iio: adc: stm32: add support for triggered buffer mode

STM32 ADC conversions can be launched using hardware triggers.
It can be used to start conversion sequences (group of channels).
Selected channels are select via sequence registers.
Trigger source is selected via 'extsel' (external trigger mux).
Trigger polarity is set to rising edge by default.
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/Kconfig

@@ -499,6 +499,8 @@ config STM32_ADC_CORE
 	depends on ARCH_STM32 || COMPILE_TEST
 	depends on OF
 	depends on REGULATOR
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
 	help
 	  Select this option to enable the core driver for STMicroelectronics
 	  STM32 analog-to-digital converter (ADC).

drivers/iio/adc/stm32-adc.c

@@ -22,6 +22,10 @@
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/module.h>
@@ -58,21 +62,37 @@
 
 /* STM32F4_ADC_CR2 - bit fields */
 #define STM32F4_SWSTART			BIT(30)
+#define STM32F4_EXTEN_SHIFT		28
 #define STM32F4_EXTEN_MASK		GENMASK(29, 28)
+#define STM32F4_EXTSEL_SHIFT		24
+#define STM32F4_EXTSEL_MASK		GENMASK(27, 24)
 #define STM32F4_EOCS			BIT(10)
 #define STM32F4_ADON			BIT(0)
 
-/* STM32F4_ADC_SQR1 - bit fields */
-#define STM32F4_L_SHIFT			20
-#define STM32F4_L_MASK			GENMASK(23, 20)
-
-/* STM32F4_ADC_SQR3 - bit fields */
-#define STM32F4_SQ1_SHIFT		0
-#define STM32F4_SQ1_MASK		GENMASK(4, 0)
-
+#define STM32_ADC_MAX_SQ		16	/* SQ1..SQ16 */
 #define STM32_ADC_TIMEOUT_US		100000
 #define STM32_ADC_TIMEOUT	(msecs_to_jiffies(STM32_ADC_TIMEOUT_US / 1000))
 
+/* External trigger enable */
+enum stm32_adc_exten {
+	STM32_EXTEN_SWTRIG,
+	STM32_EXTEN_HWTRIG_RISING_EDGE,
+	STM32_EXTEN_HWTRIG_FALLING_EDGE,
+	STM32_EXTEN_HWTRIG_BOTH_EDGES,
+};
+
+/**
+ * stm32_adc_regs - stm32 ADC misc registers & bitfield desc
+ * @reg:		register offset
+ * @mask:		bitfield mask
+ * @shift:		left shift
+ */
+struct stm32_adc_regs {
+	int reg;
+	int mask;
+	int shift;
+};
+
 /**
  * struct stm32_adc - private data of each ADC IIO instance
  * @common:		reference to ADC block common data
@@ -82,15 +102,19 @@
  * @clk:		clock for this adc instance
  * @irq:		interrupt for this adc instance
  * @lock:		spinlock
+ * @bufi:		data buffer index
+ * @num_conv:		expected number of scan conversions
  */
 struct stm32_adc {
 	struct stm32_adc_common	*common;
 	u32			offset;
 	struct completion	completion;
-	u16			*buffer;
+	u16			buffer[STM32_ADC_MAX_SQ];
 	struct clk		*clk;
 	int			irq;
 	spinlock_t		lock;		/* interrupt lock */
+	unsigned int		bufi;
+	unsigned int		num_conv;
 };
 
 /**
@@ -125,6 +149,33 @@ static const struct stm32_adc_chan_spec stm32f4_adc123_channels[] = {
 	{ IIO_VOLTAGE, 15, "in15" },
 };
 
