Re: [PATCH v4 3/4] platform/chrome: Add cros_ec_accel_legacy driver

[Jonathan Cameron]

On Thu, 12 Oct 2017 19:33:23 +0200
Thierry Escande <thierry.escande@xxxxxxxxxxxxx> wrote:

> From: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
> 
> Add driver to support older EC firmware that only support deprecated
> ec command. Rely on ACPI memory map register to access sensor
> information.
> Present same interface as the regular cros_ec sensor stack:
> - one iio device per accelerometer
> - use HTML5 axis definition
> - use iio abi units
> - accept calibration calls, but do nothing
> Chrome can use the same code than regular cros_ec sensor stack to
> calculate orientation and lid angle.
> 
> Signed-off-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
> Signed-off-by: Thierry Escande <thierry.escande@xxxxxxxxxxxxx>

There is going to be a merge conflict over the removal of
.driver_module from struct iio_info.  Solution is delete that
entry - but this may not be entirely obvious to who ever has to
deal with that.  Hence I've taken one patch through iio.git.

One trivial formatting point inline I also tidied up.

I 'think' there should be nothing stopping me taking this patch
via iio whilst the others go a different route...

Applied to the togreg branch of iio.git and pushed out as testing for the
autobuilders to play with it.

I've tweaked u16 tmp to le16 tmp to fix up a sparse warning. 

Please check I haven't mess it up.

