Date:   Thu, 21 Mar 2019 17:47:28 +0100
From:   Fabrice Gasnier <fabrice.gasnier@...com>
To:     <jic23@...nel.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <mcoquelin.stm32@...il.com>,
        <alexandre.torgue@...com>, <fabrice.gasnier@...com>,
        <linux-iio@...r.kernel.org>, <lars@...afoo.de>, <knaack.h@....de>,
        <pmeerw@...erw.net>, <linux-stm32@...md-mailman.stormreply.com>,
        <arnaud.pouliquen@...com>, <olivier.moysan@...com>
Subject: [PATCH v2 7/8] iio: adc: stm32-dfsdm: add support for buffer modes

DFSDM conversions can be launched continuously, or using various
triggers:
- by software
- hardware triggers (e.g. like in stm32-adc: TIM, LPTIM, EXTI)
- synchronously with DFSDM filter 0. e.g. for filters 1, 2

Launching conversions can be done using two methods:
a - injected:
    - scan mode can be used to convert several channels each time a
      trigger occurs.
    - When not is scan mode, channels are converted in sequence, one upon
      each trigger.
b - regular:
    - supports software triggers or synchronous with filter 0
    - single or continuous conversions

This patch finalizes DFSDM operating modes using IIO buffer modes:
- INDIO_BUFFER_SOFTWARE: regular continuous conversions (no trigger)
  but limited to 1 channel. Users must set sampling frequency in this case.
  For filters > 1, conversions can be started synchronously with filter 0.
- INDIO_BUFFER_TRIGGERED: triggered conversions uses injected mode for
  launching conversions. DFSDM can use hardware triggers (e.g. STM32 timer
  or lptimer), so add INDIO_HARDWARE_TRIGGERED to supported modes.
- INDIO_DIRECT_MODE: Only support DMA-based buffer modes. In case no DMA is
  available, only support single conversions.

>From userland perspective, to summarize various use cases:
1 - single conversion on any filter:
$ cd iio:deviceX
$ cat in_voltageY_raw
This uses regular a conversion (not continuous)

2 - Using sampling frequency without trigger (single channel, buffer)
$ cd iio:deviceX
$ echo 100 > sampling_frequency
$ echo "" > trigger/current_trigger
$ echo 1 > scan_elements/in_voltageY_en
$ echo 1 > buffer/enable
This uses regular conversion in continuous mode (Frequency is achieved
by tuning filter parameters)

3 - sync mode with filter 0: other filters can be converted when using
"st,filter0-sync" dt property. The conversions will get started at the
same time as filter 0. So for any filters > 1:
$ cd iio:deviceX
$ echo 100 > sampling_frequency
$ echo "" > trigger/current_trigger
$ echo 1 > scan_elements/in_voltageY_en
$ echo 1 > buffer/enable
Then start filter 0 as in 2 above.

4 - Using a hardware trigger (with one channel):
- check trigger, configure it:
$ cat /sys/bus/iio/devices/trigger1/name
tim6_trgo
$ echo 100 > /sys/bus/iio/devices/trigger1/sampling_frequency
- go to any filter:
$ echo 1 > scan_elements/in_voltageY_en
$ echo tim6_trgo > trigger/current_trigger
$ echo 1 > buffer/enable
This uses injected conversion as it uses a hardware trigger (without scan)

5 - Using a hardware trigger (with 2+ channel):
Same as in 4/ above, but enable two or more channels in scan_elements.
This uses injected conversion as it uses a hardware trigger (with scan mode)

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
---
Changes in v2:
- Update the patch description to better explain working modes and the way
  to use them from user perspective
---
 drivers/iio/adc/stm32-dfsdm-adc.c | 218 +++++++++++++++++++++++++++++++++-----
 1 file changed, 194 insertions(+), 24 deletions(-)

diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
index 4ead6bf..51688eb 100644
--- a/drivers/iio/adc/stm32-dfsdm-adc.c
+++ b/drivers/iio/adc/stm32-dfsdm-adc.c
@@ -12,6 +12,11 @@
 #include <linux/iio/buffer.h>
 #include <linux/iio/hw-consumer.h>
 #include <linux/iio/sysfs.h>
+#include <linux/iio/timer/stm32-lptim-trigger.h>
+#include <linux/iio/timer/stm32-timer-trigger.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
@@ -121,6 +126,61 @@ static int stm32_dfsdm_str2val(const char *str,
 	return -EINVAL;
 }
 
