[PATCH v6 6/8] IIO: add STM32 timer trigger driver

Jonathan Cameron jic23 at jic23.retrosnub.co.uk
Tue Jan 3 09:16:26 PST 2017



On 3 January 2017 09:23:34 GMT+00:00, Benjamin Gaignard <benjamin.gaignard at linaro.org> wrote:
>2017-01-02 19:22 GMT+01:00 Jonathan Cameron <jic23 at kernel.org>:
>> On 02/01/17 08:46, Benjamin Gaignard wrote:
>>> 2016-12-30 22:12 GMT+01:00 Jonathan Cameron <jic23 at kernel.org>:
>>>> On 09/12/16 14:15, Benjamin Gaignard wrote:
>>>>> Timers IPs can be used to generate triggers for other IPs like
>>>>> DAC, ADC or other timers.
>>>>> Each trigger may result of timer internals signals like counter
>enable,
>>>>> reset or edge, this configuration could be done through
>"master_mode"
>>>>> device attribute.
>>>>>
>>>>> A timer device could be triggered by other timers, we use the
>trigger
>>>>> name and is_stm32_iio_timer_trigger() function to distinguish them
>>>>> and configure IP input switch.
>>>>>
>>>>> Timer may also decide on which event (edge, level) they could
>>>>> be activated by a trigger, this configuration is done by writing
>in
>>>>> "slave_mode" device attribute.
>>>>>
>>>>> Since triggers could also be used by DAC or ADC their names are
>defined
>>>>> in include/ nux/iio/timer/stm32-timer-trigger.h so those IPs will
>be able
>>>>> to configure themselves in valid_trigger function
>>>>>
>>>>> Trigger have a "sampling_frequency" attribute which allow to
>configure
>>>>> timer sampling frequency without using PWM interface
>>>>>
>>>>> version 5:
>>>>> - simplify tables of triggers
>>>>> - only create an IIO device when needed
>>>>>
>>>>> version 4:
>>>>> - get triggers configuration from "reg" in DT
>>>>> - add tables of triggers
>>>>> - sampling frequency is enable/disable when writing in trigger
>>>>>   sampling_frequency attribute
>>>>> - no more use of interruptions
>>>>>
>>>>> version 3:
>>>>> - change compatible to "st,stm32-timer-trigger"
>>>>> - fix attributes access right
>>>>> - use string instead of int for master_mode and slave_mode
>>>>> - document device attributes in sysfs-bus-iio-timer-stm32
>>>>>
>>>>> version 2:
>>>>> - keep only one compatible
>>>>> - use st,input-triggers-names and st,output-triggers-names
>>>>>   to know which triggers are accepted and/or create by the device
>>>> Firstly, sorry it has taken me so long to get back to this.
>>>>
>>>> I'm still not keen on this use of iio_device elements just to act
>as
>>>> glue between triggers.  I think we need to work out a more light
>weight
>>>> way to do this.  As you are only using them for validation and to
>provide
>>>> somewhere to hang the control attibutes off, there is nothing
>stopping us
>>>> moving that over to the iio_trigger instead which would avoid the
>messy
>>>> duality going on here.
>>>
>>> I have add an iio_device because each hardware can generate multiple
>>> triggers (up to 5: trgo, ch 1...4) and slave_mode attribute will
>impact all the
>>> triggers of a device. For me it was making sense to centralize that
>in an
>>> iio_device rather than having an attribute "shared" (from hardware
>>> point of view)
>>> on multiple triggers.
>>> Since master_mode attribute is only used by trgo and not impact
>ch1...4
>>> triggers I will move it to trigger instead of the iio_device.
>>>
>>> I also wanted to be able to connect triggers on a iio_device as I
>>> could do for an
>>> ADC with a command like 'echo "tim1_trgo" >
>iio_deviceX/trigger/current_trigger'
>> This is interesting, but with a bit of refactoring I would think it
>would
>> be possible to share some of that code thus allowing non IIO devices
>to
>> bind to triggers.  Ultimately I want to be able to bind a trigger to
>> a trigger - I appreciate here the topology is more limited than that
>> so some complexity comes in.
>>
>> My gut feeling is that representing that topology explicitly is hard
>> to do in a remotely general way, but lets try it and see.
>> We run into this sort of interdependency issue between different bits
>of
>> the hardware all the time.  Setting a value somewhere effects the
>configuration
>> elsewhere - often the best plan is to just let that happen and leave
>it up to
>> userspace to check for changes if it cares.
>
>okay
>
>>> If I change that to parent_trigger attribute it change this behavior
>>> and I will have to
>>> duplicated what is done in iio_trigger_write_current() to find and
>>> validate triggers.
>> I get the reasoning, but we still end up with something represented
>> by an IIO device that isn't providing any channels at all. It's
>simply
>> using some of the infrastructure.  To my mind it is 'something else'
>> and should be represented as such.  I have no problem at all with
>> you registering additional elements in /sysfs/bus/iio/ to represent
>> these shared elements - we already have drivers that do that to
>> provide some centralized infrastructure (e.g. the sysfs-trigger)
>
>My hardware block are timers maybe I can add a channel type "IIO_TIMER"
>and declare a channel with info_mask_separate =
>BIT(IIO_CHAN_INFO_SAMP_FREQ)
>so I will be able to write/read sampling frequency on IIO device.