Jonathan

> ---
>  Documentation/ABI/testing/sysfs-bus-iio-cros-ec |  10 +
>  drivers/iio/accel/Kconfig                       |  11 +
>  drivers/iio/accel/Makefile                      |   2 +
>  drivers/iio/accel/cros_ec_accel_legacy.c        | 425 ++++++++++++++++++++++++
>  4 files changed, 448 insertions(+)
>  create mode 100644 drivers/iio/accel/cros_ec_accel_legacy.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-cros-ec b/Documentation/ABI/testing/sysfs-bus-iio-cros-ec
> index 297b972..0e95c2c 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio-cros-ec
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-cros-ec
> @@ -16,3 +16,13 @@ Description:
>                  the motion sensor is placed. For example, in a laptop a motion
>                  sensor can be located on the base or on the lid. Current valid
>  		values are 'base' and 'lid'.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/id
> +Date:		Septembre 2017
> +KernelVersion:	4.14
> +Contact:	linux-iio@xxxxxxxxxxxxxxx
> +Description:
> +		This attribute is exposed by the CrOS EC legacy accelerometer
> +		driver and represents the sensor ID as exposed by the EC. This
> +		ID is used by the Android sensor service hardware abstraction
> +		layer (sensor HAL) through the Android container on ChromeOS.
> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> index 15de262..5a1ef29 100644
> --- a/drivers/iio/accel/Kconfig
> +++ b/drivers/iio/accel/Kconfig
> @@ -148,6 +148,17 @@ config HID_SENSOR_ACCEL_3D
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called hid-sensor-accel-3d.
>  
> +config IIO_CROS_EC_ACCEL_LEGACY
> +	tristate "ChromeOS EC Legacy Accelerometer Sensor"
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
> +	select CROS_EC_LPC_REGISTER_DEVICE
> +	help
> +	  Say yes here to get support for accelerometers on Chromebook using
> +	  legacy EC firmware.
> +	  Sensor data is retrieved through IO memory.
> +	  Newer devices should use IIO_CROS_EC_SENSORS.
> +
>  config IIO_ST_ACCEL_3AXIS
>  	tristate "STMicroelectronics accelerometers 3-Axis Driver"
>  	depends on (I2C || SPI_MASTER) && SYSFS
> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
> index 31fba19..fdd054a 100644
> --- a/drivers/iio/accel/Makefile
> +++ b/drivers/iio/accel/Makefile
> @@ -43,6 +43,8 @@ obj-$(CONFIG_SCA3000)		+= sca3000.o
>  obj-$(CONFIG_STK8312)		+= stk8312.o
>  obj-$(CONFIG_STK8BA50)		+= stk8ba50.o
>  
> +obj-$(CONFIG_IIO_CROS_EC_ACCEL_LEGACY) += cros_ec_accel_legacy.o
> +
>  obj-$(CONFIG_IIO_SSP_SENSORS_COMMONS) += ssp_accel_sensor.o
>  
>  obj-$(CONFIG_IIO_ST_ACCEL_3AXIS) += st_accel.o
> diff --git a/drivers/iio/accel/cros_ec_accel_legacy.c b/drivers/iio/accel/cros_ec_accel_legacy.c
> new file mode 100644
> index 0000000..be13f2a
> --- /dev/null
> +++ b/drivers/iio/accel/cros_ec_accel_legacy.c
> @@ -0,0 +1,425 @@
> +/*
> + * Driver for older Chrome OS EC accelerometer
> + *
> + * Copyright 2017 Google, Inc
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * This driver uses the memory mapper cros-ec interface to communicate
> + * with the Chrome OS EC about accelerometer data.
> + * Accelerometer access is presented through iio sysfs.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/kfifo_buf.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/cros_ec.h>