+/**
+ * struct stm32_dfsdm_trig_info - DFSDM trigger info
+ * @name:		name of the trigger, corresponding to its source
+ * @jextsel:		trigger signal selection
+ */
+struct stm32_dfsdm_trig_info {
+	const char *name;
+	unsigned int jextsel;
+};
+
+/* hardware injected trigger enable, edge selection */
+enum stm32_dfsdm_jexten {
+	STM32_DFSDM_JEXTEN_DISABLED,
+	STM32_DFSDM_JEXTEN_RISING_EDGE,
+	STM32_DFSDM_JEXTEN_FALLING_EDGE,
+	STM32_DFSDM_EXTEN_BOTH_EDGES,
+};
+
+static const struct stm32_dfsdm_trig_info stm32_dfsdm_trigs[] = {
+	{ TIM1_TRGO, 0 },
+	{ TIM1_TRGO2, 1 },
+	{ TIM8_TRGO, 2 },
+	{ TIM8_TRGO2, 3 },
+	{ TIM3_TRGO, 4 },
+	{ TIM4_TRGO, 5 },
+	{ TIM16_OC1, 6 },
+	{ TIM6_TRGO, 7 },
+	{ TIM7_TRGO, 8 },
+	{ LPTIM1_OUT, 26 },
+	{ LPTIM2_OUT, 27 },
+	{ LPTIM3_OUT, 28 },
+	{},
+};
+
+static int stm32_dfsdm_get_jextsel(struct iio_dev *indio_dev,
+				   struct iio_trigger *trig)
+{
+	int i;
+
+	/* lookup triggers registered by stm32 timer trigger driver */
+	for (i = 0; stm32_dfsdm_trigs[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) ||
+		     is_stm32_lptim_trigger(trig)) &&
+		    !strcmp(stm32_dfsdm_trigs[i].name, trig->name)) {
+			return stm32_dfsdm_trigs[i].jextsel;
+		}
+	}
+
+	return -EINVAL;
+}
+
 static int stm32_dfsdm_set_osrs(struct stm32_dfsdm_filter *fl,
 				unsigned int fast, unsigned int oversamp)
 {
@@ -265,7 +325,8 @@ static int stm32_dfsdm_chan_configure(struct stm32_dfsdm *dfsdm,
 }
 
 static int stm32_dfsdm_start_filter(struct stm32_dfsdm_adc *adc,
-				    unsigned int fl_id)
+				    unsigned int fl_id,
+				    struct iio_trigger *trig)
 {
 	struct stm32_dfsdm *dfsdm = adc->dfsdm;
 	int ret;
@@ -277,7 +338,7 @@ static int stm32_dfsdm_start_filter(struct stm32_dfsdm_adc *adc,
 		return ret;
 
 	/* Nothing more to do for injected (scan mode/triggered) conversions */
-	if (adc->nconv > 1)
+	if (adc->nconv > 1 || trig)
 		return 0;
 
 	/* Software start (single or continuous) regular conversion */
@@ -294,8 +355,38 @@ static void stm32_dfsdm_stop_filter(struct stm32_dfsdm *dfsdm,
 			   DFSDM_CR1_DFEN_MASK, DFSDM_CR1_DFEN(0));
 }
 
+static int stm32_dfsdm_filter_set_trig(struct stm32_dfsdm_adc *adc,
+				       unsigned int fl_id,
+				       struct iio_trigger *trig)
+{
+	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
+	struct regmap *regmap = adc->dfsdm->regmap;
+	u32 jextsel = 0, jexten = STM32_DFSDM_JEXTEN_DISABLED;
+	int ret;
+
+	if (trig) {
+		ret = stm32_dfsdm_get_jextsel(indio_dev, trig);
+		if (ret < 0)
+			return ret;
+
+		/* set trigger source and polarity (default to rising edge) */
+		jextsel = ret;
+		jexten = STM32_DFSDM_JEXTEN_RISING_EDGE;
+	}
+
+	ret = regmap_update_bits(regmap, DFSDM_CR1(fl_id),
+				 DFSDM_CR1_JEXTSEL_MASK | DFSDM_CR1_JEXTEN_MASK,
+				 DFSDM_CR1_JEXTSEL(jextsel) |
+				 DFSDM_CR1_JEXTEN(jexten));
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
 static int stm32_dfsdm_filter_configure(struct stm32_dfsdm_adc *adc,
-					unsigned int fl_id)
+					unsigned int fl_id,
+					struct iio_trigger *trig)
 {
 	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
 	struct regmap *regmap = adc->dfsdm->regmap;
@@ -322,6 +413,10 @@ static int stm32_dfsdm_filter_configure(struct stm32_dfsdm_adc *adc,
 	if (ret)
 		return ret;
 
