[PATCH v2 4/5] iio: dac: stm32: add support for trigger events

[Fabrice Gasnier]

STM32 DAC supports triggers to synchronize conversions. When trigger
occurs, data is transferred from DHR (data holding register) to DOR
(data output register) so output voltage is updated.
Both hardware and software triggers are supported.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
---
Changes in v2:
- Fix issue with trigger, by using set_trigger callback
- trigger can now be assigned, no matters powerdown state
---
 drivers/iio/dac/Kconfig          |   3 +
 drivers/iio/dac/stm32-dac-core.h |   8 +++
 drivers/iio/dac/stm32-dac.c      | 127 ++++++++++++++++++++++++++++++++++++++-
 3 files changed, 137 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 7198648..786c38b 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -278,6 +278,9 @@ config STM32_DAC
 	tristate "STMicroelectronics STM32 DAC"
 	depends on (ARCH_STM32 && OF) || COMPILE_TEST
 	depends on REGULATOR
+	select IIO_TRIGGERED_EVENT
+	select IIO_STM32_TIMER_TRIGGER
+	select MFD_STM32_TIMERS
 	select STM32_DAC_CORE
 	help
 	  Say yes here to build support for STMicroelectronics STM32 Digital
diff --git a/drivers/iio/dac/stm32-dac-core.h b/drivers/iio/dac/stm32-dac-core.h
index daf0993..e51a468 100644
--- a/drivers/iio/dac/stm32-dac-core.h
+++ b/drivers/iio/dac/stm32-dac-core.h
@@ -26,6 +26,7 @@
 
 /* STM32 DAC registers */
 #define STM32_DAC_CR		0x00
+#define STM32_DAC_SWTRIGR	0x04
 #define STM32_DAC_DHR12R1	0x08
 #define STM32_DAC_DHR12R2	0x14
 #define STM32_DAC_DOR1		0x2C
@@ -33,9 +34,16 @@
 
 /* STM32_DAC_CR bit fields */
 #define STM32_DAC_CR_EN1		BIT(0)
+#define STM32H7_DAC_CR_TEN1		BIT(1)
+#define STM32H7_DAC_CR_TSEL1_SHIFT	2
+#define STM32H7_DAC_CR_TSEL1		GENMASK(5, 2)
 #define STM32H7_DAC_CR_HFSEL		BIT(15)
 #define STM32_DAC_CR_EN2		BIT(16)
 
+/* STM32_DAC_SWTRIGR bit fields */
+#define STM32_DAC_SWTRIGR_SWTRIG1	BIT(0)
+#define STM32_DAC_SWTRIGR_SWTRIG2	BIT(1)
+
 /**
  * struct stm32_dac_common - stm32 DAC driver common data (for all instances)
  * @regmap: DAC registers shared via regmap
diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
index c0d993a..a7a078e 100644
--- a/drivers/iio/dac/stm32-dac.c
+++ b/drivers/iio/dac/stm32-dac.c
@@ -23,6 +23,10 @@
 #include <linux/bitfield.h>
 #include <linux/delay.h>
 #include <linux/iio/iio.h>
+#include <linux/iio/timer/stm32-timer-trigger.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_event.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -32,15 +36,113 @@
 #define STM32_DAC_CHANNEL_1		1
 #define STM32_DAC_CHANNEL_2		2
 #define STM32_DAC_IS_CHAN_1(ch)		((ch) & STM32_DAC_CHANNEL_1)
+/* channel2 shift */
+#define STM32_DAC_CHAN2_SHIFT		16
 
 /**
  * struct stm32_dac - private data of DAC driver
  * @common:		reference to DAC common data
+ * @swtrig:		Using software trigger
  */
 struct stm32_dac {
 	struct stm32_dac_common *common;
+	bool swtrig;
 };
 
