Re: [PATCH 1/2 v7] iio: st_sensors: switch to a threaded interrupt

[Jonathan Cameron <jic23@kernel.org>]

On 22/05/16 20:59, Jonathan Cameron wrote:
> On 21/05/16 19:43, Linus Walleij wrote:
>> commit 98ad8b41f58dff6b30713d7f09ae3834b8df7ded
>> ("iio: st_sensors: verify interrupt event to status") caused
>> a regression when reading ST sensors from a HRTimer trigger
>> rather than the intrinsic interrupts: the HRTimer may
>> trigger faster than the sensor provides new values, and
>> as the check against new values available as a cause of
>> the interrupt trigger was done in the poll function,
>> this would bail out of the HRTimer interrupt with
>> IRQ_NONE.
>>
>> So clearly we need to only check the new values available
>> from the proper interrupt handler and not from the poll
>> function, which should rather just read the raw values
>> from the registers, put them into the buffer and be happy.
>>
>> To achieve this: switch the ST Sensors over to using a true
>> threaded interrupt handler.
>>
>> In the interrupt thread, check if new values are available,
>> else yield to the (potential) next device on the same
>> interrupt line to check the registers. If the interrupt
>> was ours, proceed to poll the values.
>>
>> Instead of relying on iio_trigger_generic_data_rdy_poll() as
>> a top half to wake up the thread that polls the sensor for
>> new data, have the thread call iio_trigger_poll_chained()
>> after determining that is is the proper source of the
>> interrupt. This is modelled on drivers/iio/accel/mma8452.c
>> which is already using a properly threaded interrupt handler.
>>
>> In order to get the same precision in timestamps as
>> previously, where samples would be timestamped in the
>> poll function pf->timestamp when calling
>> iio_trigger_generic_data_rdy_poll() we introduce a
>> local timestamp in the sensor data, set it in the top half
>> (fastpath) of the interrupt handler and provide that to the
>> core when calling iio_push_to_buffers_with_timestamp().
>>
>> Additionally: if the active scanmask is not set for the
>> sensor no IRQs should be enabled and we need to bail out
>> with IRQ_NONE. This can happen if spurious IRQs fire when
>> installing the threaded interrupt handler.
>>
>> Tested with hard interrupt triggers on LIS331DL, then also
>> tested with hrtimers on the same sensor by creating a 75Hz
>> HRTimer and using it to poll the sensor.
>>
>> Cc: Giuseppe Barba <giuseppe.barba@st.com>
>> Cc: Denis Ciocca <denis.ciocca@st.com>
>> Reported-by: Crestez Dan Leonard <cdleonard@gmail.com>
>> Tested-by: Crestez Dan Leonard <cdleonard@gmail.com>
>> Fixes: 97865fe41322 ("iio: st_sensors: verify interrupt event to status")
>> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> I've tested this as well now.  Will let it sit for a few more days
> as it won't make any difference until rc1 is out and may give
> Denis / Giuseppe a chance to check it as well.
Applied to the fixes-togreg-post-rc1 branch of iio.git.

Thanks,

Jonathan
> 
> Works nicely.
> 
> Jonathan
>> ---
>> ChangeLog v6->v7:
>> - Cut the higher bits of the status word explicitly and do not
>>   assume it to be masked by the .active_scan_mask[0].
>> - NOTE: this patch is a regression fix and can be applied
>>   without 2/2. Hopefully this can go into v4.7-rc:s now.
>> ChangeLog v5->v6:
>> - Set the triggered buffer top half IRQ handler to NULL in all
>>   subdrivers (accelerometer, gyro, magnetometer, pressure) as
>>   we now use the iio_trigger_poll_chained() call.
>> - Add st_sensors_validate_device() to the intrinsic triggers
>>   and set as .validate_deice() for all subdrivers. Its purpose
>>   is to check that the trigger is indeed provided by this
>>   device before we use it.
>> ChangeLog v4->v5:
>> - Move the setting of hw_irq_enabled to before the register
>>   write to enable interrupts so we avoid a race where this
>>   variable could be read in its previous state.
>> ChangeLog v3->v4:
>> - v3 would not timestamp properly when using a HRTimer to read
>>   values from the sensors. This is now fixed.
>> - Add a flag to the sensor data indicating whether the hardware
>>   interrupt trigger is in use. If this is the case, we use that
>>   timestamp. If the hardware trigger is not in use, we just let
>>   the poll function read the current time before proceeding to
>>   grab the values from the sensor.
>> - Move interrupt top/bottom halves to st_sensors_trigger.c so the
>>   interrupt code is kept together and easier to understand in
>>   context.
