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Date:   Sun, 2 Apr 2017 12:02:28 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     William Breathitt Gray <vilhelm.gray@...il.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>
Cc:     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 v3 1/2] iio: stm32 trigger: Add quadrature encoder device

On 27/03/17 15:23, William Breathitt Gray wrote:
> On Mon, Mar 27, 2017 at 04:14:25PM +0200, Benjamin Gaignard wrote:
>> 2017-03-27 15:47 GMT+02:00 William Breathitt Gray <vilhelm.gray@...il.com>:
>>> On Mon, Mar 27, 2017 at 11:43:23AM +0200, Benjamin Gaignard wrote:
>>>> One of the features of STM32 trigger hardware block is a quadrature
>>>> encoder that can counts up/down depending of the levels and edges
>>>> of the selected external pins.
>>>>
>>>> This patch allow to read/write the counter, get it direction,
>>>> set/get quadrature modes and get scale factor.
>>>>
>>>> When counting up preset value is the limit of the counter.
>>>> When counting down the counter start from preset value down to 0.
>>>> This preset value could be set/get by using
>>>> /sys/bus/iio/devices/iio:deviceX/in_count0_preset attribute.
>>>>
>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...com>
>>>
>>> Hi Benjamin,
>>>
>>> This is pretty close to the ABI I had in mind. I'm a bit confused about
>>> how to select some of functionality we discussed in the previous version
>>> so I'll write those comments inline. Overall nice work! :)
>>>
>>>>
>>>> version 3:
>>>> - fix typo in documentation
>>>> - change some functions names
>>>> ---
>>>> .../ABI/testing/sysfs-bus-iio-timer-stm32          |  32 +++
>>>> drivers/iio/trigger/stm32-timer-trigger.c          | 244 ++++++++++++++++++++-
>>>> include/linux/mfd/stm32-timers.h                   |   2 +
>>>> 3 files changed, 272 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32 b/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>>>> index 6534a60..bf795ad 100644
>>>> --- a/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>>>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-timer-stm32
>>>> @@ -27,3 +27,35 @@ Description:
>>>>               Reading returns the current sampling frequency.
>>>>               Writing an value different of 0 set and start sampling.
>>>>               Writing 0 stop sampling.
>>>> +
>>>> +What:         /sys/bus/iio/devices/iio:deviceX/in_count0_preset
>>>> +KernelVersion:        4.12
>>>> +Contact:      benjamin.gaignard@...com
>>>> +Description:
>>>> +              Reading returns the current preset value.
>>>> +              Writing sets the preset value.
>>>> +              When counting up the counter starts from 0 and fires an event when reach preset value.
>>>> +              When counting down the counter start from preset value and fire event when reach 0.
>>>
>>> In one of the previous versions we discussed a "reset" mode of operation
>>> where the counter would be reset to the preset value on the rising edge
>>> of pin 1. How would a user select this mode of operation using this ABI
>>> (I assume the preset value would be the same value as in the
>>> in_count0_preset attribute).
>>>
>>> Also, would this "reset" mode be limited to count just the internal
>>> clock, or may an external pin alternatively serve as a counter source?
>>
>> In reset mode counter is clocked by the internal clock
>> Reset can only by drive by a rising edge of an internal signal
>> (represented by an IIO trigger).
> 
> Ah, my apologies, I was under the incorrect impression that the reset
> trigger was an external signal. I think understand how it works now.
That's certainly going to be an option on the 'general' form of this
ABI.  We can generalize at that point to cover it I think.
> 
>>
>>>
>>>> +
>>>> +What:         /sys/bus/iio/devices/iio:deviceX/in_count_quadrature_mode_available
>>>> +KernelVersion:        4.12
>>>> +Contact:      benjamin.gaignard@...com
>>>> +Description:
>>>> +              Reading returns the list possible quadrature modes.
>>>> +
>>>> +What:         /sys/bus/iio/devices/iio:deviceX/in_count0_quadrature_mode
>>>> +KernelVersion:        4.12
>>>> +Contact:      benjamin.gaignard@...com
>>>> +Description:
>>>> +              Configure the device counter quadrature modes:
>>>> +              channel_A:
>>>> +                      Encoder A input servers as the count input and B as
>>>> +                      the UP/DOWN direction control input.
>>>> +
>>>> +              channel_B:
>>>> +                      Encoder B input serves as the count input and A as
>>>> +                      the UP/DOWN direction control input.