Hmm stretching a point. There aren't really input or output channels. 

Still not convinced there should be any IIO devices near this at all.
>
>> I'm worried about the scope spread we get for an IIO device
>otherwise.
>> They serve a well defined purpose at the moment, and that isn't what
>> is happening here.
>>
>> So my gut feeling is we are better deliberately not representing the
>> inter dependence and claiming all triggers we are creating are
>> independent.  That way we can have a nice generic infrastructure
>> that will work in all cases (be it pushing the sanity checking to
>> userspace).
>>
>> So each trigger has direct access to what controls it.  Changing
>anything
>> can effect other triggers in weird ways.
>>
>> I'm finding it hard to see anything else generalizing sufficiently
>> as we'll always get cases where we can't represent the topology
>without
>> diving into the complexity of something like the media controller
>> framework.
>>
>> Jonathan
>>>
>>>> I might still be missing something though!
>>>>
>>>> You would only I think need 3 attributes
>>>>
>>>> parrent_trigger
>>>> and something like your master_mode and slave_mode attributes.
>>>>
>>>> The parrent_trigger would need some validation etc, but if we keep
>it
>>>> within this driver initially that won't be hard to do. Checking the
>device
>>>> parent matches will do most of it.
>>>>
>>>> Jonathan
>>>>>
>>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard at st.com>
>>>>> ---
>>>>>  .../ABI/testing/sysfs-bus-iio-timer-stm32          |  55 +++
>>>>>  drivers/iio/Kconfig                                |   2 +-
>>>>>  drivers/iio/Makefile                               |   1 +
>>>>>  drivers/iio/timer/Kconfig                          |  13 +
>>>>>  drivers/iio/timer/Makefile                         |   1 +
>>>>>  drivers/iio/timer/stm32-timer-trigger.c            | 466
>+++++++++++++++++++++
>>>>>  drivers/iio/trigger/Kconfig                        |   1 -
>>>>>  include/linux/iio/timer/stm32-timer-trigger.h      |  62 +++
>>>>>  8 files changed, 599 insertions(+), 2 deletions(-)
>>>>>  create mode 100644
>Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>>>>>  create mode 100644 drivers/iio/timer/Kconfig
>>>>>  create mode 100644 drivers/iio/timer/Makefile
>>>>>  create mode 100644 drivers/iio/timer/stm32-timer-trigger.c
>>>>>  create mode 100644 include/linux/iio/timer/stm32-timer-trigger.h
>>>>>
>>>>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>b/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>>>>> new file mode 100644
>>>>> index 0000000..26583dd
>>>>> --- /dev/null
>>>>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>>>>> @@ -0,0 +1,55 @@
>>>>> +What:               
>/sys/bus/iio/devices/iio:deviceX/master_mode_available
>>>>> +KernelVersion:       4.10
>>>>> +Contact:     benjamin.gaignard at st.com
>>>>> +Description:
>>>>> +             Reading returns the list possible master modes which
>are:
>>>>> +             - "reset"     : The UG bit from the TIMx_EGR
>register is used as trigger output (TRGO).
>>>>> +             - "enable"    : The Counter Enable signal CNT_EN is
>used as trigger output.
>>>>> +             - "update"    : The update event is selected as
>trigger output.
>>>>> +                             For instance a master timer can then
>be used as a prescaler for a slave timer.
>>>>> +             - "compare_pulse" : The trigger output send a
>positive pulse when the CC1IF flag is to be set.
>>>>> +             - "OC1REF"    : OC1REF signal is used as trigger
>output.
>>>>> +             - "OC2REF"    : OC2REF signal is used as trigger
>output.
>>>>> +             - "OC3REF"    : OC3REF signal is used as trigger
>output.
>>>>> +             - "OC4REF"    : OC4REF signal is used as trigger
>output.
>>>>> +
>>>>> +What:                /sys/bus/iio/devices/iio:deviceX/master_mode
>>>>> +KernelVersion:       4.10
>>>>> +Contact:     benjamin.gaignard at st.com
>>>>> +Description:
>>>>> +             Reading returns the current master modes.
>>>>> +             Writing set the master mode
>>>>> +
>>>>> +What:               
>/sys/bus/iio/devices/iio:deviceX/slave_mode_available
>>>>> +KernelVersion:       4.10
>>>>> +Contact:     benjamin.gaignard at st.com
>>>>> +Description:
>>>>> +             Reading returns the list possible slave modes which
>are:
>>>>> +             - "disabled"  : The prescaler is clocked directly by
>the internal clock.
>>>>> +             - "encoder_1" : Counter counts up/down on TI2FP1
>edge depending on TI1FP2 level.
>>>>> +             - "encoder_2" : Counter counts up/down on TI1FP2
>edge depending on TI2FP1 level.
>>>>> +             - "encoder_3" : Counter counts up/down on both
>TI1FP1 and TI2FP2 edges depending
>>>>> +                             on the level of the other input.
