[PATCH v3 6/6] iio: adc: stm32: add support for EXTI trigger

[Fabrice Gasnier]

EXTi (external interrupt) signal can be routed internally as trigger
source for ADC conversions: STM32F4 ADC can use EXTI11.

Retrieve interrupt trigger from DT, so it can be muxed into ADC IP,
via extsel.

Signed-off-by: Fabrice Gasnier <fabrice.gasn...@st.com>
---
 drivers/iio/adc/stm32-adc.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 9b49a6ad..4d9040d 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -108,6 +108,9 @@ enum stm32_adc_extsel {
        STM32_EXT15,
 };
 
+/* EXTI 11 trigger selection on STM32F4 */
+#define STM32F4_EXTI11_EXTSEL          STM32_EXT15
+
 /**
  * struct stm32_adc_trig_info - ADC trigger info
  * @name:              name of the trigger, corresponding to its source
@@ -146,6 +149,7 @@ struct stm32_adc_regs {
  * @rx_buf:            dma rx buffer cpu address
  * @rx_dma_buf:                dma rx buffer bus address
  * @rx_buf_sz:         dma rx buffer size
+ * @exti_trig          EXTI trigger
  */
 struct stm32_adc {
        struct stm32_adc_common *common;
@@ -162,6 +166,7 @@ struct stm32_adc {
        u8                      *rx_buf;
        dma_addr_t              rx_dma_buf;
        unsigned int            rx_buf_sz;
+       struct iio_trigger      *exti_trig;
 };
 
 /**
@@ -395,10 +400,15 @@ static int stm32_adc_conf_scan_seq(struct iio_dev 
*indio_dev,
  *
  * Returns trigger extsel value, if trig matches, -EINVAL otherwise.
  */
-static int stm32_adc_get_trig_extsel(struct iio_trigger *trig)
+static int stm32_adc_get_trig_extsel(struct iio_dev *indio_dev,
+                                    struct iio_trigger *trig)
 {
+       struct stm32_adc *adc = iio_priv(indio_dev);
        int i;
 
+       if (trig == adc->exti_trig)
+               return STM32F4_EXTI11_EXTSEL;
+
        /* lookup triggers registered by stm32 timer trigger driver */
        for (i = 0; stm32f4_adc_trigs[i].name; i++) {
                /**
@@ -432,7 +442,7 @@ static int stm32_adc_set_trig(struct iio_dev *indio_dev,
        int ret;
 
        if (trig) {
-               ret = stm32_adc_get_trig_extsel(trig);
+               ret = stm32_adc_get_trig_extsel(indio_dev, trig);
                if (ret < 0)
                        return ret;
 
@@ -604,7 +614,7 @@ static irqreturn_t stm32_adc_isr(int irq, void *data)
 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;
+       return stm32_adc_get_trig_extsel(indio_dev, trig) < 0 ? -EINVAL : 0;
 }
 
 static int stm32_adc_set_watermark(struct iio_dev *indio_dev, unsigned int val)
@@ -1030,6 +1040,17 @@ static int stm32_adc_probe(struct platform_device *pdev)
        if (ret < 0)
                goto err_clk_disable;
 
+       adc->exti_trig = devm_iio_trigger_get_by_name(&pdev->dev, "exti");
+       if (IS_ERR(adc->exti_trig)) {
+               ret = PTR_ERR(adc->exti_trig);
+               if (ret == -EPROBE_DEFER)
+                       goto err_dma_disable;
+               dev_dbg(&pdev->dev, "No exti trigger found (%d)\n", ret);
+               adc->exti_trig = NULL;
+       } else {
+               dev_info(&pdev->dev, "Can use %s\n", adc->exti_trig->name);
+       }
+
        ret = iio_triggered_buffer_setup(indio_dev,
                                         &iio_pollfunc_store_time,
                                         &stm32_adc_trigger_handler,
-- 
1.9.1