>>>> +
>>>> +              quadrature:
>>>> +                      Encoder A and B inputs are mixed to get direction
>>>> +                      and count with a scale of 0.25.
>>>
>>> If I want to select the internal clock as the counter source, how would
>>> I do so? Should there be an "internal_clock" mode available in the
>>> quadrature_mode attribute?
>>
>> To use internal clock as counter source you must select one of the modes
>> in in_count0_enable_mode attribute (patch 2/2)
>>
>> Counter could be drived by 3 "sources": internal clock, encoder input
>> and internal signal
>> I have in mind to keep this split in 3 attributes:enable_mode,
>> quadrature_mode and a futur
>> trigger_mode.
> 
> Many thanks for the further explanation. This clears up my confusion,
> and I believe the interaction between these 3 attributes should work out
> quite well for future drivers too.
> 
> William Breathitt Gray
> 
>>
>>
>>>
>>> Sincerely,
>>>
>>> William Breathitt Gray
>>>
>>>> diff --git a/drivers/iio/trigger/stm32-timer-trigger.c b/drivers/iio/trigger/stm32-timer-trigger.c
>>>> index 994b96d..7db904c 100644
>>>> --- a/drivers/iio/trigger/stm32-timer-trigger.c
>>>> +++ b/drivers/iio/trigger/stm32-timer-trigger.c
>>>> @@ -15,6 +15,7 @@
>>>> #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] = {
>>>> @@ -32,12 +33,29 @@
>>>>       { TIM12_TRGO, TIM12_CH1, TIM12_CH2,},
>>>> };
>>>>
>>>> +/* List the triggers accepted by each timer */
>>>> +static const void *valids_table[][MAX_VALIDS] = {
>>>> +      { TIM5_TRGO, TIM2_TRGO, TIM3_TRGO, TIM4_TRGO,},
>>>> +      { TIM1_TRGO, TIM8_TRGO, TIM3_TRGO, TIM4_TRGO,},
>>>> +      { TIM1_TRGO, TIM2_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,},
>>>> +      { }, /* timer 10 */
>>>> +      { }, /* timer 11 */
>>>> +      { 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,
>>>> @@ -180,8 +198,7 @@ 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);
>>>> +      struct stm32_timer_trigger *priv = dev_get_drvdata(dev);
>>>>       u32 cr2;
>>>>
>>>>       regmap_read(priv->regmap, TIM_CR2, &cr2);
>>>> @@ -194,8 +211,7 @@ 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);
>>>> +      struct stm32_timer_trigger *priv = dev_get_drvdata(dev);
>>>>       int i;
>>>>
>>>>       for (i = 0; i < ARRAY_SIZE(master_mode_table); i++) {
>>>> @@ -275,6 +291,216 @@ static int stm32_setup_iio_triggers(struct stm32_timer_trigger *priv)
>>>>       return 0;
>>>> }
>>>>
>>>> +static int stm32_counter_read_raw(struct iio_dev *indio_dev,
>>>> +                                struct iio_chan_spec const *chan,
>>>> +                                int *val, int *val2, long mask)
>>>> +{
>>>> +      struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>> +
>>>> +      switch (mask) {
>>>> +      case IIO_CHAN_INFO_RAW:
>>>> +      {
>>>> +              u32 cnt;
>>>> +
>>>> +              regmap_read(priv->regmap, TIM_CNT, &cnt);
>>>> +              *val = cnt;
>>>> +
>>>> +              return IIO_VAL_INT;
>>>> +      }
>>>> +      case IIO_CHAN_INFO_SCALE:
>>>> +      {
>>>> +              u32 smcr;
>>>> +
>>>> +              regmap_read(priv->regmap, TIM_SMCR, &smcr);
>>>> +              smcr &= TIM_SMCR_SMS;
>>>> +
>>>> +              *val = 1;
>>>> +              *val2 = 0;
>>>> +
>>>> +              /* in quadrature case scale = 0.25 */
>>>> +              if (smcr == 3)
>>>> +                      *val2 = 2;
>>>> +
>>>> +              return IIO_VAL_FRACTIONAL_LOG2;
>>>> +      }
>>>> +      }
>>>> +
>>>> +      return -EINVAL;
>>>> +}
>>>> +
>>>> +static int stm32_counter_write_raw(struct iio_dev *indio_dev,
>>>> +                                 struct iio_chan_spec const *chan,