>> ChangeLog v2->v3:
>> - v2 was a total disaster, as iio_trigger_generic_data_rdy_poll()
>>   would just call the old bottom half and return IRQ_HANDLED.
>>   handle the timestamp locally in the sensor data and restore
>>   the usage of the local interrupt thread.
>> - I think it works now.
>> ChangeLog v1->v2:
>> - v1 was missing timestamps since nothing ever stamped them.
>>   Restore the timestamps by simply using
>>   iio_trigger_generic_data_rdy_poll()
>>   as the top half of the threaded interrupt handler.
>> ---
>>  drivers/iio/accel/st_accel_buffer.c                |  2 +-
>>  drivers/iio/accel/st_accel_core.c                  |  1 +
>>  drivers/iio/common/st_sensors/st_sensors_buffer.c  | 25 ++----
>>  drivers/iio/common/st_sensors/st_sensors_core.c    |  3 +
>>  drivers/iio/common/st_sensors/st_sensors_trigger.c | 88 +++++++++++++++++++++-
>>  drivers/iio/gyro/st_gyro_buffer.c                  |  2 +-
>>  drivers/iio/gyro/st_gyro_core.c                    |  1 +
>>  drivers/iio/magnetometer/st_magn_buffer.c          |  2 +-
>>  drivers/iio/magnetometer/st_magn_core.c            |  1 +
>>  drivers/iio/pressure/st_pressure_buffer.c          |  2 +-
>>  drivers/iio/pressure/st_pressure_core.c            |  1 +
>>  include/linux/iio/common/st_sensors.h              |  9 ++-
>>  12 files changed, 111 insertions(+), 26 deletions(-)
>>
>> diff --git a/drivers/iio/accel/st_accel_buffer.c b/drivers/iio/accel/st_accel_buffer.c
>> index a1e642ee13d6..7fddc137e91e 100644
>> --- a/drivers/iio/accel/st_accel_buffer.c
>> +++ b/drivers/iio/accel/st_accel_buffer.c
>> @@ -91,7 +91,7 @@ static const struct iio_buffer_setup_ops st_accel_buffer_setup_ops = {
>>  
>>  int st_accel_allocate_ring(struct iio_dev *indio_dev)
>>  {
>> -	return iio_triggered_buffer_setup(indio_dev, &iio_pollfunc_store_time,
>> +	return iio_triggered_buffer_setup(indio_dev, NULL,
>>  		&st_sensors_trigger_handler, &st_accel_buffer_setup_ops);
>>  }
>>  
>> diff --git a/drivers/iio/accel/st_accel_core.c b/drivers/iio/accel/st_accel_core.c
>> index f06f4329db5b..1d9291116556 100644
>> --- a/drivers/iio/accel/st_accel_core.c
>> +++ b/drivers/iio/accel/st_accel_core.c
>> @@ -649,6 +649,7 @@ static const struct iio_info accel_info = {
>>  static const struct iio_trigger_ops st_accel_trigger_ops = {
>>  	.owner = THIS_MODULE,
>>  	.set_trigger_state = ST_ACCEL_TRIGGER_SET_STATE,
>> +	.validate_device = st_sensors_validate_device,
>>  };
>>  #define ST_ACCEL_TRIGGER_OPS (&st_accel_trigger_ops)
>>  #else
>> diff --git a/drivers/iio/common/st_sensors/st_sensors_buffer.c b/drivers/iio/common/st_sensors/st_sensors_buffer.c
>> index c55898543a47..f1693dbebb8a 100644
>> --- a/drivers/iio/common/st_sensors/st_sensors_buffer.c
>> +++ b/drivers/iio/common/st_sensors/st_sensors_buffer.c
>> @@ -57,31 +57,20 @@ irqreturn_t st_sensors_trigger_handler(int irq, void *p)
>>  	struct iio_poll_func *pf = p;
>>  	struct iio_dev *indio_dev = pf->indio_dev;
>>  	struct st_sensor_data *sdata = iio_priv(indio_dev);
>> +	s64 timestamp;
>>  
>> -	/* If we have a status register, check if this IRQ came from us */
>> -	if (sdata->sensor_settings->drdy_irq.addr_stat_drdy) {
>> -		u8 status;
>> -
>> -		len = sdata->tf->read_byte(&sdata->tb, sdata->dev,
>> -			   sdata->sensor_settings->drdy_irq.addr_stat_drdy,
>> -			   &status);
>> -		if (len < 0)
>> -			dev_err(sdata->dev, "could not read channel status\n");
>> -
>> -		/*
