iio: stm32 trigger: Add counter enable modes

Device counting could be controlled by the level or the edges of
a trigger.
in_count0_enable_mode attibute allow to set the control mode.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

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

@@ -65,3 +65,28 @@ Description:
 		quadrature:
 			Encoder A and B inputs are mixed to get direction
 			and count with a scale of 0.25.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_count_enable_mode_available
+KernelVersion:	4.12
+Contact:	benjamin.gaignard@st.com
+Description:
+		Reading returns the list possible enable modes.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_count0_enable_mode
+KernelVersion:	4.12
+Contact:	benjamin.gaignard@st.com
+Description:
+		Configure the device counter enable modes, in all case
+		counting direction is set by in_count0_count_direction
+		attribute and the counter is clocked by the internal clock.
+		always:
+			Counter is always ON.
+
+		gated:
+			Counting is enabled when connected trigger signal
+			level is high else counting is disabled.
+
+		triggered:
+			Counting is enabled on rising edge of the connected
+			trigger, and remains enabled for the duration of this
+			selected mode.

drivers/iio/trigger/stm32-timer-trigger.c

@@ -353,6 +353,74 @@ static const struct iio_info stm32_trigger_info = {
 	.write_raw = stm32_counter_write_raw
 };
 
+static const char *const stm32_enable_modes[] = {
+	"always",
+	"gated",
+	"triggered",
+};
+
+static int stm32_enable_mode2sms(int mode)
+{
+	switch (mode) {
+	case 0:
+		return 0;
+	case 1:
+		return 5;
+	case 2:
+		return 6;
+	}
+
+	return -EINVAL;
+}
+
+static int stm32_set_enable_mode(struct iio_dev *indio_dev,
+				 const struct iio_chan_spec *chan,
+				 unsigned int mode)
+{
+	struct stm32_timer_trigger *priv = iio_priv(indio_dev);
+	int sms = stm32_enable_mode2sms(mode);
+
+	if (sms < 0)
+		return sms;
+
+	regmap_update_bits(priv->regmap, TIM_SMCR, TIM_SMCR_SMS, sms);
+
+	return 0;
+}
+
+static int stm32_sms2enable_mode(int mode)
+{
+	switch (mode) {
+	case 0:
+		return 0;
+	case 5:
+		return 1;
+	case 6:
+		return 2;
+	}
+
+	return -EINVAL;
+}
+
+static int stm32_get_enable_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 stm32_sms2enable_mode(smcr);
+}
+
+static const struct iio_enum stm32_enable_mode_enum = {
+	.items = stm32_enable_modes,
+	.num_items = ARRAY_SIZE(stm32_enable_modes),
+	.set = stm32_set_enable_mode,
+	.get = stm32_get_enable_mode
+};
+
 static const char *const stm32_quadrature_modes[] = {
 	"channel_A",
 	"channel_B",
@@ -466,6 +534,8 @@ static const struct iio_chan_spec_ext_info stm32_trigger_count_info[] = {
 	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),
+	IIO_ENUM("enable_mode", IIO_SEPARATE, &stm32_enable_mode_enum),
+	IIO_ENUM_AVAILABLE("enable_mode", &stm32_enable_mode_enum),
 	{}
 };