>>>> +                                 int val, int val2, long mask)
>>>> +{
>>>> +      struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>> +
>>>> +      switch (mask) {
>>>> +      case IIO_CHAN_INFO_RAW:
>>>> +              regmap_write(priv->regmap, TIM_CNT, val);
>>>> +
>>>> +              return IIO_VAL_INT;
>>>> +      case IIO_CHAN_INFO_SCALE:
>>>> +              /* fixed scale */
>>>> +              return -EINVAL;
>>>> +      }
>>>> +
>>>> +      return -EINVAL;
>>>> +}
>>>> +
>>>> +static const struct iio_info stm32_trigger_info = {
>>>> +      .driver_module = THIS_MODULE,
>>>> +      .read_raw = stm32_counter_read_raw,
>>>> +      .write_raw = stm32_counter_write_raw
>>>> +};
>>>> +
>>>> +static const char *const stm32_quadrature_modes[] = {
>>>> +      "channel_A",
>>>> +      "channel_B",
>>>> +      "quadrature",
>>>> +};
>>>> +
>>>> +static int stm32_set_quadrature_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, mode + 1);
>>>> +
>>>> +      return 0;
>>>> +}
>>>> +
>>>> +static int stm32_get_quadrature_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);
>>>> +      smcr &= TIM_SMCR_SMS;
>>>> +
>>>> +      return smcr - 1;
>>>> +}
>>>> +
>>>> +static const struct iio_enum stm32_quadrature_mode_enum = {
>>>> +      .items = stm32_quadrature_modes,
>>>> +      .num_items = ARRAY_SIZE(stm32_quadrature_modes),
>>>> +      .set = stm32_set_quadrature_mode,
>>>> +      .get = stm32_get_quadrature_mode
>>>> +};
>>>> +
>>>> +static const char *const stm32_count_direction_states[] = {
>>>> +      "up",
>>>> +      "down"
>>>> +};
>>>> +
>>>> +static int stm32_set_count_direction(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_CR1, TIM_CR1_DIR, mode);
>>>> +
>>>> +      return 0;
>>>> +}
>>>> +
>>>> +static int stm32_get_count_direction(struct iio_dev *indio_dev,
>>>> +                                   const struct iio_chan_spec *chan)
>>>> +{
>>>> +      struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>> +      u32 cr1;
>>>> +
>>>> +      regmap_read(priv->regmap, TIM_CR1, &cr1);
>>>> +
>>>> +      return (cr1 & TIM_CR1_DIR);
>>>> +}
>>>> +
>>>> +static const struct iio_enum stm32_count_direction_enum = {
>>>> +      .items = stm32_count_direction_states,
>>>> +      .num_items = ARRAY_SIZE(stm32_count_direction_states),
>>>> +      .set = stm32_set_count_direction,
>>>> +      .get = stm32_get_count_direction
>>>> +};
>>>> +
>>>> +static ssize_t stm32_count_get_preset(struct iio_dev *indio_dev,
>>>> +                                    uintptr_t private,
>>>> +                                    const struct iio_chan_spec *chan,
>>>> +                                    char *buf)
>>>> +{
>>>> +      struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>> +      u32 arr;
>>>> +
>>>> +      regmap_read(priv->regmap, TIM_ARR, &arr);
>>>> +
>>>> +      return snprintf(buf, PAGE_SIZE, "%u\n", arr);
>>>> +}
>>>> +
>>>> +static ssize_t stm32_count_set_preset(struct iio_dev *indio_dev,
>>>> +                                    uintptr_t private,
>>>> +                                    const struct iio_chan_spec *chan,
>>>> +                                    const char *buf, size_t len)
>>>> +{
>>>> +      struct stm32_timer_trigger *priv = iio_priv(indio_dev);
>>>> +      unsigned int preset;
>>>> +      int ret;
>>>> +
>>>> +      ret = kstrtouint(buf, 0, &preset);
>>>> +      if (ret)
>>>> +              return ret;
>>>> +
>>>> +      regmap_write(priv->regmap, TIM_ARR, preset);
>>>> +      regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, TIM_CR1_ARPE);
>>>> +
>>>> +      return len;
>>>> +}
>>>> +
