Date:   Tue, 6 Jun 2017 11:41:43 +0200
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     William Breathitt Gray <vilhelm.gray@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-iio@...r.kernel.org, Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>, mwelling@...e.org,
        Fabrice Gasnier <fabrice.gasnier@...com>,
        Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
        Benjamin Gaignard <benjamin.gaignard@...com>
Subject: Re: [PATCH 2/2] iio: make stm32 trigger driver use
 INDIO_HARDWARE_TRIGGERED mode

2017-05-14 18:02 GMT+02:00 Jonathan Cameron <jic23@...nel.org>:
> On 09/05/17 08:46, Benjamin Gaignard wrote:
>>
>> 2017-05-08 17:17 GMT+02:00 William Breathitt Gray
>> <vilhelm.gray@...il.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@...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?
>>
>>
>> The main difference I have introduce between INDIO_EVENT_TRIGGERED and
>> INDIO_HARDWARE_TRIGGERED is that this last one doesn't have poll function
>> (i.e. userland can't wait on the event).
>
> INDIO_EVENT_TRIGGERED has a different intent as well. It's about doing
> synchronized acquisition of whether a threshold has been passed or not.
> It's used for comparator chips that don't have anything else to them.
> Right now the only user is the hi8435.  It took a lot of bouncing backwards
> and forwards before we came up with this way of handling that chip.
> So what you have is a comparator with lots of channels, but it will only
> give you info on which are above threshold when you ask it (not interrupts
> or internal clocking).  Odd beasts typically used in PLCs where you have
> a scan function polling the lot in realtime very 5 msecs or so.
>
>> For me userland doesn't need to be informed of each clock rising edge.
>> More generally this new mode can be used when the event can't/doesn't need
>> be
>> notified to userland which is the case in my hardware where it is a
>> signal on internal
>> wire.
>
> Absolutely.  The 'fun' corner case is triggers that 'can' be exposed to
> userspace
> (so there is an interrupt available) but don't have to be to run the
> capture on a tightly coupled bit of hardware.  Conceptually there is a
> hardware
> implementation of the interrupt handler available.

What can I do to progress in implementation of INDIO_HARDWARE_TRIGGERED ?
Do it feel sensible for you to use it ?


>
>>
>>>
>>> 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@...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@...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;
>>>>>>
>>>>>
>>>>> --
>>>>> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
>>>>> the body of a message to majordomo@...r.kernel.org
>>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>>
>>>>
>>
>>
>>
>



-- 
Benjamin Gaignard

Graphic Study Group

Linaro.org │ Open source software for ARM SoCs

Follow Linaro: Facebook | Twitter | Blog

Powered by blists - more mailing lists