>>>>> +             - "reset"     : Rising edge of the selected trigger
>input reinitializes the counter
>>>>> +                             and generates an update of the
>registers.
>>>>> +             - "gated"     : The counter clock is enabled when
>the trigger input is high.
>>>>> +                             The counter stops (but is not reset)
>as soon as the trigger becomes low.
>>>>> +                             Both start and stop of the counter
>are controlled.
>>>>> +             - "trigger"   : The counter starts at a rising edge
>of the trigger TRGI (but it is not
>>>>> +                             reset). Only the start of the
>counter is controlled.
>>>>> +             - "external_clock": Rising edges of the selected
>trigger (TRGI) clock the counter.
>>>>> +
>>>>> +What:                /sys/bus/iio/devices/iio:deviceX/slave_mode
>>>>> +KernelVersion:       4.10
>>>>> +Contact:     benjamin.gaignard at st.com
>>>>> +Description:
>>>>> +             Reading returns the current slave mode.
>>>>> +             Writing set the slave mode
>>>>> +
>>>>> +What:               
>/sys/bus/iio/devices/triggerX/sampling_frequency
>>>>> +KernelVersion:       4.10
>>>>> +Contact:     benjamin.gaignard at st.com
>>>>> +Description:
>>>>> +             Reading returns the current sampling frequency.
>>>>> +             Writing an value different of 0 set and start
>sampling.
>>>>> +             Writing 0 stop sampling.
>>>>> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
>>>>> index 6743b18..2de2a80 100644
>>>>> --- a/drivers/iio/Kconfig
>>>>> +++ b/drivers/iio/Kconfig
>>>>> @@ -90,5 +90,5 @@ source "drivers/iio/potentiometer/Kconfig"
>>>>>  source "drivers/iio/pressure/Kconfig"
>>>>>  source "drivers/iio/proximity/Kconfig"
>>>>>  source "drivers/iio/temperature/Kconfig"
>>>>> -
>>>>> +source "drivers/iio/timer/Kconfig"
>>>>>  endif # IIO
>>>>> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
>>>>> index 87e4c43..b797c08 100644
>>>>> --- a/drivers/iio/Makefile
>>>>> +++ b/drivers/iio/Makefile
>>>>> @@ -32,4 +32,5 @@ obj-y += potentiometer/
>>>>>  obj-y += pressure/
>>>>>  obj-y += proximity/
>>>>>  obj-y += temperature/
>>>>> +obj-y += timer/
>>>>>  obj-y += trigger/
>>>>> diff --git a/drivers/iio/timer/Kconfig b/drivers/iio/timer/Kconfig
>>>>> new file mode 100644
>>>>> index 0000000..e3c21f2
>>>>> --- /dev/null
>>>>> +++ b/drivers/iio/timer/Kconfig
>>>>> @@ -0,0 +1,13 @@
>>>>> +#
>>>>> +# Timers drivers
>>>>> +
>>>>> +menu "Timers"
>>>>> +
>>>>> +config IIO_STM32_TIMER_TRIGGER
>>>>> +     tristate "STM32 Timer Trigger"
>>>>> +     depends on (ARCH_STM32 && OF && MFD_STM32_TIMERS) ||
>COMPILE_TEST
>>>>> +     select IIO_TRIGGERED_EVENT
>>>>> +     help
>>>>> +       Select this option to enable STM32 Timer Trigger
>>>>> +
>>>>> +endmenu
>>>>> diff --git a/drivers/iio/timer/Makefile
>b/drivers/iio/timer/Makefile
>>>>> new file mode 100644
>>>>> index 0000000..4ad95ec9
>>>>> --- /dev/null
>>>>> +++ b/drivers/iio/timer/Makefile
>>>>> @@ -0,0 +1 @@
>>>>> +obj-$(CONFIG_IIO_STM32_TIMER_TRIGGER) += stm32-timer-trigger.o
>>>>> diff --git a/drivers/iio/timer/stm32-timer-trigger.c
>b/drivers/iio/timer/stm32-timer-trigger.c
>>>>> new file mode 100644
>>>>> index 0000000..8d16e8f
>>>>> --- /dev/null
>>>>> +++ b/drivers/iio/timer/stm32-timer-trigger.c
>>>>> @@ -0,0 +1,466 @@
>>>>> +/*
>>>>> + * Copyright (C) STMicroelectronics 2016
>>>>> + *
>>>>> + * Author: Benjamin Gaignard <benjamin.gaignard at st.com>
>>>>> + *
>>>>> + * License terms:  GNU General Public License (GPL), version 2
>>>>> + */
>>>>> +
>>>>> +#include <linux/iio/iio.h>
>>>>> +#include <linux/iio/sysfs.h>
>>>>> +#include <linux/iio/timer/stm32-timer-trigger.h>
>>>>> +#include <linux/iio/trigger.h>
>>>>> +#include <linux/iio/triggered_event.h>
>>>>> +#include <linux/interrupt.h>
>>>>> +#include <linux/mfd/stm32-timers.h>
>>>>> +#include <linux/module.h>
>>>>> +#include <linux/platform_device.h>
>>>>> +
>>>>> +#define MAX_TRIGGERS 6
>>>>> +#define MAX_VALIDS 5
>>>>> +
>>>>> +/* List the triggers created by each timer */
>>>>> +static const void *triggers_table[][MAX_TRIGGERS] = {