>> -		 * If this was not caused by any channels on this sensor,
>> -		 * return IRQ_NONE
>> -		 */
>> -		if (!(status & (u8)indio_dev->active_scan_mask[0]))
>> -			return IRQ_NONE;
>> -	}
>> +	/* If we do timetamping here, do it before reading the values */
>> +	if (sdata->hw_irq_trigger)
>> +		timestamp = sdata->hw_timestamp;
>> +	else
>> +		timestamp = iio_get_time_ns();
>>  
>>  	len = st_sensors_get_buffer_element(indio_dev, sdata->buffer_data);
>>  	if (len < 0)
>>  		goto st_sensors_get_buffer_element_error;
>>  
>>  	iio_push_to_buffers_with_timestamp(indio_dev, sdata->buffer_data,
>> -		pf->timestamp);
>> +					   timestamp);
>>  
>>  st_sensors_get_buffer_element_error:
>>  	iio_trigger_notify_done(indio_dev->trig);
>> diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c
>> index dffe00692169..928ee68fcc5f 100644
>> --- a/drivers/iio/common/st_sensors/st_sensors_core.c
>> +++ b/drivers/iio/common/st_sensors/st_sensors_core.c
>> @@ -424,6 +424,9 @@ int st_sensors_set_dataready_irq(struct iio_dev *indio_dev, bool enable)
>>  	else
>>  		drdy_mask = sdata->sensor_settings->drdy_irq.mask_int2;
>>  
>> +	/* Flag to the poll function that the hardware trigger is in use */
>> +	sdata->hw_irq_trigger = enable;
>> +
>>  	/* Enable/Disable the interrupt generator for data ready. */
>>  	err = st_sensors_write_data_with_mask(indio_dev,
>>  					sdata->sensor_settings->drdy_irq.addr,
>> diff --git a/drivers/iio/common/st_sensors/st_sensors_trigger.c b/drivers/iio/common/st_sensors/st_sensors_trigger.c
>> index da72279fcf99..1f59bcc0f143 100644
>> --- a/drivers/iio/common/st_sensors/st_sensors_trigger.c
>> +++ b/drivers/iio/common/st_sensors/st_sensors_trigger.c
>> @@ -17,6 +17,73 @@
>>  #include <linux/iio/common/st_sensors.h>
>>  #include "st_sensors_core.h"
>>  
>> +/**
>> + * st_sensors_irq_handler() - top half of the IRQ-based triggers
>> + * @irq: irq number
>> + * @p: private handler data
>> + */
>> +irqreturn_t st_sensors_irq_handler(int irq, void *p)
>> +{
>> +	struct iio_trigger *trig = p;
>> +	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
>> +	struct st_sensor_data *sdata = iio_priv(indio_dev);
>> +
>> +	/* Get the time stamp as close in time as possible */
>> +	sdata->hw_timestamp = iio_get_time_ns();
>> +	return IRQ_WAKE_THREAD;
>> +}
>> +
>> +/**
>> + * st_sensors_irq_thread() - bottom half of the IRQ-based triggers
>> + * @irq: irq number
>> + * @p: private handler data
>> + */
>> +irqreturn_t st_sensors_irq_thread(int irq, void *p)
>> +{
>> +	struct iio_trigger *trig = p;
>> +	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
>> +	struct st_sensor_data *sdata = iio_priv(indio_dev);
>> +	int ret;
>> +
>> +	/*
>> +	 * If this trigger is backed by a hardware interrupt and we have a
>> +	 * status register, check if this IRQ came from us
>> +	 */
>> +	if (sdata->sensor_settings->drdy_irq.addr_stat_drdy) {
>> +		u8 status;
>> +
>> +		ret = sdata->tf->read_byte(&sdata->tb, sdata->dev,
>> +			   sdata->sensor_settings->drdy_irq.addr_stat_drdy,
>> +			   &status);
>> +		if (ret < 0) {
>> +			dev_err(sdata->dev, "could not read channel status\n");
>> +			goto out_poll;
>> +		}
>> +		/*
>> +		 * the lower bits of .active_scan_mask[0] is directly mapped
>> +		 * to the channels on the sensor: either bit 0 for
>> +		 * one-dimensional sensors, or e.g. x,y,z for accelerometers,
>> +		 * gyroscopes or magnetometers. No sensor use more than 3
>> +		 * channels, so cut the other status bits here.