+/**
+ * stm32f4_sq - describe regular sequence registers
+ * - L: sequence len (register & bit field)
+ * - SQ1..SQ16: sequence entries (register & bit field)
+ */
+static const struct stm32_adc_regs stm32f4_sq[STM32_ADC_MAX_SQ + 1] = {
+	/* L: len bit field description to be kept as first element */
+	{ STM32F4_ADC_SQR1, GENMASK(23, 20), 20 },
+	/* SQ1..SQ16 registers & bit fields (reg, mask, shift) */
+	{ STM32F4_ADC_SQR3, GENMASK(4, 0), 0 },
+	{ STM32F4_ADC_SQR3, GENMASK(9, 5), 5 },
+	{ STM32F4_ADC_SQR3, GENMASK(14, 10), 10 },
+	{ STM32F4_ADC_SQR3, GENMASK(19, 15), 15 },
+	{ STM32F4_ADC_SQR3, GENMASK(24, 20), 20 },
+	{ STM32F4_ADC_SQR3, GENMASK(29, 25), 25 },
+	{ STM32F4_ADC_SQR2, GENMASK(4, 0), 0 },
+	{ STM32F4_ADC_SQR2, GENMASK(9, 5), 5 },
+	{ STM32F4_ADC_SQR2, GENMASK(14, 10), 10 },
+	{ STM32F4_ADC_SQR2, GENMASK(19, 15), 15 },
+	{ STM32F4_ADC_SQR2, GENMASK(24, 20), 20 },
+	{ STM32F4_ADC_SQR2, GENMASK(29, 25), 25 },
+	{ STM32F4_ADC_SQR1, GENMASK(4, 0), 0 },
+	{ STM32F4_ADC_SQR1, GENMASK(9, 5), 5 },
+	{ STM32F4_ADC_SQR1, GENMASK(14, 10), 10 },
+	{ STM32F4_ADC_SQR1, GENMASK(19, 15), 15 },
+};
+
 /**
  * STM32 ADC registers access routines
  * @adc: stm32 adc instance
@@ -210,6 +261,104 @@ static void stm32_adc_stop_conv(struct stm32_adc *adc)
 	stm32_adc_clr_bits(adc, STM32F4_ADC_CR2, STM32F4_ADON);
 }
 
+/**
+ * stm32_adc_conf_scan_seq() - Build regular channels scan sequence
+ * @indio_dev: IIO device
+ * @scan_mask: channels to be converted
+ *
+ * Conversion sequence :
+ * Configure ADC scan sequence based on selected channels in scan_mask.
+ * Add channels to SQR registers, from scan_mask LSB to MSB, then
+ * program sequence len.
+ */
+static int stm32_adc_conf_scan_seq(struct iio_dev *indio_dev,
+				   const unsigned long *scan_mask)
+{
+	struct stm32_adc *adc = iio_priv(indio_dev);
+	const struct iio_chan_spec *chan;
+	u32 val, bit;
+	int i = 0;
+
+	for_each_set_bit(bit, scan_mask, indio_dev->masklength) {
+		chan = indio_dev->channels + bit;
+		/*
+		 * Assign one channel per SQ entry in regular
+		 * sequence, starting with SQ1.
+		 */
+		i++;
+		if (i > STM32_ADC_MAX_SQ)
+			return -EINVAL;
+
+		dev_dbg(&indio_dev->dev, "%s chan %d to SQ%d\n",
+			__func__, chan->channel, i);
+
+		val = stm32_adc_readl(adc, stm32f4_sq[i].reg);
+		val &= ~stm32f4_sq[i].mask;
+		val |= chan->channel << stm32f4_sq[i].shift;
+		stm32_adc_writel(adc, stm32f4_sq[i].reg, val);
+	}
+
+	if (!i)
+		return -EINVAL;
+
+	/* Sequence len */
+	val = stm32_adc_readl(adc, stm32f4_sq[0].reg);
+	val &= ~stm32f4_sq[0].mask;
+	val |= ((i - 1) << stm32f4_sq[0].shift);
+	stm32_adc_writel(adc, stm32f4_sq[0].reg, val);
+
+	return 0;
+}
+
+/**
+ * stm32_adc_get_trig_extsel() - Get external trigger selection
+ * @trig: trigger
+ *
+ * Returns trigger extsel value, if trig matches, -EINVAL otherwise.
+ */
+static int stm32_adc_get_trig_extsel(struct iio_trigger *trig)
+{
+	return -EINVAL;
+}
+
+/**
+ * stm32_adc_set_trig() - Set a regular trigger
+ * @indio_dev: IIO device
+ * @trig: IIO trigger
+ *
+ * Set trigger source/polarity (e.g. SW, or HW with polarity) :
+ * - if HW trigger disabled (e.g. trig == NULL, conversion launched by sw)
+ * - if HW trigger enabled, set source & polarity
+ */
+static int stm32_adc_set_trig(struct iio_dev *indio_dev,
+			      struct iio_trigger *trig)
+{
+	struct stm32_adc *adc = iio_priv(indio_dev);
+	u32 val, extsel = 0, exten = STM32_EXTEN_SWTRIG;
+	unsigned long flags;
+	int ret;
+
+	if (trig) {
+		ret = stm32_adc_get_trig_extsel(trig);
+		if (ret < 0)
+			return ret;
+
+		/* set trigger source and polarity (default to rising edge) */
+		extsel = ret;
+		exten = STM32_EXTEN_HWTRIG_RISING_EDGE;
+	}
+
+	spin_lock_irqsave(&adc->lock, flags);
+	val = stm32_adc_readl(adc, STM32F4_ADC_CR2);
+	val &= ~(STM32F4_EXTEN_MASK | STM32F4_EXTSEL_MASK);
+	val |= exten << STM32F4_EXTEN_SHIFT;
+	val |= extsel << STM32F4_EXTSEL_SHIFT;
+	stm32_adc_writel(adc, STM32F4_ADC_CR2, val);
+	spin_unlock_irqrestore(&adc->lock, flags);
+
+	return 0;
+}
+
 /**
  * stm32_adc_single_conv() - Performs a single conversion
  * @indio_dev: IIO device
@@ -228,21 +377,20 @@ static int stm32_adc_single_conv(struct iio_dev *indio_dev,
 	struct stm32_adc *adc = iio_priv(indio_dev);
 	long timeout;
 	u32 val;
-	u16 result;
 	int ret;
 