+	ret = stm32_dfsdm_filter_set_trig(adc, fl_id, trig);
+	if (ret)
+		return ret;
+
 	/*
 	 * DFSDM modes configuration W.R.T audio/iio type modes
 	 * ----------------------------------------------------------------
@@ -341,7 +436,7 @@ static int stm32_dfsdm_filter_configure(struct stm32_dfsdm_adc *adc,
 	 *               |         |              |          | sync_mode  |
 	 * ----------------------------------------------------------------
 	 */
-	if (adc->nconv == 1) {
+	if (adc->nconv == 1 && !trig) {
 		bit = __ffs(adc->smask);
 		chan = indio_dev->channels + bit;
 
@@ -365,13 +460,15 @@ static int stm32_dfsdm_filter_configure(struct stm32_dfsdm_adc *adc,
 			return ret;
 
 		/* Use scan mode for multiple channels */
-		cr1 = DFSDM_CR1_JSCAN(1);
+		cr1 = DFSDM_CR1_JSCAN(!!(adc->nconv > 1));
 
 		/*
-		 * Continuous conversions not supported in injected mode:
-		 * - use conversions in sync with filter 0
+		 * Continuous conversions not supported in injected mode,
+		 * either use:
+		 * - conversions in sync with filter 0
+		 * - triggered conversions
 		 */
-		if (!fl->sync_mode)
+		if (!fl->sync_mode && !trig)
 			return -EINVAL;
 		cr1 |= DFSDM_CR1_JSYNC(fl->sync_mode);
 	}
@@ -503,7 +600,8 @@ static ssize_t dfsdm_adc_audio_set_spiclk(struct iio_dev *indio_dev,
 	return len;
 }
 
-static int stm32_dfsdm_start_conv(struct stm32_dfsdm_adc *adc)
+static int stm32_dfsdm_start_conv(struct stm32_dfsdm_adc *adc,
+				  struct iio_trigger *trig)
 {
 	struct regmap *regmap = adc->dfsdm->regmap;
 	int ret;
@@ -512,11 +610,11 @@ static int stm32_dfsdm_start_conv(struct stm32_dfsdm_adc *adc)
 	if (ret < 0)
 		return ret;
 
-	ret = stm32_dfsdm_filter_configure(adc, adc->fl_id);
+	ret = stm32_dfsdm_filter_configure(adc, adc->fl_id, trig);
 	if (ret < 0)
 		goto stop_channels;
 
-	ret = stm32_dfsdm_start_filter(adc, adc->fl_id);
+	ret = stm32_dfsdm_start_filter(adc, adc->fl_id, trig);
 	if (ret < 0)
 		goto filter_unconfigure;
 
@@ -548,6 +646,7 @@ static int stm32_dfsdm_set_watermark(struct iio_dev *indio_dev,
 {
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
 	unsigned int watermark = DFSDM_DMA_BUFFER_SIZE / 2;
+	unsigned int rx_buf_sz = DFSDM_DMA_BUFFER_SIZE;
 
 	/*
 	 * DMA cyclic transfers are used, buffer is split into two periods.
@@ -556,7 +655,7 @@ static int stm32_dfsdm_set_watermark(struct iio_dev *indio_dev,
 	 * - one buffer (period) driver pushed to ASoC side.
 	 */
 	watermark = min(watermark, val * (unsigned int)(sizeof(u32)));
-	adc->buf_sz = watermark * 2;
+	adc->buf_sz = min(rx_buf_sz, watermark * 2 * adc->nconv);
 
 	return 0;
 }
@@ -586,13 +685,41 @@ static unsigned int stm32_dfsdm_adc_dma_residue(struct stm32_dfsdm_adc *adc)
 	return 0;
 }
 
-static void stm32_dfsdm_audio_dma_buffer_done(void *data)
+static irqreturn_t stm32_dfsdm_adc_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
+	int available = stm32_dfsdm_adc_dma_residue(adc);
+
+	while (available >= indio_dev->scan_bytes) {
+		u32 *buffer = (u32 *)&adc->rx_buf[adc->bufi];
+
+		iio_push_to_buffers_with_timestamp(indio_dev, buffer,
+						   pf->timestamp);
+		available -= indio_dev->scan_bytes;
+		adc->bufi += indio_dev->scan_bytes;
+		if (adc->bufi >= adc->buf_sz)
+			adc->bufi = 0;
+	}
+
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static void stm32_dfsdm_dma_buffer_done(void *data)
 {
 	struct iio_dev *indio_dev = data;
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
 	int available = stm32_dfsdm_adc_dma_residue(adc);
 	size_t old_pos;
 