>> +		 */
>> +		status &= 0x07;
>> +
>> +		/*
>> +		 * If this was not caused by any channels on this sensor,
>> +		 * return IRQ_NONE
>> +		 */
>> +		if (!indio_dev->active_scan_mask)
>> +			return IRQ_NONE;
>> +		if (!(status & (u8)indio_dev->active_scan_mask[0]))
>> +			return IRQ_NONE;
>> +	}
>> +
>> +out_poll:
>> +	/* It's our IRQ: proceed to handle the register polling */
>> +	iio_trigger_poll_chained(p);
>> +	return IRQ_HANDLED;
>> +}
>> +
>>  int st_sensors_allocate_trigger(struct iio_dev *indio_dev,
>>  				const struct iio_trigger_ops *trigger_ops)
>>  {
>> @@ -77,9 +144,12 @@ int st_sensors_allocate_trigger(struct iio_dev *indio_dev,
>>  	    sdata->sensor_settings->drdy_irq.addr_stat_drdy)
>>  		irq_trig |= IRQF_SHARED;
>>  
>> -	err = request_threaded_irq(irq,
>> -			iio_trigger_generic_data_rdy_poll,
>> -			NULL,
>> +	/* Let's create an interrupt thread masking the hard IRQ here */
>> +	irq_trig |= IRQF_ONESHOT;
>> +
>> +	err = request_threaded_irq(sdata->get_irq_data_ready(indio_dev),
>> +			st_sensors_irq_handler,
>> +			st_sensors_irq_thread,
>>  			irq_trig,
>>  			sdata->trig->name,
>>  			sdata->trig);
>> @@ -119,6 +189,18 @@ void st_sensors_deallocate_trigger(struct iio_dev *indio_dev)
>>  }
>>  EXPORT_SYMBOL(st_sensors_deallocate_trigger);
>>  
>> +int st_sensors_validate_device(struct iio_trigger *trig,
>> +			       struct iio_dev *indio_dev)
>> +{
>> +	struct iio_dev *indio = iio_trigger_get_drvdata(trig);
>> +
>> +	if (indio != indio_dev)
>> +		return -EINVAL;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL(st_sensors_validate_device);
>> +
>>  MODULE_AUTHOR("Denis Ciocca <denis.ciocca@st.com>");
>>  MODULE_DESCRIPTION("STMicroelectronics ST-sensors trigger");
>>  MODULE_LICENSE("GPL v2");
>> diff --git a/drivers/iio/gyro/st_gyro_buffer.c b/drivers/iio/gyro/st_gyro_buffer.c
>> index d67b17b6a7aa..a5377044e42f 100644
>> --- a/drivers/iio/gyro/st_gyro_buffer.c
>> +++ b/drivers/iio/gyro/st_gyro_buffer.c
>> @@ -91,7 +91,7 @@ static const struct iio_buffer_setup_ops st_gyro_buffer_setup_ops = {
>>  
>>  int st_gyro_allocate_ring(struct iio_dev *indio_dev)
>>  {
>> -	return iio_triggered_buffer_setup(indio_dev, &iio_pollfunc_store_time,
>> +	return iio_triggered_buffer_setup(indio_dev, NULL,
>>  		&st_sensors_trigger_handler, &st_gyro_buffer_setup_ops);
>>  }
>>  
>> diff --git a/drivers/iio/gyro/st_gyro_core.c b/drivers/iio/gyro/st_gyro_core.c
>> index be9057e89dc3..242a3e3c88e4 100644
>> --- a/drivers/iio/gyro/st_gyro_core.c
>> +++ b/drivers/iio/gyro/st_gyro_core.c
>> @@ -408,6 +408,7 @@ static const struct iio_info gyro_info = {
>>  static const struct iio_trigger_ops st_gyro_trigger_ops = {
>>  	.owner = THIS_MODULE,
>>  	.set_trigger_state = ST_GYRO_TRIGGER_SET_STATE,
>> +	.validate_device = st_sensors_validate_device,
>>  };
>>  #define ST_GYRO_TRIGGER_OPS (&st_gyro_trigger_ops)
>>  #else
>> diff --git a/drivers/iio/magnetometer/st_magn_buffer.c b/drivers/iio/magnetometer/st_magn_buffer.c
>> index ecd3bd0a9769..0a9e8fadfa9d 100644
>> --- a/drivers/iio/magnetometer/st_magn_buffer.c
>> +++ b/drivers/iio/magnetometer/st_magn_buffer.c
>> @@ -82,7 +82,7 @@ static const struct iio_buffer_setup_ops st_magn_buffer_setup_ops = {
>>  
>>  int st_magn_allocate_ring(struct iio_dev *indio_dev)
>>  {
>> -	return iio_triggered_buffer_setup(indio_dev, &iio_pollfunc_store_time,
>> +	return iio_triggered_buffer_setup(indio_dev, NULL,
>>  		&st_sensors_trigger_handler, &st_magn_buffer_setup_ops);