 	reinit_completion(&adc->completion);
 
-	adc->buffer = &result;
+	adc->bufi = 0;
 
-	/* Program chan number in regular sequence */
-	val = stm32_adc_readl(adc, STM32F4_ADC_SQR3);
-	val &= ~STM32F4_SQ1_MASK;
-	val |= chan->channel << STM32F4_SQ1_SHIFT;
-	stm32_adc_writel(adc, STM32F4_ADC_SQR3, val);
+	/* Program chan number in regular sequence (SQ1) */
+	val = stm32_adc_readl(adc, stm32f4_sq[1].reg);
+	val &= ~stm32f4_sq[1].mask;
+	val |= chan->channel << stm32f4_sq[1].shift;
+	stm32_adc_writel(adc, stm32f4_sq[1].reg, val);
 
 	/* Set regular sequence len (0 for 1 conversion) */
-	stm32_adc_clr_bits(adc, STM32F4_ADC_SQR1, STM32F4_L_MASK);
+	stm32_adc_clr_bits(adc, stm32f4_sq[0].reg, stm32f4_sq[0].mask);
 
 	/* Trigger detection disabled (conversion can be launched in SW) */
 	stm32_adc_clr_bits(adc, STM32F4_ADC_CR2, STM32F4_EXTEN_MASK);
@@ -258,7 +406,7 @@ static int stm32_adc_single_conv(struct iio_dev *indio_dev,
 	} else if (timeout < 0) {
 		ret = timeout;
 	} else {
-		*res = result;
+		*res = adc->buffer[0];
 		ret = IIO_VAL_INT;
 	}
 
@@ -301,17 +449,56 @@ static int stm32_adc_read_raw(struct iio_dev *indio_dev,
 static irqreturn_t stm32_adc_isr(int irq, void *data)
 {
 	struct stm32_adc *adc = data;
+	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
 	u32 status = stm32_adc_readl(adc, STM32F4_ADC_SR);
 
 	if (status & STM32F4_EOC) {
-		*adc->buffer = stm32_adc_readw(adc, STM32F4_ADC_DR);
-		complete(&adc->completion);
+		/* Reading DR also clears EOC status flag */
+		adc->buffer[adc->bufi] = stm32_adc_readw(adc, STM32F4_ADC_DR);
+		if (iio_buffer_enabled(indio_dev)) {
+			adc->bufi++;
+			if (adc->bufi >= adc->num_conv) {
+				stm32_adc_conv_irq_disable(adc);
+				iio_trigger_poll(indio_dev->trig);
+			}
+		} else {
+			complete(&adc->completion);
+		}
 		return IRQ_HANDLED;
 	}
 
 	return IRQ_NONE;
 }
 
+/**
+ * stm32_adc_validate_trigger() - validate trigger for stm32 adc
+ * @indio_dev: IIO device
+ * @trig: new trigger
+ *
+ * Returns: 0 if trig matches one of the triggers registered by stm32 adc
+ * driver, -EINVAL otherwise.
+ */
+static int stm32_adc_validate_trigger(struct iio_dev *indio_dev,
+				      struct iio_trigger *trig)
+{
+	return stm32_adc_get_trig_extsel(trig) < 0 ? -EINVAL : 0;
+}
+
+static int stm32_adc_update_scan_mode(struct iio_dev *indio_dev,
+				      const unsigned long *scan_mask)
+{
+	struct stm32_adc *adc = iio_priv(indio_dev);
+	int ret;
+
+	adc->num_conv = bitmap_weight(scan_mask, indio_dev->masklength);
+
+	ret = stm32_adc_conf_scan_seq(indio_dev, scan_mask);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
 static int stm32_adc_of_xlate(struct iio_dev *indio_dev,
 			      const struct of_phandle_args *iiospec)
 {
@@ -350,11 +537,86 @@ static int stm32_adc_debugfs_reg_access(struct iio_dev *indio_dev,
 