> +#include <linux/mfd/cros_ec_commands.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>
> +#include <linux/platform_device.h>
> +
> +#define DRV_NAME	"cros-ec-accel-legacy"
> +
> +/*
> + * Sensor scale hard coded at 10 bits per g, computed as:
> + * g / (2^10 - 1) = 0.009586168; with g = 9.80665 m.s^-2
> + */
> +#define ACCEL_LEGACY_NSCALE 9586168
> +
> +/* Indices for EC sensor values. */
> +enum {
> +	X,
> +	Y,
> +	Z,
> +	MAX_AXIS,
> +};
> +
> +/* State data for cros_ec_accel_legacy iio driver. */
> +struct cros_ec_accel_legacy_state {
> +	struct cros_ec_device *ec;
> +
> +	/*
> +	 * Array holding data from a single capture. 2 bytes per channel
> +	 * for the 3 channels plus the timestamp which is always last and
> +	 * 8-bytes aligned.
> +	 */
> +	s16 capture_data[8];
> +	s8 sign[MAX_AXIS];
> +	u8 sensor_num;
> +};
> +
> +static int ec_cmd_read_u8(struct cros_ec_device *ec, unsigned int offset,
> +			  u8 *dest)
> +{
> +	return ec->cmd_readmem(ec, offset, 1, dest);
> +}
> +
> +static int ec_cmd_read_u16(struct cros_ec_device *ec, unsigned int offset,
> +			   u16 *dest)
> +{
> +	u16 tmp;
> +	int ret = ec->cmd_readmem(ec, offset, 2, &tmp);
> +
> +	*dest = le16_to_cpu(tmp);
> +
> +	return ret;
> +}
> +
> +/**
> + * read_ec_until_not_busy() - Read from EC status byte until it reads not busy.
> + * @st: Pointer to state information for device.
> + *
> + * This function reads EC status until its busy bit gets cleared. It does not
> + * wait indefinitely and returns -EIO if the EC status is still busy after a
> + * few hundreds milliseconds.
> + *
> + * Return: 8-bit status if ok, -EIO on error
> + */
> +static int read_ec_until_not_busy(struct cros_ec_accel_legacy_state *st)
> +{
> +	struct cros_ec_device *ec = st->ec;
> +	u8 status;
> +	int attempts = 0;
> +
> +	ec_cmd_read_u8(ec, EC_MEMMAP_ACC_STATUS, &status);
> +	while (status & EC_MEMMAP_ACC_STATUS_BUSY_BIT) {
> +		/* Give up after enough attempts, return error. */
> +		if (attempts++ >= 50)
> +			return -EIO;
> +
> +		/* Small delay every so often. */
> +		if (attempts % 5 == 0)
> +			msleep(25);
> +
> +		ec_cmd_read_u8(ec, EC_MEMMAP_ACC_STATUS, &status);
> +	}
> +
> +	return status;
> +}
> +
> +/**
> + * read_ec_accel_data_unsafe() - Read acceleration data from EC shared memory.
> + * @st:        Pointer to state information for device.
> + * @scan_mask: Bitmap of the sensor indices to scan.
> + * @data:      Location to store data.
> + *
> + * This is the unsafe function for reading the EC data. It does not guarantee
> + * that the EC will not modify the data as it is being read in.
> + */
> +static void read_ec_accel_data_unsafe(struct cros_ec_accel_legacy_state *st,
> +				      unsigned long scan_mask, s16 *data)
> +{
> +	int i = 0;
> +	int num_enabled = bitmap_weight(&scan_mask, MAX_AXIS);
> +
> +	/* Read all sensors enabled in scan_mask. Each value is 2 bytes. */
> +	while (num_enabled--) {
> +		i = find_next_bit(&scan_mask, MAX_AXIS, i);
> +		ec_cmd_read_u16(
> +			st->ec,
> +			EC_MEMMAP_ACC_DATA +
> +				sizeof(s16) *
> +				(1 + i + st->sensor_num * MAX_AXIS),        
> +			data);
Really small point, but i don't think there is any need for this odd bit of indention.

