Re: [PATCH 2/2] iio: make stm32 trigger driver use INDIO_HARDWARE_TRIGGERED mode

[William Breathitt Gray <vilhelm.gray@gmail.com>]

On Sun, May 07, 2017 at 02:49:16PM +0100, Jonathan Cameron wrote:
>On 01/05/17 01:50, Jonathan Cameron wrote:
>> On 27/04/17 14:29, Benjamin Gaignard wrote:
>>> Add validate function to be use to use the correct trigger.
>>> Add an attribute to configure device mode like for quadrature and
>>> enable modes
>>>
>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
>> Hmm.  I think I quite like this as an approach but have changed my
>> mind several times over the last few days :)
>> 
>> Hence I'd ideally like some more opinions and will be leaving it
>> on the list for at least a short time longer.
>> 
>> It's missed the current merge window anyway so plenty of time to
>> tick off this last element of your support.
>> 
>> I also just checked and our docs for the existing modes is rubbish
>> (or I can't find it with a quick grep ;)
>> so we should tidy that up and add some description of this as well.	
>Still looking for more input on this!
>
>Lars - do you have time for a quick look?
>
>No real rush though as we are early in the cycle.
>
>Thanks,
>
>Jonathan

I haven't used triggers before in my drivers so perhaps I can provide
the naive perspective of someone approaching the API for the first time.

>From what I gather, the INDIO_BUFFERED_TRIGGERED option is used for
triggers associated with a buffer; for example, a device keeping track
of ambient temperature may periodically sample its sensors and store the
data in a buffer for later evaluation.

The INDIO_EVENT_TRIGGERED option appears to be used for triggers
associated with some sort of event; for example, a threshold voltage is
reached on an ADC device.

I'm having trouble groking how the INDIO_HARDWARE_TRIGGERED option
differs from the INDIO_EVENT_TRIGGERED option. It looks like the
INDIO_HARDWARE_TRIGGERED option is used in this case to associate a
trigger with a clock edge (first timer chained to second timer).
Wouldn't an INDIO_EVENT_TRIGGERED option be sufficient in this case
where the event is defined as the clock edge input to the second timer?

