Re: [PATCH v3 1/2] iio: stm32 trigger: Add quadrature encoder device

From: William Breathitt Gray
Date: Mon Mar 27 2017 - 10:07:48 EST

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In reply to: Benjamin Gaignard: "[PATCH v3 1/2] iio: stm32 trigger: Add quadrature encoder device"
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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@xxxxxx>

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@xxxxxx
>+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?

>+
>+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 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?

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
>

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