+/**
+ * struct stm32_dac_trig_info - DAC trigger info
+ * @name: name of the trigger, corresponding to its source
+ * @tsel: trigger selection, value to be configured in DAC_CR.TSELx
+ */
+struct stm32_dac_trig_info {
+	const char *name;
+	u32 tsel;
+};
+
+static const struct stm32_dac_trig_info stm32h7_dac_trinfo[] = {
+	{ "swtrig", 0 },
+	{ TIM1_TRGO, 1 },
+	{ TIM2_TRGO, 2 },
+	{ TIM4_TRGO, 3 },
+	{ TIM5_TRGO, 4 },
+	{ TIM6_TRGO, 5 },
+	{ TIM7_TRGO, 6 },
+	{ TIM8_TRGO, 7 },
+	{},
+};
+
+static irqreturn_t stm32_dac_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct stm32_dac *dac = iio_priv(indio_dev);
+	int channel = indio_dev->channels[0].channel;
+
+	/* Using software trigger? Then, trigger it now */
+	if (dac->swtrig) {
+		u32 swtrig;
+
+		if (STM32_DAC_IS_CHAN_1(channel))
+			swtrig = STM32_DAC_SWTRIGR_SWTRIG1;
+		else
+			swtrig = STM32_DAC_SWTRIGR_SWTRIG2;
+		regmap_update_bits(dac->common->regmap, STM32_DAC_SWTRIGR,
+				   swtrig, swtrig);
+	}
+
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static unsigned int stm32_dac_get_trig_tsel(struct stm32_dac *dac,
+					    struct iio_trigger *trig)
+{
+	unsigned int i;
+
+	/* skip 1st trigger that should be swtrig */
+	for (i = 1; stm32h7_dac_trinfo[i].name; i++) {
+		/*
+		 * Checking both stm32 timer trigger type and trig name
+		 * should be safe against arbitrary trigger names.
+		 */
+		if (is_stm32_timer_trigger(trig) &&
+		    !strcmp(stm32h7_dac_trinfo[i].name, trig->name)) {
+			return stm32h7_dac_trinfo[i].tsel;
+		}
+	}
+
+	/* When no trigger has been found, default to software trigger */
+	dac->swtrig = true;
+
+	return stm32h7_dac_trinfo[0].tsel;
+}
+
+static int stm32_dac_set_trigger(struct iio_dev *indio_dev,
+				 struct iio_trigger *trig)
+{
+	struct stm32_dac *dac = iio_priv(indio_dev);
+	int channel = indio_dev->channels[0].channel;
+	u32 shift = STM32_DAC_IS_CHAN_1(channel) ? 0 : STM32_DAC_CHAN2_SHIFT;
+	u32 val = 0, tsel;
+	u32 msk = (STM32H7_DAC_CR_TEN1 | STM32H7_DAC_CR_TSEL1) << shift;
+
+	dac->swtrig = false;
+	if (trig) {
+		/* select & enable trigger (tsel / ten) */
+		tsel = stm32_dac_get_trig_tsel(dac, trig);
+		val = tsel << STM32H7_DAC_CR_TSEL1_SHIFT;
+		val = (val | STM32H7_DAC_CR_TEN1) << shift;
+	}
+
+	if (trig)
+		dev_dbg(&indio_dev->dev, "enable trigger: %s\n", trig->name);
+	else
+		dev_dbg(&indio_dev->dev, "disable trigger\n");
+
+	return regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, val);
+}
+
 static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
 {
 	struct stm32_dac *dac = iio_priv(indio_dev);
@@ -167,6 +269,7 @@ static int stm32_dac_debugfs_reg_access(struct iio_dev *indio_dev,
 static const struct iio_info stm32_dac_iio_info = {
 	.read_raw = stm32_dac_read_raw,
 	.write_raw = stm32_dac_write_raw,
+	.set_trigger = stm32_dac_set_trigger,
 	.debugfs_reg_access = stm32_dac_debugfs_reg_access,
 	.driver_module = THIS_MODULE,
 };
@@ -326,7 +429,28 @@ static int stm32_dac_probe(struct platform_device *pdev)
 	if (ret < 0)
 		return ret;
 
-	return devm_iio_device_register(&pdev->dev, indio_dev);
+	ret = iio_triggered_event_setup(indio_dev, NULL,
+					stm32_dac_trigger_handler);
+	if (ret)
+		return ret;
+
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		iio_triggered_event_cleanup(indio_dev);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int stm32_dac_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+
+	iio_triggered_event_cleanup(indio_dev);
+	iio_device_unregister(indio_dev);
+
+	return 0;
 }
 
 static const struct of_device_id stm32_dac_of_match[] = {
@@ -337,6 +461,7 @@ static int stm32_dac_probe(struct platform_device *pdev)
 
 static struct platform_driver stm32_dac_driver = {
 	.probe = stm32_dac_probe,
+	.remove = stm32_dac_remove,
 	.driver = {
 		.name = "stm32-dac",
 		.of_match_table = stm32_dac_of_match,
-- 
1.9.1