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Date:   Thu, 29 Aug 2019 20:34:37 +0900
From:   William Breathitt Gray <vilhelm.gray@gmail.com>
To:     Fabien Lahoudere <fabien.lahoudere@collabora.com>
Cc:     gwendal@chromium.org, egranata@chromium.org, kernel@collabora.com,
        Jonathan Corbet <corbet@lwn.net>,
        Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Guenter Roeck <groeck@chromium.org>,
        Jonathan Cameron <jic23@kernel.org>,
        Hartmut Knaack <knaack.h@gmx.de>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        Lee Jones <lee.jones@linaro.org>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Nick Vaccaro <nvaccaro@chromium.org>,
        linux-iio@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/1] counter: cros_ec: Add synchronization sensor
Message-ID: <20190829112001.GA644343@icarus>
References: <cover.1566563833.git.fabien.lahoudere@collabora.com>
 <d985a8a811996148e8cda78b9fe47bb87b884b56.1566563833.git.fabien.lahoudere@collabora.com>
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On Fri, Aug 23, 2019 at 02:41:27PM +0200, Fabien Lahoudere wrote:
> From: Gwendal Grignou <gwendal@chromium.org>
> 
> EC returns a counter when there is an event on camera vsync.
> This patch comes from chromeos kernel 4.4
> 
> Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
> Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.com>
> 
> CROS EC sync sensor was originally designed as an IIO device.
> Now that the counter subsystem will replace IIO_COUNTER, we
> have to implement a new way to get sync count.
> 
> Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.com>
> ---
>  Documentation/driver-api/generic-counter.rst  |   3 +
>  MAINTAINERS                                   |   7 +
>  drivers/counter/Kconfig                       |   9 +
>  drivers/counter/Makefile                      |   1 +
>  drivers/counter/counter.c                     |   2 +
>  drivers/counter/cros_ec_sensors_sync.c        | 208 ++++++++++++++++++
>  .../cros_ec_sensors/cros_ec_sensors_core.c    |   1 +
>  drivers/mfd/cros_ec_dev.c                     |   3 +
>  include/linux/counter.h                       |   1 +
>  9 files changed, 235 insertions(+)
>  create mode 100644 drivers/counter/cros_ec_sensors_sync.c
> 
> diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst
> index 8382f01a53e3..beb80714ac8b 100644
> --- a/Documentation/driver-api/generic-counter.rst
> +++ b/Documentation/driver-api/generic-counter.rst
> @@ -44,6 +44,9 @@ Counter interface provides the following available count data types:
>  * COUNT_POSITION:
>    Unsigned integer value representing position.
>  
> +* COUNT_TALLY:
> +  Unsigned integer value representing tally.
> +
>  A Count has a count function mode which represents the update behavior
>  for the count data. The Generic Counter interface provides the following
>  available count function modes:
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e60f5c361969..83bd291d103e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3902,6 +3902,13 @@ R:	Guenter Roeck <groeck@chromium.org>
>  F:	Documentation/devicetree/bindings/sound/google,cros-ec-codec.txt
>  F:	sound/soc/codecs/cros_ec_codec.*
>  
> +CHROMEOS EC COUNTER DRIVER
> +M:	Fabien Lahoudere <fabien.lahoudere@collabora.com>
> +M:	William Breathitt Gray <vilhelm.gray@gmail.com>

No need to include me here since I'm already listed as the maintainer of
the Counter subsystem in its respective entry.

