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Message-ID: <8abbe9360938ab851d16c2c1494ba56034775823.camel@collabora.com>
Subject: Re: [PATCH v2 1/1] counter: cros_ec: Add synchronization sensor
From:   Fabien Lahoudere <fabien.lahoudere@collabora.com>
To:     Jonathan Cameron <jic23@kernel.org>
Cc:     gwendal@chromium.org, egranata@chromium.org, kernel@collabora.com,
        William Breathitt Gray <vilhelm.gray@gmail.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Guenter Roeck <groeck@chromium.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
Date:   Thu, 29 Aug 2019 13:10:41 +0200
In-Reply-To: <20190826095612.7455cb05@archlinux>
References: <cover.1566563833.git.fabien.lahoudere@collabora.com>
         <d985a8a811996148e8cda78b9fe47bb87b884b56.1566563833.git.fabien.lahoudere@collabora.com>
         <20190826095612.7455cb05@archlinux>
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Le lundi 26 août 2019 à 09:56 +0100, Jonathan Cameron a écrit :
> On Fri, 23 Aug 2019 14:41:27 +0200
> Fabien Lahoudere <fabien.lahoudere@collabora.com> 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.
> 
> I'm curious.  What is this counter used for?

It is a counter of a pin connected to a camera vsync.
It is used to manage correct orientation of the camera when the
gyroscope detect a change.

> 
> This combined counter and iio driver isn't something we would
> normally
> want to support.  What is the reasoning behind doing both interfaces?

That patch was originally designed using only IIO with IIO_count and
IIO_TIMESTAMP channel. As IIO_COUNT is deprecated, we need to use the
new counter subsystem. So I just split the driver in two part counter
and iio timestamp.

However after your email I did some investigation and did not find any
use of the timestamp for that sensor. Timestamp is just a common
channel implemented on all CROS EC sensors.

So I think I will drop it now and if a timestamp is needed, I will
probably restart the discussion about timestamp in the counter
subsystemif that make sense to have one.

Thanks

Fabien

> 
> > 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>
> > +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;
> > 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;
> > +	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,
> > +};
> > +
> > +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
> > +	},
> > +};
> > +
> > +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);
> 
> Hmm. Wasn't expecting to see that here if it's a counter device.
> 
> 
> > +	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");
> > 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,