+	if (indio_dev->currentmode & INDIO_BUFFER_TRIGGERED) {
+		iio_trigger_poll_chained(indio_dev->trig);
+		return;
+	}
+
 	/*
 	 * FIXME: In Kernel interface does not support cyclic DMA buffer,and
 	 * offers only an interface to push data samples per samples.
@@ -620,6 +747,9 @@ static void stm32_dfsdm_audio_dma_buffer_done(void *data)
 			adc->bufi = 0;
 			old_pos = 0;
 		}
+		/* regular iio buffer without trigger */
+		if (adc->dev_data->type == DFSDM_IIO)
+			iio_push_to_buffers(indio_dev, buffer);
 	}
 	if (adc->cb)
 		adc->cb(&adc->rx_buf[old_pos], adc->bufi - old_pos,
@@ -643,7 +773,7 @@ static int stm32_dfsdm_adc_dma_start(struct iio_dev *indio_dev)
 	dev_dbg(&indio_dev->dev, "%s size=%d watermark=%d\n", __func__,
 		adc->buf_sz, adc->buf_sz / 2);
 
-	if (adc->nconv == 1)
+	if (adc->nconv == 1 && !indio_dev->trig)
 		config.src_addr += DFSDM_RDATAR(adc->fl_id);
 	else
 		config.src_addr += DFSDM_JDATAR(adc->fl_id);
@@ -660,7 +790,7 @@ static int stm32_dfsdm_adc_dma_start(struct iio_dev *indio_dev)
 	if (!desc)
 		return -EBUSY;
 
-	desc->callback = stm32_dfsdm_audio_dma_buffer_done;
+	desc->callback = stm32_dfsdm_dma_buffer_done;
 	desc->callback_param = indio_dev;
 
 	cookie = dmaengine_submit(desc);
@@ -671,7 +801,7 @@ static int stm32_dfsdm_adc_dma_start(struct iio_dev *indio_dev)
 	/* Issue pending DMA requests */
 	dma_async_issue_pending(adc->dma_chan);
 
-	if (adc->nconv == 1) {
+	if (adc->nconv == 1 && !indio_dev->trig) {
 		/* Enable regular DMA transfer*/
 		ret = regmap_update_bits(adc->dfsdm->regmap,
 					 DFSDM_CR1(adc->fl_id),
@@ -726,13 +856,19 @@ static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
 	int ret;
 
+	if (indio_dev->currentmode == INDIO_BUFFER_TRIGGERED) {
+		ret = iio_triggered_buffer_postenable(indio_dev);
+		if (ret < 0)
+			return ret;
+	}
+
 	/* Reset adc buffer index */
 	adc->bufi = 0;
 
 	if (adc->hwc) {
 		ret = iio_hw_consumer_enable(adc->hwc);
 		if (ret < 0)
-			return ret;
+			goto err_predisable;
 	}
 
 	ret = stm32_dfsdm_start_dfsdm(adc->dfsdm);
@@ -745,7 +881,7 @@ static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
 		goto stop_dfsdm;
 	}
 
-	ret = stm32_dfsdm_start_conv(adc);
+	ret = stm32_dfsdm_start_conv(adc, indio_dev->trig);
 	if (ret) {
 		dev_err(&indio_dev->dev, "Can't start conversion\n");
 		goto err_stop_dma;
@@ -760,6 +896,9 @@ static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
 err_stop_hwc:
 	if (adc->hwc)
 		iio_hw_consumer_disable(adc->hwc);
+err_predisable:
+	if (indio_dev->currentmode == INDIO_BUFFER_TRIGGERED)
+		iio_triggered_buffer_predisable(indio_dev);
 
 	return ret;
 }
@@ -777,6 +916,9 @@ static int stm32_dfsdm_predisable(struct iio_dev *indio_dev)
 	if (adc->hwc)
 		iio_hw_consumer_disable(adc->hwc);
 
+	if (indio_dev->currentmode == INDIO_BUFFER_TRIGGERED)
+		iio_triggered_buffer_predisable(indio_dev);
+
 	return 0;
 }
 