William Breathitt Gray

>> 
>> Jonathan
>>> ---
>>>  .../ABI/testing/sysfs-bus-iio-timer-stm32          | 15 ++++++
>>>  drivers/iio/trigger/stm32-timer-trigger.c          | 61 ++++++++++++++++++++++
>>>  2 files changed, 76 insertions(+)
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32 b/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>>> index 230020e..cccdf57 100644
>>> --- a/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>>> @@ -90,3 +90,18 @@ Description:
>>>  			Counting is enabled on rising edge of the connected
>>>  			trigger, and remains enabled for the duration of this
>>>  			selected mode.
>>> +
>>> +What:		/sys/bus/iio/devices/iio:deviceX/in_count_trigger_mode_available
>>> +KernelVersion:	4.13
>>> +Contact:	benjamin.gaignard@st.com
>>> +Description:
>>> +		Reading returns the list possible trigger modes.
>>> +
>>> +What:		/sys/bus/iio/devices/iio:deviceX/in_count0_trigger_mode
>>> +KernelVersion:	4.13
>>> +Contact:	benjamin.gaignard@st.com
>>> +Description:
>>> +		Configure the device counter trigger mode
>>> +		counting direction is set by in_count0_count_direction
>>> +		attribute and the counter is clocked by the connected trigger
>>> +		rising edges.
>>> diff --git a/drivers/iio/trigger/stm32-timer-trigger.c b/drivers/iio/trigger/stm32-timer-trigger.c
>>> index 0f1a2cf..7c6e90e 100644
>>> --- a/drivers/iio/trigger/stm32-timer-trigger.c
>>> +++ b/drivers/iio/trigger/stm32-timer-trigger.c
>>> @@ -347,12 +347,70 @@ static int stm32_counter_write_raw(struct iio_dev *indio_dev,
>>>  	return -EINVAL;
>>>  }
>>>  
>>> +static int stm32_counter_validate_trigger(struct iio_dev *indio_dev,
>>> +					  struct iio_trigger *trig)
>>> +{
>>> +	struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>> +	const char * const *cur = priv->valids;
>>> +	unsigned int i = 0;
>>> +
>>> +	if (!is_stm32_timer_trigger(trig))
>>> +		return -EINVAL;
>>> +
>>> +	while (cur && *cur) {
>>> +		if (!strncmp(trig->name, *cur, strlen(trig->name))) {
>>> +			regmap_update_bits(priv->regmap,
>>> +					   TIM_SMCR, TIM_SMCR_TS,
>>> +					   i << TIM_SMCR_TS_SHIFT);
>>> +			return 0;
>>> +		}
>>> +		cur++;
>>> +		i++;
>>> +	}
>>> +
>>> +	return -EINVAL;
>>> +}
>>> +
>>>  static const struct iio_info stm32_trigger_info = {
>>>  	.driver_module = THIS_MODULE,
>>> +	.validate_trigger = stm32_counter_validate_trigger,
>>>  	.read_raw = stm32_counter_read_raw,
>>>  	.write_raw = stm32_counter_write_raw
>>>  };
>>>  
>>> +static const char *const stm32_trigger_modes[] = {
>>> +	"trigger",
>>> +};
>>> +
>>> +static int stm32_set_trigger_mode(struct iio_dev *indio_dev,
>>> +				  const struct iio_chan_spec *chan,
>>> +				  unsigned int mode)
>>> +{
>>> +	struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>> +
>>> +	regmap_update_bits(priv->regmap, TIM_SMCR, TIM_SMCR_SMS, TIM_SMCR_SMS);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int stm32_get_trigger_mode(struct iio_dev *indio_dev,
>>> +				  const struct iio_chan_spec *chan)
>>> +{
>>> +	struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>> +	u32 smcr;
>>> +
>>> +	regmap_read(priv->regmap, TIM_SMCR, &smcr);
>>> +
>>> +	return smcr == TIM_SMCR_SMS ? 0 : -EINVAL;
>>> +}
>>> +
>>> +static const struct iio_enum stm32_trigger_mode_enum = {
>>> +	.items = stm32_trigger_modes,
>>> +	.num_items = ARRAY_SIZE(stm32_trigger_modes),
>>> +	.set = stm32_set_trigger_mode,
>>> +	.get = stm32_get_trigger_mode
>>> +};
>>> +
>>>  static const char *const stm32_enable_modes[] = {
>>>  	"always",
>>>  	"gated",
>>> @@ -536,6 +594,8 @@ static ssize_t stm32_count_set_preset(struct iio_dev *indio_dev,
>>>  	IIO_ENUM_AVAILABLE("quadrature_mode", &stm32_quadrature_mode_enum),
>>>  	IIO_ENUM("enable_mode", IIO_SEPARATE, &stm32_enable_mode_enum),
>>>  	IIO_ENUM_AVAILABLE("enable_mode", &stm32_enable_mode_enum),
>>> +	IIO_ENUM("trigger_mode", IIO_SEPARATE, &stm32_trigger_mode_enum),
>>> +	IIO_ENUM_AVAILABLE("trigger_mode", &stm32_trigger_mode_enum),
>>>  	{}
>>>  };
>>>  
>>> @@ -560,6 +620,7 @@ static struct stm32_timer_trigger *stm32_setup_counter_device(struct device *dev
>>>  	indio_dev->name = dev_name(dev);
>>>  	indio_dev->dev.parent = dev;
>>>  	indio_dev->info = &stm32_trigger_info;
>>> +	indio_dev->modes = INDIO_HARDWARE_TRIGGERED;
>>>  	indio_dev->num_channels = 1;
>>>  	indio_dev->channels = &stm32_trigger_channel;
>>>  	indio_dev->dev.of_node = dev->of_node;
>>>
>> 
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>