> +L:	linux-iio@vger.kernel.org
> +S:	Maintained
> +F:	drivers/counter/cros_ec_sensors_sync.c
> +
>  CIRRUS LOGIC AUDIO CODEC DRIVERS
>  M:	Brian Austin <brian.austin@cirrus.com>
>  M:	Paul Handrigan <Paul.Handrigan@cirrus.com>
> diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
> index 2967d0a9ff91..22287f5715e5 100644
> --- a/drivers/counter/Kconfig
> +++ b/drivers/counter/Kconfig
> @@ -59,4 +59,13 @@ config FTM_QUADDEC
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ftm-quaddec.
>  
> +config IIO_CROS_EC_SENSORS_SYNC
> +	tristate "ChromeOS EC Counter Sensors"
> +	depends on IIO_CROS_EC_SENSORS_CORE && IIO
> +	help
> +	  Module to handle synchronisation sensors presented by the ChromeOS EC
> +	  Sensor hub.
> +	  Synchronisation sensors are counter sensors triggered when events
> +	  occurs from other subsystems.
> +
>  endif # COUNTER
> diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
> index 40d35522937d..6fe4c98a446f 100644
> --- a/drivers/counter/Makefile
> +++ b/drivers/counter/Makefile
> @@ -9,3 +9,4 @@ obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
>  obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
>  obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
>  obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
> +obj-$(CONFIG_IIO_CROS_EC_SENSORS_SYNC) += cros_ec_sensors_sync.o
> diff --git a/drivers/counter/counter.c b/drivers/counter/counter.c
> index 106bc7180cd8..53525b109094 100644
> --- a/drivers/counter/counter.c
> +++ b/drivers/counter/counter.c
> @@ -261,6 +261,7 @@ void counter_count_read_value_set(struct counter_count_read_value *const val,
>  {
>  	switch (type) {
>  	case COUNTER_COUNT_POSITION:
> +	case COUNTER_COUNT_TALLY:
>  		val->len = sprintf(val->buf, "%lu\n", *(unsigned long *)data);
>  		break;
>  	default:
> @@ -290,6 +291,7 @@ int counter_count_write_value_get(void *const data,
>  
>  	switch (type) {
>  	case COUNTER_COUNT_POSITION:
> +	case COUNTER_COUNT_TALLY:
>  		err = kstrtoul(val->buf, 0, data);
>  		if (err)
>  			return err;

Dedicate the core counter subsystem related changes to their own patch
so that we can commit them separately. That'll make it easier both to
evaluate the changes and debug later by keeping the history clear.

> diff --git a/drivers/counter/cros_ec_sensors_sync.c b/drivers/counter/cros_ec_sensors_sync.c
> new file mode 100644
> index 000000000000..b6f5e2c6da9f
> --- /dev/null
> +++ b/drivers/counter/cros_ec_sensors_sync.c
> @@ -0,0 +1,208 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver of counter incremented after events on interrupt line in EC.
> + *
> + * Copyright 2018 Google, Inc
> + */
> +
> +#include <linux/device.h>
> +#include <linux/counter.h>
> +#include <linux/iio/common/cros_ec_sensors_core.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/cros_ec.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +#define DRV_NAME "cros-ec-sync"
> +
> +/*
> + * One channel for counter, the other for timestamp.
> + */
> +#define MAX_CHANNELS (1)
> +
> +/* State data for ec_sensors iio driver. */
> +struct cros_ec_sensors_sync_state {
> +	/* Shared by all sensors */
> +	struct cros_ec_sensors_core_state core;
> +	struct counter_device counter;
> +	struct iio_chan_spec channels[MAX_CHANNELS];
> +};
> +
> +static int cros_ec_sensors_sync_read(struct iio_dev *indio_dev,
> +				     struct iio_chan_spec const *chan,
> +				     int *val, int *val2, long mask)
> +{
> +	struct cros_ec_sensors_sync_state *st = iio_priv(indio_dev);
> +	u16 data;
> +	int ret;
> +
> +	mutex_lock(&st->core.cmd_lock);
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = cros_ec_sensors_read_cmd(indio_dev, BIT(0), &data);
> +		if (ret < 0)
> +			break;
> +		ret = IIO_VAL_INT;
> +		*val = data;
> +		break;
> +	default:
> +		ret = cros_ec_sensors_core_read(&st->core, chan, val, val2,
> +						mask);
> +		break;
> +	}
> +	mutex_unlock(&st->core.cmd_lock);
> +	return ret;
> +}
> +
> +static struct iio_info cros_ec_sensors_sync_info = {
> +	.read_raw = &cros_ec_sensors_sync_read,
> +	.read_avail = &cros_ec_sensors_core_read_avail,
> +};
> +
> +static struct counter_count cros_ec_sync_counts = {
> +	.id = 0,
> +	.name = "Cros EC sync counter",
> +};
> +
> +static int cros_ec_sync_cnt_read(struct counter_device *counter,
> +				struct counter_count *count,
> +				struct counter_count_read_value *val)
> +{
> +	s16 cnt;
> +	int ret;
> +	struct iio_dev *indio_dev = counter->priv;
> +	struct cros_ec_sensors_sync_state *const st = iio_priv(indio_dev);
> +	unsigned long data;
> +
> +	mutex_lock(&st->core.cmd_lock);
> +	ret = cros_ec_sensors_read_cmd(indio_dev, BIT(0), &cnt);
> +	mutex_unlock(&st->core.cmd_lock);
> +	if (ret != 0) {
> +		dev_warn(&indio_dev->dev, "Unable to read sensor data\n");
> +		return ret;
> +	}
> +
> +	data = (unsigned long) cnt;