		ec_cmd_read_u16(st->ec,
				EC_MEMMAP_ACC_DATA +
				sizeof(s16) *
				(1 + i + st->sensor_num * MAX_AXIS),
				data);

> +		*data *= st->sign[i];
> +		i++;
> +		data++;
> +	}
> +}
> +
> +/**
> + * read_ec_accel_data() - Read acceleration data from EC shared memory.
> + * @st:        Pointer to state information for device.
> + * @scan_mask: Bitmap of the sensor indices to scan.
> + * @data:      Location to store data.
> + *
> + * This is the safe function for reading the EC data. It guarantees that
> + * the data sampled was not modified by the EC while being read.
> + *
> + * Return: 0 if ok, -ve on error
> + */
> +static int read_ec_accel_data(struct cros_ec_accel_legacy_state *st,
> +			      unsigned long scan_mask, s16 *data)
> +{
> +	u8 samp_id = 0xff;
> +	u8 status = 0;
> +	int ret;
> +	int attempts = 0;
> +
> +	/*
> +	 * Continually read all data from EC until the status byte after
> +	 * all reads reflects that the EC is not busy and the sample id
> +	 * matches the sample id from before all reads. This guarantees
> +	 * that data read in was not modified by the EC while reading.
> +	 */
> +	while ((status & (EC_MEMMAP_ACC_STATUS_BUSY_BIT |
> +			  EC_MEMMAP_ACC_STATUS_SAMPLE_ID_MASK)) != samp_id) {
> +		/* If we have tried to read too many times, return error. */
> +		if (attempts++ >= 5)
> +			return -EIO;
> +
> +		/* Read status byte until EC is not busy. */
> +		ret = read_ec_until_not_busy(st);
> +		if (ret < 0)
> +			return ret;
> +		status = ret;
> +
> +		/*
> +		 * Store the current sample id so that we can compare to the
> +		 * sample id after reading the data.
> +		 */
> +		samp_id = status & EC_MEMMAP_ACC_STATUS_SAMPLE_ID_MASK;
> +
> +		/* Read all EC data, format it, and store it into data. */
> +		read_ec_accel_data_unsafe(st, scan_mask, data);
> +
> +		/* Read status byte. */
> +		ec_cmd_read_u8(st->ec, EC_MEMMAP_ACC_STATUS, &status);
> +	}
> +
> +	return 0;
> +}
> +
> +static int cros_ec_accel_legacy_read(struct iio_dev *indio_dev,
> +				     struct iio_chan_spec const *chan,
> +				     int *val, int *val2, long mask)
> +{
> +	struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
> +	s16 data = 0;
> +	int ret = IIO_VAL_INT;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = read_ec_accel_data(st, (1 << chan->scan_index), &data);
> +		if (ret)
> +			return ret;
> +		*val = data;
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = 0;
> +		*val2 = ACCEL_LEGACY_NSCALE;
> +		return IIO_VAL_INT_PLUS_NANO;
> +	case IIO_CHAN_INFO_CALIBBIAS:
> +		/* Calibration not supported. */
> +		*val = 0;
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int cros_ec_accel_legacy_write(struct iio_dev *indio_dev,
> +				      struct iio_chan_spec const *chan,
> +				      int val, int val2, long mask)
> +{
> +	/*
> +	 * Do nothing but don't return an error code to allow calibration
> +	 * script to work.
> +	 */
> +	if (mask == IIO_CHAN_INFO_CALIBBIAS)
> +		return 0;
> +
> +	return -EINVAL;
> +}
> +
> +static const struct iio_info cros_ec_accel_legacy_info = {
> +	.read_raw = &cros_ec_accel_legacy_read,
> +	.write_raw = &cros_ec_accel_legacy_write,
> +	.driver_module = THIS_MODULE,