>>>>> +     { TIM1_TRGO, TIM1_CH1, TIM1_CH2, TIM1_CH3, TIM1_CH4,},
>>>>> +     { TIM2_TRGO, TIM2_CH1, TIM2_CH2, TIM2_CH3, TIM2_CH4,},
>>>>> +     { TIM3_TRGO, TIM3_CH1, TIM3_CH2, TIM3_CH3, TIM3_CH4,},
>>>>> +     { TIM4_TRGO, TIM4_CH1, TIM4_CH2, TIM4_CH3, TIM4_CH4,},
>>>>> +     { TIM5_TRGO, TIM5_CH1, TIM5_CH2, TIM5_CH3, TIM5_CH4,},
>>>>> +     { TIM6_TRGO,},
>>>>> +     { TIM7_TRGO,},
>>>>> +     { TIM8_TRGO, TIM8_CH1, TIM8_CH2, TIM8_CH3, TIM8_CH4,},
>>>>> +     { TIM9_TRGO, TIM9_CH1, TIM9_CH2,},
>>>>> +     { TIM12_TRGO, TIM12_CH1, TIM12_CH2,},
>>>>> +};
>>>>> +
>>>>> +/* List the triggers accepted by each timer */
>>>>> +static const void *valids_table[][MAX_VALIDS] = {
>>>>> +     { TIM5_TRGO, TIM2_TRGO, TIM4_TRGO, TIM3_TRGO,},
>>>>> +     { TIM1_TRGO, TIM8_TRGO, TIM3_TRGO, TIM4_TRGO,},
>>>>> +     { TIM1_TRGO, TIM8_TRGO, TIM5_TRGO, TIM4_TRGO,},
>>>>> +     { TIM1_TRGO, TIM2_TRGO, TIM3_TRGO, TIM8_TRGO,},
>>>>> +     { TIM2_TRGO, TIM3_TRGO, TIM4_TRGO, TIM8_TRGO,},
>>>>> +     { }, /* timer 6 */
>>>>> +     { }, /* timer 7 */
>>>>> +     { TIM1_TRGO, TIM2_TRGO, TIM4_TRGO, TIM5_TRGO,},
>>>>> +     { TIM2_TRGO, TIM3_TRGO,},
>>>>> +     { TIM4_TRGO, TIM5_TRGO,},
>>>>> +};
>>>>> +
>>>>> +struct stm32_timer_trigger {
>>>>> +     struct device *dev;
>>>>> +     struct regmap *regmap;
>>>>> +     struct clk *clk;
>>>>> +     u32 max_arr;
>>>>> +     const void *triggers;
>>>>> +     const void *valids;
>>>>> +};
>>>>> +
>>>>> +static int stm32_timer_start(struct stm32_timer_trigger *priv,
>>>>> +                          unsigned int frequency)
>>>>> +{
>>>>> +     unsigned long long prd, div;
>>>>> +     int prescaler = 0;
>>>>> +     u32 ccer, cr1;
>>>>> +
>>>>> +     /* Period and prescaler values depends of clock rate */
>>>>> +     div = (unsigned long long)clk_get_rate(priv->clk);
>>>>> +
>>>>> +     do_div(div, frequency);
>>>>> +
>>>>> +     prd = div;
>>>>> +
>>>>> +     /*
>>>>> +      * Increase prescaler value until we get a result that fit
>>>>> +      * with auto reload register maximum value.
>>>>> +      */
>>>>> +     while (div > priv->max_arr) {
>>>>> +             prescaler++;
>>>>> +             div = prd;
>>>>> +             do_div(div, (prescaler + 1));
>>>>> +     }
>>>>> +     prd = div;
>>>>> +
>>>>> +     if (prescaler > MAX_TIM_PSC) {
>>>>> +             dev_err(priv->dev, "prescaler exceeds the maximum
>value\n");
>>>>> +             return -EINVAL;
>>>>> +     }
>>>>> +
>>>>> +     /* Check if nobody else use the timer */
>>>>> +     regmap_read(priv->regmap, TIM_CCER, &ccer);
>>>>> +     if (ccer & TIM_CCER_CCXE)
>>>>> +             return -EBUSY;
>>>>> +
>>>>> +     regmap_read(priv->regmap, TIM_CR1, &cr1);
>>>>> +     if (!(cr1 & TIM_CR1_CEN))
>>>>> +             clk_enable(priv->clk);
>>>>> +
>>>>> +     regmap_write(priv->regmap, TIM_PSC, prescaler);
>>>>> +     regmap_write(priv->regmap, TIM_ARR, prd - 1);
>>>>> +     regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE,
>TIM_CR1_ARPE);
>>>>> +
>>>>> +     /* Force master mode to update mode */
>>>>> +     regmap_update_bits(priv->regmap, TIM_CR2, TIM_CR2_MMS,
>0x20);
>>>>> +
>>>>> +     /* Make sure that registers are updated */
>>>>> +     regmap_update_bits(priv->regmap, TIM_EGR, TIM_EGR_UG,
>TIM_EGR_UG);
>>>>> +
>>>>> +     /* Enable controller */
>>>>> +     regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN,
>TIM_CR1_CEN);
>>>>> +
>>>>> +     return 0;
>>>>> +}
>>>>> +
>>>>> +static void stm32_timer_stop(struct stm32_timer_trigger *priv)
>>>>> +{
>>>>> +     u32 ccer, cr1;
>>>>> +
>>>>> +     regmap_read(priv->regmap, TIM_CCER, &ccer);
>>>>> +     if (ccer & TIM_CCER_CCXE)
>>>>> +             return;
>>>>> +
>>>>> +     regmap_read(priv->regmap, TIM_CR1, &cr1);
>>>>> +     if (cr1 & TIM_CR1_CEN)
>>>>> +             clk_disable(priv->clk);
>>>>> +
>>>>> +     /* Stop timer */
>>>>> +     regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0);
>>>>> +     regmap_write(priv->regmap, TIM_PSC, 0);
>>>>> +     regmap_write(priv->regmap, TIM_ARR, 0);
>>>>> +}
>>>>> +
>>>>> +static ssize_t stm32_tt_store_frequency(struct device *dev,
>>>>> +                                     struct device_attribute