@@ -856,7 +998,7 @@ static int stm32_dfsdm_single_conv(struct iio_dev *indio_dev,
 
 	adc->nconv = 1;
 	adc->smask = BIT(chan->scan_index);
-	ret = stm32_dfsdm_start_conv(adc);
+	ret = stm32_dfsdm_start_conv(adc, NULL);
 	if (ret < 0) {
 		regmap_update_bits(adc->dfsdm->regmap, DFSDM_CR2(adc->fl_id),
 				   DFSDM_CR2_REOCIE_MASK, DFSDM_CR2_REOCIE(0));
@@ -978,6 +1120,12 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
 	return -EINVAL;
 }
 
+static int stm32_dfsdm_validate_trigger(struct iio_dev *indio_dev,
+					struct iio_trigger *trig)
+{
+	return stm32_dfsdm_get_jextsel(indio_dev, trig) < 0 ? -EINVAL : 0;
+}
+
 static const struct iio_info stm32_dfsdm_info_audio = {
 	.hwfifo_set_watermark = stm32_dfsdm_set_watermark,
 	.read_raw = stm32_dfsdm_read_raw,
@@ -986,9 +1134,11 @@ static const struct iio_info stm32_dfsdm_info_audio = {
 };
 
 static const struct iio_info stm32_dfsdm_info_adc = {
+	.hwfifo_set_watermark = stm32_dfsdm_set_watermark,
 	.read_raw = stm32_dfsdm_read_raw,
 	.write_raw = stm32_dfsdm_write_raw,
 	.update_scan_mode = stm32_dfsdm_update_scan_mode,
+	.validate_trigger = stm32_dfsdm_validate_trigger,
 };
 
 static irqreturn_t stm32_dfsdm_irq(int irq, void *arg)
@@ -1061,6 +1211,9 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
 		return -ENOMEM;
 	}
 
+	indio_dev->modes |= INDIO_BUFFER_SOFTWARE;
+	indio_dev->setup_ops = &stm32_dfsdm_buffer_setup_ops;
+
 	return 0;
 }
 
@@ -1082,7 +1235,8 @@ static int stm32_dfsdm_adc_chan_init_one(struct iio_dev *indio_dev,
 	 * IIO_CHAN_INFO_OVERSAMPLING_RATIO: used to set oversampling
 	 */
 	ch->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
-	ch->info_mask_shared_by_all = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO);
+	ch->info_mask_shared_by_all = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
+					BIT(IIO_CHAN_INFO_SAMP_FREQ);
 
 	if (adc->dev_data->type == DFSDM_AUDIO) {
 		ch->scan_type.sign = 's';
@@ -1104,9 +1258,6 @@ static int stm32_dfsdm_audio_init(struct iio_dev *indio_dev)
 	struct stm32_dfsdm_channel *d_ch;
 	int ret;
 
-	indio_dev->modes |= INDIO_BUFFER_SOFTWARE;
-	indio_dev->setup_ops = &stm32_dfsdm_buffer_setup_ops;
-
 	ch = devm_kzalloc(&indio_dev->dev, sizeof(*ch), GFP_KERNEL);
 	if (!ch)
 		return -ENOMEM;
@@ -1174,6 +1325,25 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
 
 	init_completion(&adc->completion);
 
+	/* Optionally request DMA */
+	if (stm32_dfsdm_dma_request(indio_dev)) {
+		dev_dbg(&indio_dev->dev, "No DMA support\n");
+		return 0;
+	}
+
+	ret = iio_triggered_buffer_setup(indio_dev,
+					 &iio_pollfunc_store_time,
+					 &stm32_dfsdm_adc_trigger_handler,
+					 &stm32_dfsdm_buffer_setup_ops);
+	if (ret) {
+		stm32_dfsdm_dma_release(indio_dev);
+		dev_err(&indio_dev->dev, "buffer setup failed\n");
+		return ret;
+	}
+
+	/* lptimer/timer hardware triggers */
+	indio_dev->modes |= INDIO_HARDWARE_TRIGGERED;
+
 	return 0;
 }
 
@@ -1221,7 +1391,7 @@ static int stm32_dfsdm_adc_probe(struct platform_device *pdev)
 
 	iio->dev.parent = dev;
 	iio->dev.of_node = np;
-	iio->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
+	iio->modes = INDIO_DIRECT_MODE;
 
 	platform_set_drvdata(pdev, adc);
 
-- 
2.7.4

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