Re: [PATCH v2 1/2] iio: stm32 trigger: Add quadrature encoder device

From: Jonathan Cameron
Date: Sat Mar 25 2017 - 14:26:36 EST

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In reply to: Benjamin Gaignard: "[PATCH v2 1/2] iio: stm32 trigger: Add quadrature encoder device"
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On 24/03/17 14:00, 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@xxxxxx>
A few little nitpicks.

Otherwise I like this. Would love William to give another review
though if he has time.

I've tacked Michael Welling on the cc list as well as he has offered
to help the beaglebone lot upstream some drivers, including the
eqep quadrature encoder drivers - so he can poke the right people
to get some review of the ABI from their point of view as well.

Thanks

Jonathan
> ---
> .../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..fbdee4f 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@xxxxxx
> +Description:
> + Reading returns the current preset value.
> + Writing set the preset value.
> + When counting up the counter start from 0 and fire an event when reach preset value.
> + When counting down the counter start from preset value and fire event when reach 0.
We'll want to generalize that description at some point as it's most often used as a place to reset
too on an event (homing switch or similar)
> +
> +What: /sys/bus/iio/devices/iio:deviceX/in_count_quadrature_mode_available
> +KernelVersion: 4.12
> +Contact: benjamin.gaignard@xxxxxx
> +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@xxxxxx
> +Description:
> + Configure the device counter quadrature modes:
> + channel_A:
> + Encoder A input severs as the count input and B as
> + the UP/DOWN direction control input.
> +
> + channel_B:
> + Encoder B input severs 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.
Whilst the quadrature mode is always with that scale on this device, we should
as discussed be explicitly providing access to the scale so that we can
cope with different scales on different devices. As such the docs here
shouldn't mention it.

I'm keen to get these docs straight into sysfs-bus-iio or perhaps
sysfs-bus-iio-encoder-counter asap so good to write them with that at the
front of your mind.

> diff --git a/drivers/iio/trigger/stm32-timer-trigger.c b/drivers/iio/trigger/stm32-timer-trigger.c
> index 994b96d..48d2bf9 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_trigger_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
I really don't like the naming as trigger_read_raw. Lets just
call it counter_read_raw and then it 'feels' much nicer ;)

The driver is becoming a two part one with a trigger and a counter
driver (and links between them). Lets let the naming reflect that.
> +{
> + 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;
> +
> + /* return scale only if quadrature mode is selected */
> + if (smcr != 3)
> + return -EINVAL;
Why not return a scale of unity rather than an error? (which will confuse
users).
> +
> + /* fixed scale */
> + *val = 1;
> + *val2 = 2;
> + return IIO_VAL_FRACTIONAL_LOG2;
> + }
> + }
> +
> + return -EINVAL;
> +}
> +
> +static int stm32_trigger_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_trigger_read_raw,
> + .write_raw = stm32_trigger_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_iio_device(struct device *dev)
That wins the slightly overly generic name! There are several other
stm32 iio devices already. setup_counter_device maybe?
> +{
> + 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_iio_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 */
>

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