iio: cros_ec: Allow enabling/disabling calibration mode

'calibrate' was a one-shot event sent to the sensor to calibrate itself.
It is used on Bosch sensors (BMI160, BMA254).
Light sensors work differently: They are first put in calibration mode,
tests are run to collect information and calculate the calibration
values to apply. Once done, the sensors are put back in normal mode.

Accept boolean true and false (not just true) to enter/exit calibration
state.

Check "echo 0 > calibrate" is supported.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: gwendalcr

Documentation/ABI/testing/sysfs-bus-iio-cros-ec

@@ -3,9 +3,12 @@ Date:		July 2015
 KernelVersion:	4.7
 Contact:	linux-iio@vger.kernel.org
 Description:
-		Writing '1' will perform a FOC (Fast Online Calibration). The
-                corresponding calibration offsets can be read from `*_calibbias`
-                entries.
+		Writing '1' either perform a FOC (Fast Online Calibration) or
+		enter calibration mode.
+		Writing '0` exits calibration mode. It is a NOP for FOC enabled
+		sensors.
+		The corresponding calibration offsets can be read from `*_calibbias`
+		entries.
 
 What:		/sys/bus/iio/devices/iio:deviceX/id
 Date:		September 2017

drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c

@@ -441,14 +441,14 @@ static ssize_t cros_ec_sensors_calibrate(struct iio_dev *indio_dev,
 	ret = kstrtobool(buf, &calibrate);
 	if (ret < 0)
 		return ret;
-	if (!calibrate)
-		return -EINVAL;
 
 	mutex_lock(&st->cmd_lock);
 	st->param.cmd = MOTIONSENSE_CMD_PERFORM_CALIB;
+	st->param.perform_calib.enable = calibrate;
 	ret = cros_ec_motion_send_host_cmd(st, 0);
 	if (ret != 0) {
-		dev_warn(&indio_dev->dev, "Unable to calibrate sensor\n");
+		dev_warn(&indio_dev->dev, "Unable to calibrate sensor: %d\n",
+			 ret);
 	} else {
 		/* Save values */
 		for (i = CROS_EC_SENSOR_X; i < CROS_EC_SENSOR_MAX_AXIS; i++)

include/linux/platform_data/cros_ec_commands.h

@@ -2598,13 +2598,19 @@ struct ec_params_motion_sense {
 
 		/*
 		 * Used for MOTIONSENSE_CMD_INFO, MOTIONSENSE_CMD_DATA
-		 * and MOTIONSENSE_CMD_PERFORM_CALIB.
 		 */
 		struct __ec_todo_unpacked {
 			uint8_t sensor_num;
-		} info, info_3, data, fifo_flush, perform_calib,
-				list_activities;
+		} info, info_3, data, fifo_flush, list_activities;
 
+		/*
+		 * Used for MOTIONSENSE_CMD_PERFORM_CALIB:
+		 * Allow entering/exiting the calibration mode.
+		 */
+		struct __ec_todo_unpacked {
+			uint8_t sensor_num;
+			uint8_t enable;
+		} perform_calib;
 		/*
 		 * Used for MOTIONSENSE_CMD_EC_RATE, MOTIONSENSE_CMD_SENSOR_ODR
 		 * and MOTIONSENSE_CMD_SENSOR_RANGE.