[PATCH 08/10] iio: adc: at91-sama5d2_adc: implement RTC triggering

[<Eugen.Hristev@microchip.com>]

From: Eugen Hristev <eugen.hristev@microchip.com>

Implement the property atmel,rtc-trigger which provides a phandle
to a RTC trigger.
To make it work, one has to check at buffer_postenable if the trigger
the device is using is the one we provide using the phandle link.
The trigger mode must be selected accordingly in the trigger mode selection
register.
The RTC trigger will use our IRQ. Dedicated hardware line inside the SoC
will actually trigger the ADC to make the conversion, and EOC irqs are fired
when conversion is done.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
---
 drivers/iio/adc/at91-sama5d2_adc.c | 109 +++++++++++++++++++++++++++++++++++--
 1 file changed, 104 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index ccffa48..ac97f4a 100644
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -58,6 +58,8 @@
 #define	AT91_SAMA5D2_MR_TRGSEL_TRIG6	6
 /* RTCOUT0 */
 #define	AT91_SAMA5D2_MR_TRGSEL_TRIG7	7
+/* TRGSEL mask */
+#define AT91_SAMA5D2_MR_TRGSEL_MASK	GENMASK(3, 1)
 /* Sleep Mode */
 #define	AT91_SAMA5D2_MR_SLEEP		BIT(5)
 /* Fast Wake Up */
@@ -195,6 +197,8 @@
 #define AT91_SAMA5D2_TRGR_TRGMOD_EXT_TRIG_FALL 2
 /* Trigger Mode external trigger any edge */
 #define AT91_SAMA5D2_TRGR_TRGMOD_EXT_TRIG_ANY 3
+/* Trigger Mode RTC - must be any of the above 3 values */
+#define AT91_SAMA5D2_TRGR_TRGMOD_RTC AT91_SAMA5D2_TRGR_TRGMOD_EXT_TRIG_RISE
 /* Trigger Mode internal periodic */
 #define AT91_SAMA5D2_TRGR_TRGMOD_PERIODIC 5
 /* Trigger Mode - trigger period mask */
@@ -407,6 +411,8 @@ struct at91_adc_state {
 	struct mutex			lock;
 	struct work_struct		workq;
 	s64				timestamp;
+	struct device			*rtc_trig_dev;
+	bool				rtc_triggered;
 };
 
 static const struct at91_adc_trigger at91_adc_trigger_list[] = {
@@ -737,6 +743,42 @@ static int at91_adc_configure_trigger(struct iio_trigger *trig, bool state)
 	/* set/unset hw trigger */
 	at91_adc_writel(st, AT91_SAMA5D2_TRGR, status);
 
+	status = at91_adc_readl(st, AT91_SAMA5D2_MR);
+
+	status &= ~AT91_SAMA5D2_MR_TRGSEL_MASK;
+
+	/* set/unset TRGSEL to ADTRG */
+	if (state)
+		status |= AT91_SAMA5D2_MR_TRGSEL(AT91_SAMA5D2_MR_TRGSEL_TRIG0);
+
+	at91_adc_writel(st, AT91_SAMA5D2_MR, status);
+
+	return 0;
+}
+
+static int at91_adc_rtc_configure_trigger(struct at91_adc_state *st, bool state)
+{
+	u32 status = at91_adc_readl(st, AT91_SAMA5D2_TRGR);
+
+	/* clear TRGMOD */
+	status &= ~AT91_SAMA5D2_TRGR_TRGMOD_MASK;
+
+	if (state)
+		status |= AT91_SAMA5D2_TRGR_TRGMOD_RTC;
+
+	/* set/unset hw trigger */
+	at91_adc_writel(st, AT91_SAMA5D2_TRGR, status);
+
+	status = at91_adc_readl(st, AT91_SAMA5D2_MR);
+
+	status &= ~AT91_SAMA5D2_MR_TRGSEL_MASK;
+
+	/* set/unset TRGSEL to RTCOUT0 */
+	if (state)
+		status |= AT91_SAMA5D2_MR_TRGSEL(AT91_SAMA5D2_MR_TRGSEL_TRIG7);
+
+	at91_adc_writel(st, AT91_SAMA5D2_MR, status);
+
 	return 0;
 }
 
@@ -866,7 +908,8 @@ static int at91_adc_dma_start(struct iio_dev *indio_dev)
 	if (st->dma_st.dma_chan) \
 		use_irq = false; \
 	/* if the trigger is not ours, then it has its own IRQ */ \
-	if (iio_trigger_validate_own_device(indio->trig, indio)) \
+	if (iio_trigger_validate_own_device(indio->trig, indio) && \
+		!st->rtc_triggered) \
 		use_irq = false; \
 	}
 
