iio: stm32 trigger: Add quadrature encoder device

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@st.com>
Reviewed-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/ABI/testing/sysfs-bus-iio-timer-stm32

@@ -3,11 +3,15 @@ KernelVersion:	4.11
 Contact:	benjamin.gaignard@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.
+		- "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.
+				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.
@@ -27,3 +31,37 @@ 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@st.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.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_count_quadrature_mode_available
+KernelVersion:	4.12
+Contact:	benjamin.gaignard@st.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@st.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.

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 @@ static const void *triggers_table[][MAX_TRIGGERS] = {
 	{ 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)

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 */