This cast is not necessary since the data variable is already unsigned
long; conversion can occur implicitly with a simple set operation.

> +	counter_count_read_value_set(val, COUNTER_COUNT_TALLY, &data);
> +
> +	return 0;
> +}
> +
> +static const struct counter_ops cros_ec_sync_cnt_ops = {
> +	.count_read = cros_ec_sync_cnt_read,
> +};

Like in my previous review: does the hardware allow the counter to be
reset back to zero, or is it purely read-only? It's okay if you want to
focus on just reading for this patch, but it'll be good to know the
capabilities of this hardware if we want support for it in the future.

> +
> +static char *cros_ec_loc[] = {
> +	[MOTIONSENSE_LOC_BASE] = "base",
> +	[MOTIONSENSE_LOC_LID] = "lid",
> +	[MOTIONSENSE_LOC_CAMERA] = "camera",
> +	[MOTIONSENSE_LOC_MAX] = "unknown",
> +};
> +
> +static ssize_t cros_ec_sync_id(struct counter_device *counter,
> +				  void *private, char *buf)
> +{
> +	struct iio_dev *indio_dev = counter->priv;
> +	struct cros_ec_sensors_sync_state *const st = iio_priv(indio_dev);
> +
> +	return snprintf(buf, PAGE_SIZE, "%d\n", st->core.param.info.sensor_num);
> +}
> +
> +static ssize_t cros_ec_sync_loc(struct counter_device *counter,
> +				   void *private, char *buf)
> +{
> +	struct iio_dev *indio_dev = counter->priv;
> +	struct cros_ec_sensors_sync_state *const st = iio_priv(indio_dev);
> +
> +	return snprintf(buf, PAGE_SIZE, "%s\n", cros_ec_loc[st->core.loc]);
> +}
> +
> +static struct counter_device_ext cros_ec_sync_cnt_ext[] = {
> +	{
> +		.name = "id",
> +		.read = cros_ec_sync_id
> +	},
> +	{
> +		.name = "location",
> +		.read = cros_ec_sync_loc
> +	},
> +};

Create a corresponding documentation file to describe these attributes:
Documentation/ABI/testing/sysfs-bus-counter-cros_ec_sensors_sync