@@ -884,6 +927,18 @@ static int at91_adc_buffer_postenable(struct iio_dev *indio)
 		/* touchscreen enabling */
 		return at91_adc_configure_touch(st, true);
 	}
+
+	/*
+	 * If our rtc trigger link is identical to the current trigger,
+	 * then we are rtc-triggered.
+	 * Configure accordingly.
+	 */
+	if (!IS_ERR_OR_NULL(st->rtc_trig_dev) &&
+	    st->rtc_trig_dev == indio->trig->dev.parent) {
+		at91_adc_rtc_configure_trigger(st, true);
+		st->rtc_triggered = true;
+	}
+
 	/* if we are not in triggered mode, we cannot enable the buffer. */
 	if (!(indio->currentmode & INDIO_ALL_TRIGGERED_MODES))
 		return -EINVAL;
@@ -947,6 +1002,17 @@ static int at91_adc_buffer_predisable(struct iio_dev *indio)
 	if (!(indio->currentmode & INDIO_ALL_TRIGGERED_MODES))
 		return -EINVAL;
 
+	/*
+	 * If our rtc trigger link is identical to the current trigger,
+	 * then we are rtc-triggered.
+	 * Unconfigure accordingly.
+	 */
+	if (!IS_ERR_OR_NULL(st->rtc_trig_dev) &&
+	    st->rtc_trig_dev == indio->trig->dev.parent) {
+		at91_adc_rtc_configure_trigger(st, false);
+		st->rtc_triggered = false;
+	}
+
 	AT91_ADC_BUFFER_CHECK_USE_IRQ(use_irq);
 	/*
 	 * For each enable channel we must disable it in hardware.
@@ -1153,8 +1219,15 @@ static irqreturn_t at91_adc_trigger_handler(int irq, void *p)
 	else
 		ret = at91_adc_trigger_handler_nodma(indio_dev, pf);
 
-	if (!ret)
+	if (!ret) {
 		iio_trigger_notify_done(indio_dev->trig);
+		/*
+		 * RTC trigger does not know how to reenable our IRQ.
+		 * So, we must do it.
+		 */
+		if (st->rtc_triggered)
+			enable_irq(st->irq);
+	}
 
 	return IRQ_HANDLED;
 }
@@ -1166,10 +1239,13 @@ irqreturn_t at91_adc_pollfunc(int irq, void *p)
 	struct at91_adc_state *st = iio_priv(indio_dev);
 
 	/*
-	 * If it's not our trigger, start a conversion now, as we are
-	 * actually polling the trigger now.
+	 * We need to start a software trigger if we are not using a trigger
+	 * that uses our own IRQ.
+	 * External trigger and RTC trigger do not not need software start
+	 * However the other triggers do.
 	 */
-	if (iio_trigger_validate_own_device(indio_dev->trig, indio_dev))
+	if (iio_trigger_validate_own_device(indio_dev->trig, indio_dev) &&
+	    !st->rtc_triggered)
 		at91_adc_writel(st, AT91_SAMA5D2_CR, AT91_SAMA5D2_CR_START);
 
 	return iio_pollfunc_store_time(irq, p);
@@ -1307,6 +1383,12 @@ static void at91_adc_workq_handler(struct work_struct *workq)
 
 		at91_adc_read_and_push_channels(indio_dev, st->timestamp);
 		iio_trigger_notify_done(indio_dev->trig);
+		/*
+		 * RTC trigger does not know how to reenable our IRQ.
+		 * So, we must do it.
+		 */
+		if (st->rtc_triggered)
+			enable_irq(st->irq);
 	} else {
 		iio_push_to_buffers(indio_dev, st->buffer);
 	}
@@ -1712,6 +1794,7 @@ static int at91_adc_probe(struct platform_device *pdev)
 	struct iio_dev *indio_dev;
 	struct at91_adc_state *st;
 	struct resource	*res;
+	struct device_node *rtc_trig_np;
 	int ret, i;
 	u32 edge_type = IRQ_TYPE_NONE;
 
@@ -1737,6 +1820,8 @@ static int at91_adc_probe(struct platform_device *pdev)
 
 	st->oversampling_ratio = AT91_OSR_1SAMPLES;
 
+	st->rtc_trig_dev = ERR_PTR(-EINVAL);
+
 	ret = of_property_read_u32(pdev->dev.of_node,
 				   "atmel,min-sample-rate-hz",
 				   &st->soc_info.min_sample_rate);
@@ -1784,6 +1869,20 @@ static int at91_adc_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
+	rtc_trig_np = of_parse_phandle(pdev->dev.of_node, "atmel,rtc-trigger",
+				       0);
+	if (rtc_trig_np) {
+		struct platform_device *rtc_trig_plat_dev;
+
+		rtc_trig_plat_dev = of_find_device_by_node(rtc_trig_np);
+		if (rtc_trig_plat_dev) {
+			st->rtc_trig_dev = &rtc_trig_plat_dev->dev;
+			dev_info(&pdev->dev,
+				 "RTC trigger link set-up with %s\n",
+				 dev_name(st->rtc_trig_dev));
+		}
+	}
+
 	init_waitqueue_head(&st->wq_data_available);
 	mutex_init(&st->lock);
 	INIT_WORK(&st->workq, at91_adc_workq_handler);
-- 
2.7.4