driver_module is gone from the iio tree now which is going to give us a
merge conflict if this goes through a non IIO tree.

> +};
> +
> +/**
> + * cros_ec_accel_legacy_capture() - The trigger handler function
> + * @irq: The interrupt number.
> + * @p:   Private data - always a pointer to the poll func.
> + *
> + * On a trigger event occurring, if the pollfunc is attached then this
> + * handler is called as a threaded interrupt (and hence may sleep). It
> + * is responsible for grabbing data from the device and pushing it into
> + * the associated buffer.
> + *
> + * Return: IRQ_HANDLED
> + */
> +static irqreturn_t cros_ec_accel_legacy_capture(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
> +
> +	/* Clear capture data. */
> +	memset(st->capture_data, 0, sizeof(st->capture_data));
> +
> +	/*
> +	 * Read data based on which channels are enabled in scan mask. Note
> +	 * that on a capture we are always reading the calibrated data.
> +	 */
> +	read_ec_accel_data(st, *indio_dev->active_scan_mask, st->capture_data);
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, (void *)st->capture_data,
> +					   iio_get_time_ns(indio_dev));
> +
> +	/*
> +	 * Tell the core we are done with this trigger and ready for the
> +	 * next one.
> +	 */
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static char *cros_ec_accel_legacy_loc_strings[] = {
> +	[MOTIONSENSE_LOC_BASE] = "base",
> +	[MOTIONSENSE_LOC_LID] = "lid",
> +	[MOTIONSENSE_LOC_MAX] = "unknown",
> +};
> +
> +static ssize_t cros_ec_accel_legacy_loc(struct iio_dev *indio_dev,
> +					uintptr_t private,
> +					const struct iio_chan_spec *chan,
> +					char *buf)
> +{
> +	struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%s\n",
> +		       cros_ec_accel_legacy_loc_strings[st->sensor_num +
> +							MOTIONSENSE_LOC_BASE]);
> +}
> +
> +static ssize_t cros_ec_accel_legacy_id(struct iio_dev *indio_dev,
> +				       uintptr_t private,
> +				       const struct iio_chan_spec *chan,
> +				       char *buf)
> +{
> +	struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%d\n", st->sensor_num);
> +}
> +
> +static const struct iio_chan_spec_ext_info cros_ec_accel_legacy_ext_info[] = {
> +	{
> +		.name = "id",
> +		.shared = IIO_SHARED_BY_ALL,
> +		.read = cros_ec_accel_legacy_id,
> +	},
> +	{
> +		.name = "location",
> +		.shared = IIO_SHARED_BY_ALL,
> +		.read = cros_ec_accel_legacy_loc,
> +	},
> +	{ }
> +};
> +
> +#define CROS_EC_ACCEL_LEGACY_CHAN(_axis)				\
> +	{								\
> +		.type = IIO_ACCEL,					\
> +		.channel2 = IIO_MOD_X + (_axis),			\
> +		.modified = 1,					        \
> +		.info_mask_separate =					\
> +			BIT(IIO_CHAN_INFO_RAW) |			\
> +			BIT(IIO_CHAN_INFO_SCALE) |			\
> +			BIT(IIO_CHAN_INFO_CALIBBIAS),			\
> +		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE),	\
> +		.ext_info = cros_ec_accel_legacy_ext_info,		\
> +		.scan_type = {						\
> +			.sign = 's',					\
> +			.realbits = 16,					\
> +			.storagebits = 16,				\
> +		},							\
> +	}								\
> +
> +static struct iio_chan_spec ec_accel_channels[] = {
> +	CROS_EC_ACCEL_LEGACY_CHAN(X),
> +	CROS_EC_ACCEL_LEGACY_CHAN(Y),
> +	CROS_EC_ACCEL_LEGACY_CHAN(Z),
> +	IIO_CHAN_SOFT_TIMESTAMP(MAX_AXIS)
> +};
> +
> +static int cros_ec_accel_legacy_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct cros_ec_dev *ec = dev_get_drvdata(dev->parent);
> +	struct cros_ec_sensor_platform *sensor_platform = dev_get_platdata(dev);
> +	struct iio_dev *indio_dev;
> +	struct cros_ec_accel_legacy_state *state;
> +	int ret, i;
> +
> +	if (!ec || !ec->ec_dev) {
> +		dev_warn(&pdev->dev, "No EC device found.\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!ec->ec_dev->cmd_readmem) {
> +		dev_warn(&pdev->dev, "EC does not support direct reads.\n");
> +		return -EINVAL;
> +	}
> +
> +	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*state));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, indio_dev);
> +	state = iio_priv(indio_dev);
> +	state->ec = ec->ec_dev;
> +	state->sensor_num = sensor_platform->sensor_num;
> +
> +	indio_dev->dev.parent = dev;
> +	indio_dev->name = pdev->name;
> +	indio_dev->channels = ec_accel_channels;
> +	/*
> +	 * Present the channel using HTML5 standard:
> +	 * need to invert X and Y and invert some lid axis.
> +	 */
> +	for (i = X ; i < MAX_AXIS; i++) {
> +		switch (i) {
> +		case X:
> +			ec_accel_channels[X].scan_index = Y;
> +		case Y:
> +			ec_accel_channels[Y].scan_index = X;
> +		case Z:
> +			ec_accel_channels[Z].scan_index = Z;
> +		}
> +		if (state->sensor_num == MOTIONSENSE_LOC_LID && i != Y)
> +			state->sign[i] = -1;
> +		else
> +			state->sign[i] = 1;
> +	}
> +	indio_dev->num_channels = ARRAY_SIZE(ec_accel_channels);
> +	indio_dev->dev.parent = &pdev->dev;
> +	indio_dev->info = &cros_ec_accel_legacy_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
> +					      cros_ec_accel_legacy_capture,
> +					      NULL);
> +	if (ret)
> +		return ret;
> +
> +	return devm_iio_device_register(dev, indio_dev);
> +}
> +
> +static struct platform_driver cros_ec_accel_platform_driver = {
> +	.driver = {
> +		.name	= DRV_NAME,
> +	},
> +	.probe		= cros_ec_accel_legacy_probe,
> +};
> +module_platform_driver(cros_ec_accel_platform_driver);
> +
> +MODULE_DESCRIPTION("ChromeOS EC legacy accelerometer driver");
> +MODULE_AUTHOR("Gwendal Grignou <gwendal@xxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:" DRV_NAME);