>*attr,
>>>>> +                                     const char *buf, size_t len)
>>>>> +{
>>>>> +     struct iio_trigger *trig = to_iio_trigger(dev);
>>>>> +     struct stm32_timer_trigger *priv =
>iio_trigger_get_drvdata(trig);
>>>>> +     unsigned int freq;
>>>>> +     int ret;
>>>>> +
>>>>> +     ret = kstrtouint(buf, 10, &freq);
>>>>> +     if (ret)
>>>>> +             return ret;
>>>>> +
>>>>> +     if (freq == 0) {
>>>>> +             stm32_timer_stop(priv);
>>>>> +     } else {
>>>>> +             ret = stm32_timer_start(priv, freq);
>>>>> +             if (ret)
>>>>> +                     return ret;
>>>>> +     }
>>>>> +
>>>>> +     return len;
>>>>> +}
>>>>> +
>>>>> +static ssize_t stm32_tt_read_frequency(struct device *dev,
>>>>> +                                    struct device_attribute
>*attr, char *buf)
>>>>> +{
>>>>> +     struct iio_trigger *trig = to_iio_trigger(dev);
>>>>> +     struct stm32_timer_trigger *priv =
>iio_trigger_get_drvdata(trig);
>>>>> +     u32 psc, arr, cr1;
>>>>> +     unsigned long long freq = 0;
>>>>> +
>>>>> +     regmap_read(priv->regmap, TIM_CR1, &cr1);
>>>>> +     regmap_read(priv->regmap, TIM_PSC, &psc);
>>>>> +     regmap_read(priv->regmap, TIM_ARR, &arr);
>>>>> +
>>>>> +     if (psc && arr && (cr1 & TIM_CR1_CEN)) {
>>>>> +             freq = (unsigned long long)clk_get_rate(priv->clk);
>>>>> +             do_div(freq, psc);
>>>>> +             do_div(freq, arr);
>>>>> +     }
>>>>> +
>>>>> +     return sprintf(buf, "%d\n", (unsigned int)freq);
>>>>> +}
>>>>> +
>>>>> +static IIO_DEV_ATTR_SAMP_FREQ(0660,
>>>>> +                           stm32_tt_read_frequency,
>>>>> +                           stm32_tt_store_frequency);
>>>>> +
>>>>> +static struct attribute *stm32_trigger_attrs[] = {
>>>>> +     &iio_dev_attr_sampling_frequency.dev_attr.attr,
>>>>> +     NULL,
>>>>> +};
>>>>> +
>>>>> +static const struct attribute_group stm32_trigger_attr_group = {
>>>>> +     .attrs = stm32_trigger_attrs,
>>>>> +};
>>>>> +
>>>>> +static const struct attribute_group *stm32_trigger_attr_groups[]
>= {
>>>>> +     &stm32_trigger_attr_group,
>>>>> +     NULL,
>>>>> +};
>>>>> +
>>>>> +static char *master_mode_table[] = {
>>>>> +     "reset",
>>>>> +     "enable",
>>>>> +     "update",
>>>>> +     "compare_pulse",
>>>>> +     "OC1REF",
>>>>> +     "OC2REF",
>>>>> +     "OC3REF",
>>>>> +     "OC4REF"
>>>>> +};
>>>>> +
>>>>> +static ssize_t stm32_tt_show_master_mode(struct device *dev,
>>>>> +                                      struct device_attribute
>*attr,
>>>>> +                                      char *buf)
>>>>> +{
>>>>> +     struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>>>>> +     struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>>> +     u32 cr2;
>>>>> +
>>>>> +     regmap_read(priv->regmap, TIM_CR2, &cr2);
>>>>> +     cr2 = (cr2 & TIM_CR2_MMS) >> TIM_CR2_MMS_SHIFT;
>>>>> +
>>>>> +     return snprintf(buf, PAGE_SIZE, "%s\n",
>master_mode_table[cr2]);
>>>>> +}
>>>>> +
>>>>> +static ssize_t stm32_tt_store_master_mode(struct device *dev,
>>>>> +                                       struct device_attribute
>*attr,
>>>>> +                                       const char *buf, size_t
>len)
>>>>> +{
>>>>> +     struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>>>>> +     struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>>> +     int i;
>>>>> +
>>>>> +     for (i = 0; i < ARRAY_SIZE(master_mode_table); i++) {
>>>>> +             if (!strncmp(master_mode_table[i], buf,
>>>>> +                          strlen(master_mode_table[i]))) {
>>>>> +                     regmap_update_bits(priv->regmap, TIM_CR2,
>>>>> +                                        TIM_CR2_MMS, i <<
>TIM_CR2_MMS_SHIFT);
>>>>> +                     return len;
>>>>> +             }
>>>>> +     }
>>>>> +
>>>>> +     return -EINVAL;
>>>>> +}
>>>>> +
>>>>> +static IIO_CONST_ATTR(master_mode_available,
>>>>> +     "reset enable update compare_pulse OC1REF OC2REF OC3REF
>OC4REF");
>>>>> +
>>>>> +static IIO_DEVICE_ATTR(master_mode, 0660,
>>>>> +                    stm32_tt_show_master_mode,