> +
> +static int cros_ec_sensors_sync_probe(struct platform_device *pdev)
> +{
> +	struct cros_ec_sensors_sync_state *state;
> +	struct device *dev = &pdev->dev;
> +	struct iio_chan_spec *channel;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*state));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	ret = cros_ec_sensors_core_init(pdev, indio_dev, true);
> +	if (ret)
> +		return ret;
> +
> +	indio_dev->info = &cros_ec_sensors_sync_info;
> +	state = iio_priv(indio_dev);
> +
> +	if (state->core.type != MOTIONSENSE_TYPE_SYNC)
> +		return -EINVAL;
> +
> +	/* Initialize IIO device */
> +	channel = state->channels;
> +	channel->type = IIO_TIMESTAMP;
> +	channel->channel = -1;
> +	channel->scan_index = 1;
> +	channel->scan_type.sign = 's';
> +	channel->scan_type.realbits = 64;
> +	channel->scan_type.storagebits = 64;
> +
> +	indio_dev->channels = state->channels;
> +	indio_dev->num_channels = MAX_CHANNELS;
> +
> +	state->core.read_ec_sensors_data = cros_ec_sensors_read_cmd;
> +
> +	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
> +					      cros_ec_sensors_capture, NULL);
> +	if (ret)
> +		return ret;
> +
> +	ret = devm_iio_device_register(dev, indio_dev);
> +	if (ret)
> +		return ret;
> +
> +	/* Initialize counter device */
> +	state->counter.name = dev_name(&pdev->dev);
> +	state->counter.parent = &pdev->dev;
> +	state->counter.counts = &cros_ec_sync_counts;
> +	state->counter.num_counts = 1;
> +	state->counter.priv = indio_dev;
> +	state->counter.ops = &cros_ec_sync_cnt_ops;
> +	state->counter.ext = cros_ec_sync_cnt_ext;
> +	state->counter.num_ext = ARRAY_SIZE(cros_ec_sync_cnt_ext);
> +
> +	return devm_counter_register(&pdev->dev, &state->counter);
> +}
> +
> +static const struct platform_device_id cros_ec_sensors_sync_ids[] = {
> +	{ .name = DRV_NAME, },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(platform, cros_ec_sensors_sync_ids);
> +
> +static struct platform_driver cros_ec_sensors_sync_platform_driver = {
> +	.driver = {
> +		.name	= DRV_NAME,
> +		.pm	= &cros_ec_sensors_pm_ops,
> +	},
> +	.probe		= cros_ec_sensors_sync_probe,
> +	.id_table	= cros_ec_sensors_sync_ids,
> +};
> +module_platform_driver(cros_ec_sensors_sync_platform_driver);
> +
> +MODULE_DESCRIPTION("ChromeOS EC synchronisation sensor driver");
> +MODULE_ALIAS("platform:" DRV_NAME);
> +MODULE_LICENSE("GPL v2");

From the email you sent in response to Jonathan Cameron's comments, the
IIO code in this driver will be removed so that should take care of the
error message reported by the kbuild test robot. With only the Counter
subsystem to worry about, this driver should end up a lot simpler in v3.
I'm looking forward to it. :-)

William Breathitt Gray

> diff --git a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> index 805652250960..2bf183425eaf 100644
> --- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> +++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> @@ -22,6 +22,7 @@
>  static char *cros_ec_loc[] = {
>  	[MOTIONSENSE_LOC_BASE] = "base",
>  	[MOTIONSENSE_LOC_LID] = "lid",
> +	[MOTIONSENSE_LOC_CAMERA] = "camera",
>  	[MOTIONSENSE_LOC_MAX] = "unknown",
>  };
>  
> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> index 41dccced5026..1c5c2c38af88 100644
> --- a/drivers/mfd/cros_ec_dev.c
> +++ b/drivers/mfd/cros_ec_dev.c
> @@ -332,6 +332,9 @@ static void cros_ec_sensors_register(struct cros_ec_dev *ec)
>  		case MOTIONSENSE_TYPE_ACTIVITY:
>  			sensor_cells[id].name = "cros-ec-activity";
>  			break;
> +		case MOTIONSENSE_TYPE_SYNC:
> +			sensor_cells[id].name = "cros-ec-sync";
> +			break;
>  		default:
>  			dev_warn(ec->dev, "unknown type %d\n", resp->info.type);
>  			continue;
> diff --git a/include/linux/counter.h b/include/linux/counter.h
> index a061cdcdef7c..1198e675306f 100644
> --- a/include/linux/counter.h
> +++ b/include/linux/counter.h
> @@ -488,6 +488,7 @@ enum counter_signal_value_type {
>  
>  enum counter_count_value_type {
>  	COUNTER_COUNT_POSITION = 0,
> +	COUNTER_COUNT_TALLY
>  };
>  
>  void counter_signal_read_value_set(struct counter_signal_read_value *const val,
> -- 
> 2.20.1
>