ns();
> +
> +	/* register the notifier that will act as a top half interrupt. */
> +	sensorhub->notifier.notifier_call = cros_ec_sensorhub_event;
> +	ret = blocking_notifier_chain_register(&ec->ec_dev->event_notifier,
> +					       &sensorhub->notifier);
> +	if (ret < 0) {
> +		dev_warn(sensorhub->dev, "failed to register notifier\n");
> +		return ret;
> +	}
> +
> +	/* Start collection samples. */
> +	return cros_ec_sensorhub_ring_fifo_enable(sensorhub, true);
> +}
> +
> +void cros_ec_sensorhub_ring_remove(void *arg)
> +{
> +	struct cros_ec_sensorhub *sensorhub = arg;
> +	struct cros_ec_device *ec_dev = sensorhub->ec->ec_dev;
> +
> +	/* Disable the ring, prevent EC interrupt to the AP for nothing. */
> +	cros_ec_sensorhub_ring_fifo_enable(sensorhub, false);
> +	blocking_notifier_chain_unregister(&ec_dev->event_notifier,
> +					   &sensorhub->notifier);
> +}
> diff --git a/include/linux/platform_data/cros_ec_sensorhub.h b/include/linux/platform_data/cros_ec_sensorhub.h
> index 7421c956246f..5aaaa6cb012a 100644
> --- a/include/linux/platform_data/cros_ec_sensorhub.h
> +++ b/include/linux/platform_data/cros_ec_sensorhub.h
> @@ -8,8 +8,20 @@
>  #ifndef __LINUX_PLATFORM_DATA_CROS_EC_SENSORHUB_H
>  #define __LINUX_PLATFORM_DATA_CROS_EC_SENSORHUB_H
>  
> +#include <linux/ktime.h>
> +#include <linux/mutex.h>
> +#include <linux/notifier.h>
>  #include <linux/platform_data/cros_ec_commands.h>
>  
> +/* Maximal number of sensors supported by the EC. */
> +#define CROS_EC_SENSOR_MAX 16
> +
> +/*
> + * Maximal number of sensors supported by the hub:
> + * We add one for the lid angle inclinometer sensor.
> + */
> +#define CROS_EC_SENSOR_PDEV_MAX (CROS_EC_SENSOR_MAX + 1)
> +
>  /**
>   * struct cros_ec_sensor_platform - ChromeOS EC sensor platform information.
>   * @sensor_num: Id of the sensor, as reported by the EC.
> @@ -18,13 +30,92 @@ struct cros_ec_sensor_platform {
>  	u8 sensor_num;
>  };
>  
> +struct iio_dev;
> +
> +/**
> + * typedef cros_ec_sensorhub_push_data_cb_t - Callback function to send datum
> + *     to specific sensors
> + *
> + * @indio_dev: The IIO device that will process the sample.
> + * @data: vector array of the ring sample.
> + * @timestamp: Timestamp in host timespace when the sample was acquired by
> + *             the EC.
> + */
> +typedef int (*cros_ec_sensorhub_push_data_cb_t)(struct iio_dev *indio_dev,
> +						s16 *data,
> +						s64 timestamp);
> +
> +struct cros_ec_sensorhub_sensor_push_data {
> +	struct iio_dev *indio_dev;
> +	cros_ec_sensorhub_push_data_cb_t push_data_cb;
> +};
> +
> +enum {
> +	CROS_EC_SENSOR_LAST_TS,
> +	CROS_EC_SENSOR_NEW_TS,
> +	CROS_EC_SENSOR_ALL_TS
> +};
> +
> +struct __ec_todo_packed cros_ec_fifo_info {
> +	struct ec_response_motion_sense_fifo_info info;
> +	u16    lost[CROS_EC_SENSOR_MAX];
> +};
> +
> +struct cros_ec_sensors_ring_sample {
> +	u8  sensor_id;
> +	u8  flag;
> +	s16 vector[3];
> +	s64 timestamp;
> +} __packed;
> +
>  /**
>   * struct cros_ec_sensorhub - Sensor Hub device data.
>   *
> + * @dev:          Device object, mostly used for logging.
>   * @ec:           Embedded Controller where the hub is located.
> + * @msg: Structure to send FIFO requests.
> + * @params: pointer to parameters in msg.
> + * @resp: pointer to responses in msg.
> + * @cmd_lock : lock for sending msg.
> + * @notifier: Notifier to kick the FIFO interrupt.
> + * @ring: Preprocessed ring to store events.
> + * @fifo_timestamp: array for event timestamp and spreading.
> + * @fifo_info: copy of FIFO information coming from the EC.
> + * @fifo_size: size of the ring.
> + * @push_data: array of callback to send datums to iio sensor object.
>   */
>  struct cros_ec_sensorhub {
> +	struct device *dev;
>  	struct cros_ec_dev *ec;
> +
> +	struct cros_ec_command *msg;
> +	struct ec_params_motion_sense *params;
> +	struct ec_response_motion_sense *resp;
> +	struct mutex cmd_lock;
> +
> +	struct notifier_block notifier;
> +
> +	struct cros_ec_sensors_ring_sample *ring;
> +
> +	ktime_t fifo_timestamp[CROS_EC_SENSOR_ALL_TS];
> +	struct cros_ec_fifo_info fifo_info;
> +	int    fifo_size;
> +
> +	struct cros_ec_sensorhub_sensor_push_data push_data[
> +		CROS_EC_SENSOR_PDEV_MAX];
>  };
>  
> +int cros_ec_sensorhub_register_push_data(struct cros_ec_sensorhub *sensorhub,
> +					 u8 sensor_num,
> +					 struct iio_dev *indio_dev,
> +					 cros_ec_sensorhub_push_data_cb_t cb);
> +
> +void cros_ec_sensorhub_unregister_push_data(struct cros_ec_sensorhub *sensorhub,
> +					    u8 sensor_num);
> +
> +int cros_ec_sensorhub_ring_add(struct cros_ec_sensorhub *sensorhub);
> +void cros_ec_sensorhub_ring_remove(void *arg);
> +int cros_ec_sensorhub_ring_fifo_enable(struct cros_ec_sensorhub *sensorhub,
> +				       bool on);
> +
>  #endif   /* __LINUX_PLATFORM_DATA_CROS_EC_SENSORHUB_H */