>>>>> +                    stm32_tt_store_master_mode,
>>>>> +                    0);
>>>>> +
>>>>> +static char *slave_mode_table[] = {
>>>>> +     "disabled",
>>>>> +     "encoder_1",
>>>>> +     "encoder_2",
>>>>> +     "encoder_3",
>>>>> +     "reset",
>>>>> +     "gated",
>>>>> +     "trigger",
>>>>> +     "external_clock",
>>>>> +};
>>>>> +
>>>>> +static ssize_t stm32_tt_show_slave_mode(struct device *dev,
>>>>> +                                     struct device_attribute
>*attr,
>>>>> +                                     char *buf)
>>>>> +{
>>>>> +     struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>>>>> +     struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>>> +     u32 smcr;
>>>>> +
>>>>> +     regmap_read(priv->regmap, TIM_SMCR, &smcr);
>>>>> +     smcr &= TIM_SMCR_SMS;
>>>>> +
>>>>> +     return snprintf(buf, PAGE_SIZE, "%s\n",
>slave_mode_table[smcr]);
>>>>> +}
>>>>> +
>>>>> +static ssize_t stm32_tt_store_slave_mode(struct device *dev,
>>>>> +                                      struct device_attribute
>*attr,
>>>>> +                                      const char *buf, size_t
>len)
>>>>> +{
>>>>> +     struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>>>>> +     struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>>> +     int i;
>>>>> +
>>>>> +     for (i = 0; i < ARRAY_SIZE(slave_mode_table); i++) {
>>>>> +             if (!strncmp(slave_mode_table[i], buf,
>>>>> +                          strlen(slave_mode_table[i]))) {
>>>>> +                     regmap_update_bits(priv->regmap,
>>>>> +                                        TIM_SMCR, TIM_SMCR_SMS,
>i);
>>>>> +                     return len;
>>>>> +             }
>>>>> +     }
>>>>> +
>>>>> +     return -EINVAL;
>>>>> +}
>>>>> +
>>>>> +static IIO_CONST_ATTR(slave_mode_available,
>>>>> +"disabled encoder_1 encoder_2 encoder_3 reset gated trigger
>external_clock");
>>>>> +
>>>>> +static IIO_DEVICE_ATTR(slave_mode, 0660,
>>>>> +                    stm32_tt_show_slave_mode,
>>>>> +                    stm32_tt_store_slave_mode,
>>>>> +                    0);
>>>>> +
>>>>> +static struct attribute *stm32_timer_attrs[] = {
>>>>> +     &iio_dev_attr_master_mode.dev_attr.attr,
>>>>> +     &iio_const_attr_master_mode_available.dev_attr.attr,
>>>>> +     &iio_dev_attr_slave_mode.dev_attr.attr,
>>>>> +     &iio_const_attr_slave_mode_available.dev_attr.attr,
>>>>> +     NULL,
>>>>> +};
>>>>> +
>>>>> +static const struct attribute_group stm32_timer_attr_group = {
>>>>> +     .attrs = stm32_timer_attrs,
>>>>> +};
>>>>> +
>>>>> +static const struct iio_trigger_ops timer_trigger_ops = {
>>>>> +     .owner = THIS_MODULE,
>>>>> +};
>>>>> +
>>>>> +static int stm32_setup_iio_triggers(struct stm32_timer_trigger
>*priv)
>>>>> +{
>>>>> +     int ret;
>>>>> +     const char * const *cur = priv->triggers;
>>>>> +
>>>>> +     while (cur && *cur) {
>>>>> +             struct iio_trigger *trig;
>>>>> +
>>>>> +             trig = devm_iio_trigger_alloc(priv->dev, "%s",
>*cur);
>>>>> +             if  (!trig)
>>>>> +                     return -ENOMEM;
>>>>> +
>>>>> +             trig->dev.parent = priv->dev->parent;
>>>>> +             trig->ops = &timer_trigger_ops;
>>>>> +             trig->dev.groups = stm32_trigger_attr_groups;
>>>>> +             iio_trigger_set_drvdata(trig, priv);
>>>>> +
>>>>> +             ret = devm_iio_trigger_register(priv->dev, trig);
>>>>> +             if (ret)
>>>>> +                     return ret;
>>>>> +             cur++;
>>>>> +     }
>>>>> +
>>>>> +     return 0;
>>>>> +}
>>>>> +
>>>>> +/**
>>>>> + * is_stm32_timer_trigger
>>>>> + * @trig: trigger to be checked
>>>>> + *
>>>>> + * return true if the trigger is a valid stm32 iio timer trigger
>>>>> + * either return false
>>>>> + */
>>>>> +bool is_stm32_timer_trigger(struct iio_trigger *trig)
>>>>> +{
>>>>> +     return (trig->ops == &timer_trigger_ops);
>>>>> +}
>>>>> +EXPORT_SYMBOL(is_stm32_timer_trigger);
>>>>> +
>>>>> +static int stm32_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_validate_trigger,
>>>>> +     .attrs = &stm32_timer_attr_group,
>>>>> +};
>>>>> +
>>>>> +static struct stm32_timer_trigger *stm32_setup_iio_device(struct