>>>> +static const struct iio_chan_spec_ext_info stm32_trigger_count_info[] = {
>>>> +      {
>>>> +              .name = "preset",
>>>> +              .shared = IIO_SEPARATE,
>>>> +              .read = stm32_count_get_preset,
>>>> +              .write = stm32_count_set_preset
>>>> +      },
>>>> +      IIO_ENUM("count_direction", IIO_SEPARATE, &stm32_count_direction_enum),
>>>> +      IIO_ENUM_AVAILABLE("count_direction", &stm32_count_direction_enum),
>>>> +      IIO_ENUM("quadrature_mode", IIO_SEPARATE, &stm32_quadrature_mode_enum),
>>>> +      IIO_ENUM_AVAILABLE("quadrature_mode", &stm32_quadrature_mode_enum),
>>>> +      {}
>>>> +};
>>>> +
>>>> +static const struct iio_chan_spec stm32_trigger_channel = {
>>>> +      .type = IIO_COUNT,
>>>> +      .channel = 0,
>>>> +      .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
>>>> +      .ext_info = stm32_trigger_count_info,
>>>> +      .indexed = 1
>>>> +};
>>>> +
>>>> +static struct stm32_timer_trigger *stm32_setup_counter_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->num_channels = 1;
>>>> +      indio_dev->channels = &stm32_trigger_channel;
>>>> +      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);
>>>> +}
>>>> +
>>>> /**
>>>>  * is_stm32_timer_trigger
>>>>  * @trig: trigger to be checked
>>>> @@ -299,10 +525,15 @@ static int stm32_timer_trigger_probe(struct platform_device *pdev)
>>>>       if (of_property_read_u32(dev->of_node, "reg", &index))
>>>>               return -EINVAL;
>>>>
>>>> -      if (index >= ARRAY_SIZE(triggers_table))
>>>> +      if (index >= ARRAY_SIZE(triggers_table) ||
>>>> +          index >= ARRAY_SIZE(valids_table))
>>>>               return -EINVAL;
>>>>
>>>> -      priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>>>> +      /* Create an IIO device only if we have triggers to be validated */
>>>> +      if (*valids_table[index])
>>>> +              priv = stm32_setup_counter_device(dev);
>>>> +      else
>>>> +              priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>>>>
>>>>       if (!priv)
>>>>               return -ENOMEM;
>>>> @@ -312,6 +543,7 @@ static int stm32_timer_trigger_probe(struct platform_device *pdev)
>>>>       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)
>>>> diff --git a/include/linux/mfd/stm32-timers.h b/include/linux/mfd/stm32-timers.h
>>>> index d030004..4a0abbc 100644
>>>> --- a/include/linux/mfd/stm32-timers.h
>>>> +++ b/include/linux/mfd/stm32-timers.h
>>>> @@ -21,6 +21,7 @@
>>>> #define TIM_CCMR1     0x18    /* Capt/Comp 1 Mode Reg    */
>>>> #define TIM_CCMR2     0x1C    /* Capt/Comp 2 Mode Reg    */
>>>> #define TIM_CCER      0x20    /* Capt/Comp Enable Reg    */
>>>> +#define TIM_CNT               0x24    /* Counter                 */
>>>> #define TIM_PSC               0x28    /* Prescaler               */
>>>> #define TIM_ARR               0x2c    /* Auto-Reload Register    */
>>>> #define TIM_CCR1      0x34    /* Capt/Comp Register 1    */
>>>> @@ -30,6 +31,7 @@
>>>> #define TIM_BDTR      0x44    /* Break and Dead-Time Reg */
>>>>
>>>> #define TIM_CR1_CEN   BIT(0)  /* Counter Enable          */
>>>> +#define TIM_CR1_DIR   BIT(4)  /* Counter Direction       */
>>>> #define TIM_CR1_ARPE  BIT(7)  /* Auto-reload Preload Ena */
>>>> #define TIM_CR2_MMS   (BIT(4) | BIT(5) | BIT(6)) /* Master mode selection */
>>>> #define TIM_SMCR_SMS  (BIT(0) | BIT(1) | BIT(2)) /* Slave mode selection */
>>>> --
>>>> 1.9.1
>>>>
>>
>>
>>
>> -- 
>> Benjamin Gaignard
>>
>> Graphic Study Group
>>
>> Linaro.org │ Open source software for ARM SoCs
>>
>> Follow Linaro: Facebook | Twitter | Blog
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