>>  }
>>  
>> diff --git a/drivers/iio/magnetometer/st_magn_core.c b/drivers/iio/magnetometer/st_magn_core.c
>> index 62036d2a9956..8250fc322c56 100644
>> --- a/drivers/iio/magnetometer/st_magn_core.c
>> +++ b/drivers/iio/magnetometer/st_magn_core.c
>> @@ -572,6 +572,7 @@ static const struct iio_info magn_info = {
>>  static const struct iio_trigger_ops st_magn_trigger_ops = {
>>  	.owner = THIS_MODULE,
>>  	.set_trigger_state = ST_MAGN_TRIGGER_SET_STATE,
>> +	.validate_device = st_sensors_validate_device,
>>  };
>>  #define ST_MAGN_TRIGGER_OPS (&st_magn_trigger_ops)
>>  #else
>> diff --git a/drivers/iio/pressure/st_pressure_buffer.c b/drivers/iio/pressure/st_pressure_buffer.c
>> index 2ff53f222352..99468d0a64e7 100644
>> --- a/drivers/iio/pressure/st_pressure_buffer.c
>> +++ b/drivers/iio/pressure/st_pressure_buffer.c
>> @@ -82,7 +82,7 @@ static const struct iio_buffer_setup_ops st_press_buffer_setup_ops = {
>>  
>>  int st_press_allocate_ring(struct iio_dev *indio_dev)
>>  {
>> -	return iio_triggered_buffer_setup(indio_dev, &iio_pollfunc_store_time,
>> +	return iio_triggered_buffer_setup(indio_dev, NULL,
>>  		&st_sensors_trigger_handler, &st_press_buffer_setup_ops);
>>  }
>>  
>> diff --git a/drivers/iio/pressure/st_pressure_core.c b/drivers/iio/pressure/st_pressure_core.c
>> index 9e9b72a8f18f..b48285739246 100644
>> --- a/drivers/iio/pressure/st_pressure_core.c
>> +++ b/drivers/iio/pressure/st_pressure_core.c
>> @@ -425,6 +425,7 @@ static const struct iio_info press_info = {
>>  static const struct iio_trigger_ops st_press_trigger_ops = {
>>  	.owner = THIS_MODULE,
>>  	.set_trigger_state = ST_PRESS_TRIGGER_SET_STATE,
>> +	.validate_device = st_sensors_validate_device,
>>  };
>>  #define ST_PRESS_TRIGGER_OPS (&st_press_trigger_ops)
>>  #else
>> diff --git a/include/linux/iio/common/st_sensors.h b/include/linux/iio/common/st_sensors.h
>> index d029ffac0d69..99403b19092f 100644
>> --- a/include/linux/iio/common/st_sensors.h
>> +++ b/include/linux/iio/common/st_sensors.h
>> @@ -223,6 +223,8 @@ struct st_sensor_settings {
>>   * @get_irq_data_ready: Function to get the IRQ used for data ready signal.
>>   * @tf: Transfer function structure used by I/O operations.
>>   * @tb: Transfer buffers and mutex used by I/O operations.
>> + * @hw_irq_trigger: if we're using the hardware interrupt on the sensor.
>> + * @hw_timestamp: Latest timestamp from the interrupt handler, when in use.
>>   */
>>  struct st_sensor_data {
>>  	struct device *dev;
>> @@ -247,6 +249,9 @@ struct st_sensor_data {
>>  
>>  	const struct st_sensor_transfer_function *tf;
>>  	struct st_sensor_transfer_buffer tb;
>> +
>> +	bool hw_irq_trigger;
>> +	s64 hw_timestamp;
>>  };
>>  
>>  #ifdef CONFIG_IIO_BUFFER
>> @@ -260,7 +265,8 @@ int st_sensors_allocate_trigger(struct iio_dev *indio_dev,
>>  				const struct iio_trigger_ops *trigger_ops);
>>  
>>  void st_sensors_deallocate_trigger(struct iio_dev *indio_dev);
>> -
>> +int st_sensors_validate_device(struct iio_trigger *trig,
>> +			       struct iio_dev *indio_dev);
>>  #else
>>  static inline int st_sensors_allocate_trigger(struct iio_dev *indio_dev,
>>  				const struct iio_trigger_ops *trigger_ops)
>> @@ -271,6 +277,7 @@ static inline void st_sensors_deallocate_trigger(struct iio_dev *indio_dev)
>>  {
>>  	return;
>>  }
>> +#define st_sensors_validate_device NULL
>>  #endif
>>  
>>  int st_sensors_init_sensor(struct iio_dev *indio_dev,
>>
> 
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