>device *dev)
>>>>> +{
>>>>> +     struct iio_dev *indio_dev;
>>>>> +     int ret;
>>>>> +
>>>>> +     indio_dev = devm_iio_device_alloc(dev,
>>>>> +                                       sizeof(struct
>stm32_timer_trigger));
>>>>> +     if (!indio_dev)
>>>>> +             return NULL;
>>>>> +
>>>>> +     indio_dev->name = dev_name(dev);
>>>>> +     indio_dev->dev.parent = dev;
>>>>> +     indio_dev->info = &stm32_trigger_info;
>>>>> +     indio_dev->modes = INDIO_EVENT_TRIGGERED;
>>>>> +     indio_dev->num_channels = 0;
>>>>> +     indio_dev->dev.of_node = dev->of_node;
>>>>> +
>>>>> +     ret = devm_iio_device_register(dev, indio_dev);
>>>>> +     if (ret)
>>>>> +             return NULL;
>>>>> +
>>>>> +     return iio_priv(indio_dev);
>>>>> +}
>>>>> +
>>>>> +static int stm32_timer_trigger_probe(struct platform_device
>*pdev)
>>>>> +{
>>>>> +     struct device *dev = &pdev->dev;
>>>>> +     struct stm32_timer_trigger *priv;
>>>>> +     struct stm32_timers *ddata =
>dev_get_drvdata(pdev->dev.parent);
>>>>> +     unsigned int index;
>>>>> +     int ret;
>>>>> +
>>>>> +     if (of_property_read_u32(dev->of_node, "reg", &index))
>>>>> +             return -EINVAL;
>>>>> +
>>>>> +     if (index >= ARRAY_SIZE(triggers_table))
>>>>> +             return -EINVAL;
>>>>> +
>>>>> +     /* Create an IIO device only if we have triggers to be
>validated */
>>>>> +     if (*valids_table[index])
>>>>> +             priv = stm32_setup_iio_device(dev);
>>>>
>>>> I still don't like this. Really feels like we shouldn't be creating
>an
>>>> iio device with all the bagage that carries just to allow us to do
>the
>>>> trigger trees.  We ought to have a much more light weight solution
>for this
>>>> functionality - we aren't typically even using the interrupt tree
>stuff
>>>> that the triggers for devices are all really about.
>>>>
>>>> A simpler approach of allowing each trigger the option of a parent
>seems like
>>>> it would be cleaner.  Could be done entirely within this driver in
>the first
>>>> instance.  Basically it would just look like your master and slave
>attributes
>>>> but have those under triggerX not iio:deviceX.
>>>>
>>>> We can work out how to make it more generic later - including
>perhaps the
>>>> option to trigger from triggers outside this driver, using some
>parallel
>>>> infrastructure to the device triggering.
>>>>
>>>>
>>>>> +     else
>>>>> +             priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>>>>> +
>>>>> +     if (!priv)
>>>>> +             return -ENOMEM;
>>>>> +
>>>>> +     priv->dev = dev;
>>>>> +     priv->regmap = ddata->regmap;
>>>>> +     priv->clk = ddata->clk;
>>>>> +     priv->max_arr = ddata->max_arr;
>>>>> +     priv->triggers = triggers_table[index];
>>>>> +     priv->valids = valids_table[index];
>>>>> +
>>>>> +     ret = stm32_setup_iio_triggers(priv);
>>>>> +     if (ret)
>>>>> +             return ret;
>>>>> +
>>>>> +     platform_set_drvdata(pdev, priv);
>>>>> +
>>>>> +     return 0;
>>>>> +}
>>>>> +
>>>>> +static const struct of_device_id stm32_trig_of_match[] = {
>>>>> +     { .compatible = "st,stm32-timer-trigger", },
>>>>> +     { /* end node */ },
>>>>> +};
>>>>> +MODULE_DEVICE_TABLE(of, stm32_trig_of_match);
>>>>> +
>>>>> +static struct platform_driver stm32_timer_trigger_driver = {
>>>>> +     .probe = stm32_timer_trigger_probe,
>>>>> +     .driver = {
>>>>> +             .name = "stm32-timer-trigger",
>>>>> +             .of_match_table = stm32_trig_of_match,
>>>>> +     },
>>>>> +};
>>>>> +module_platform_driver(stm32_timer_trigger_driver);
>>>>> +
>>>>> +MODULE_ALIAS("platform: stm32-timer-trigger");
>>>>> +MODULE_DESCRIPTION("STMicroelectronics STM32 Timer Trigger
>driver");
>>>>> +MODULE_LICENSE("GPL v2");
>>>>> diff --git a/drivers/iio/trigger/Kconfig
>b/drivers/iio/trigger/Kconfig
>>>>> index 809b2e7..f2af4fe 100644
>>>>> --- a/drivers/iio/trigger/Kconfig
>>>>> +++ b/drivers/iio/trigger/Kconfig
>>>>> @@ -46,5 +46,4 @@ config IIO_SYSFS_TRIGGER
>>>>>
>>>>>         To compile this driver as a module, choose M here: the
>>>>>         module will be called iio-trig-sysfs.