 static const struct iio_info stm32_adc_iio_info = {
 	.read_raw = stm32_adc_read_raw,
+	.validate_trigger = stm32_adc_validate_trigger,
+	.update_scan_mode = stm32_adc_update_scan_mode,
 	.debugfs_reg_access = stm32_adc_debugfs_reg_access,
 	.of_xlate = stm32_adc_of_xlate,
 	.driver_module = THIS_MODULE,
 };
 
+static int stm32_adc_buffer_postenable(struct iio_dev *indio_dev)
+{
+	struct stm32_adc *adc = iio_priv(indio_dev);
+	int ret;
+
+	ret = stm32_adc_set_trig(indio_dev, indio_dev->trig);
+	if (ret) {
+		dev_err(&indio_dev->dev, "Can't set trigger\n");
+		return ret;
+	}
+
+	ret = iio_triggered_buffer_postenable(indio_dev);
+	if (ret < 0)
+		goto err_clr_trig;
+
+	/* Reset adc buffer index */
+	adc->bufi = 0;
+
+	stm32_adc_conv_irq_enable(adc);
+	stm32_adc_start_conv(adc);
+
+	return 0;
+
+err_clr_trig:
+	stm32_adc_set_trig(indio_dev, NULL);
+
+	return ret;
+}
+
+static int stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
+{
+	struct stm32_adc *adc = iio_priv(indio_dev);
+	int ret;
+
+	stm32_adc_stop_conv(adc);
+	stm32_adc_conv_irq_disable(adc);
+
+	ret = iio_triggered_buffer_predisable(indio_dev);
+	if (ret < 0)
+		dev_err(&indio_dev->dev, "predisable failed\n");
+
+	if (stm32_adc_set_trig(indio_dev, NULL))
+		dev_err(&indio_dev->dev, "Can't clear trigger\n");
+
+	return ret;
+}
+
+static const struct iio_buffer_setup_ops stm32_adc_buffer_setup_ops = {
+	.postenable = &stm32_adc_buffer_postenable,
+	.predisable = &stm32_adc_buffer_predisable,
+};
+
+static irqreturn_t stm32_adc_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct stm32_adc *adc = iio_priv(indio_dev);
+
+	dev_dbg(&indio_dev->dev, "%s bufi=%d\n", __func__, adc->bufi);
+
+	/* reset buffer index */
+	adc->bufi = 0;
+	iio_push_to_buffers_with_timestamp(indio_dev, adc->buffer,
+					   pf->timestamp);
+
+	iio_trigger_notify_done(indio_dev->trig);
+
+	/* re-enable eoc irq */
+	stm32_adc_conv_irq_enable(adc);
+
+	return IRQ_HANDLED;
+}
+
 static void stm32_adc_chan_init_one(struct iio_dev *indio_dev,
 				    struct iio_chan_spec *chan,
 				    const struct stm32_adc_chan_spec *channel,
@@ -471,14 +733,26 @@ static int stm32_adc_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto err_clk_disable;
 
+	ret = iio_triggered_buffer_setup(indio_dev,
+					 &iio_pollfunc_store_time,
+					 &stm32_adc_trigger_handler,
+					 &stm32_adc_buffer_setup_ops);
+	if (ret) {
+		dev_err(&pdev->dev, "buffer setup failed\n");
+		goto err_clk_disable;
+	}
+
 	ret = iio_device_register(indio_dev);
 	if (ret) {
 		dev_err(&pdev->dev, "iio dev register failed\n");
-		goto err_clk_disable;
+		goto err_buffer_cleanup;
 	}
 
 	return 0;
 
+err_buffer_cleanup:
+	iio_triggered_buffer_cleanup(indio_dev);
+
 err_clk_disable:
 	clk_disable_unprepare(adc->clk);
 
@@ -491,6 +765,7 @@ static int stm32_adc_remove(struct platform_device *pdev)
 	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
 
 	iio_device_unregister(indio_dev);
+	iio_triggered_buffer_cleanup(indio_dev);
 	clk_disable_unprepare(adc->clk);
 
 	return 0;