>>>>> -
>>>> Clean this up.
>>>
>>> ok
>>>
>>>>>  endmenu
>>>>> diff --git a/include/linux/iio/timer/stm32-timer-trigger.h
>b/include/linux/iio/timer/stm32-timer-trigger.h
>>>>> new file mode 100644
>>>>> index 0000000..55535ae
>>>>> --- /dev/null
>>>>> +++ b/include/linux/iio/timer/stm32-timer-trigger.h
>>>>> @@ -0,0 +1,62 @@
>>>>> +/*
>>>>> + * Copyright (C) STMicroelectronics 2016
>>>>> + *
>>>>> + * Author: Benjamin Gaignard <benjamin.gaignard at st.com>
>>>>> + *
>>>>> + * License terms:  GNU General Public License (GPL), version 2
>>>>> + */
>>>>> +
>>>>> +#ifndef _STM32_TIMER_TRIGGER_H_
>>>>> +#define _STM32_TIMER_TRIGGER_H_
>>>>> +
>>>>> +#define TIM1_TRGO    "tim1_trgo"
>>>>> +#define TIM1_CH1     "tim1_ch1"
>>>>> +#define TIM1_CH2     "tim1_ch2"
>>>>> +#define TIM1_CH3     "tim1_ch3"
>>>>> +#define TIM1_CH4     "tim1_ch4"
>>>>> +
>>>>> +#define TIM2_TRGO    "tim2_trgo"
>>>>> +#define TIM2_CH1     "tim2_ch1"
>>>>> +#define TIM2_CH2     "tim2_ch2"
>>>>> +#define TIM2_CH3     "tim2_ch3"
>>>>> +#define TIM2_CH4     "tim2_ch4"
>>>>> +
>>>>> +#define TIM3_TRGO    "tim3_trgo"
>>>>> +#define TIM3_CH1     "tim3_ch1"
>>>>> +#define TIM3_CH2     "tim3_ch2"
>>>>> +#define TIM3_CH3     "tim3_ch3"
>>>>> +#define TIM3_CH4     "tim3_ch4"
>>>>> +
>>>>> +#define TIM4_TRGO    "tim4_trgo"
>>>>> +#define TIM4_CH1     "tim4_ch1"
>>>>> +#define TIM4_CH2     "tim4_ch2"
>>>>> +#define TIM4_CH3     "tim4_ch3"
>>>>> +#define TIM4_CH4     "tim4_ch4"
>>>>> +
>>>>> +#define TIM5_TRGO    "tim5_trgo"
>>>>> +#define TIM5_CH1     "tim5_ch1"
>>>>> +#define TIM5_CH2     "tim5_ch2"
>>>>> +#define TIM5_CH3     "tim5_ch3"
>>>>> +#define TIM5_CH4     "tim5_ch4"
>>>>> +
>>>>> +#define TIM6_TRGO    "tim6_trgo"
>>>>> +
>>>>> +#define TIM7_TRGO    "tim7_trgo"
>>>>> +
>>>>> +#define TIM8_TRGO    "tim8_trgo"
>>>>> +#define TIM8_CH1     "tim8_ch1"
>>>>> +#define TIM8_CH2     "tim8_ch2"
>>>>> +#define TIM8_CH3     "tim8_ch3"
>>>>> +#define TIM8_CH4     "tim8_ch4"
>>>>> +
>>>>> +#define TIM9_TRGO    "tim9_trgo"
>>>>> +#define TIM9_CH1     "tim9_ch1"
>>>>> +#define TIM9_CH2     "tim9_ch2"
>>>>> +
>>>>> +#define TIM12_TRGO   "tim12_trgo"
>>>>> +#define TIM12_CH1    "tim12_ch1"
>>>>> +#define TIM12_CH2    "tim12_ch2"
>>>>> +
>>>>> +bool is_stm32_timer_trigger(struct iio_trigger *trig);
>>>>> +
>>>>> +#endif
>>>>>
>>>>
>>>
>>>
>>>
>>

-- 
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