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Date:   Sat, 16 Mar 2019 14:10:12 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Fabrice Gasnier <fabrice.gasnier@st.com>
Cc:     <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <mcoquelin.stm32@gmail.com>,
        <alexandre.torgue@st.com>, <linux-iio@vger.kernel.org>,
        <lars@metafoo.de>, <knaack.h@gmx.de>, <pmeerw@pmeerw.net>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        <arnaud.pouliquen@st.com>, <olivier.moysan@st.com>
Subject: Re: [PATCH 7/8] iio: adc: stm32-dfsdm: add support for buffer modes
Message-ID: <20190316141012.01ae0f77@archlinux>
In-Reply-To: <d2463873-fd8c-7c74-80d5-b7685772d84c@st.com>
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        <1551862524-25098-8-git-send-email-fabrice.gasnier@st.com>
        <20190310102114.0c1e7bd8@archlinux>
        <d2463873-fd8c-7c74-80d5-b7685772d84c@st.com>
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On Fri, 15 Mar 2019 19:01:47 +0100
Fabrice Gasnier <fabrice.gasnier@st.com> wrote:

> On 3/10/19 11:21 AM, Jonathan Cameron wrote:
> > On Wed, 6 Mar 2019 09:55:23 +0100
> > Fabrice Gasnier <fabrice.gasnier@st.com> wrote:
> >   
> >> DFSDM can operate using these buffer modes:
> >> - INDIO_BUFFER_SOFTWARE: regular continuous conversions (no trigger)
> >>   but limited to 1 channel. User can set sampling frequency in this case.
> >> - INDIO_BUFFER_TRIGGERED: triggered conversions (injected with or without
> >>   scan mode, resp for one or more channels).
> >>
> >> DFSDM can use hardware triggers (e.g. STM32 timer/lptimer), add
> >> INDIO_HARDWARE_TRIGGERED to supported modes.
> >>
> >> Only support DMA-based buffer modes. In case no DMA is available, only
> >> support INDIO_DIRECT_MODE.
> >>
> >> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>  
> > 
> > Hi Fabrice,
> > 
> > I'll confess to being thoroughly confused by the many options this hardware
> > supports!  If you wouldn't mind, could you enumerate all the possible trigger
> > and mode combinations.  Even better if it includes the userspace
> > configuration that would be needed to get into a given mode.
> >   
> 
> Hi Jonathan,
> 
> Many thanks for reviewing.
> I understand... I hope I can clarify it, and give an overview.

Thanks! Definitely pointing me in the right direction.

> Basically, 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... (Maybe
> DFSDM filter 0 should be represented as trigger as well ?) I think it's
> been originally added as dt property for the audio needs.

I wonder the same question.  It might be clearer if it was explicitly set.
The only time we have done similar to here with "" as the current trigger
being valid is when we have been selecting between an internal
mode, which looks like any of your hardware triggers and
one where we are driving from an interrupt (effectively software triggered)
Here we have a whole set of different hardware triggers (which are never
exposed as interrupts as they are entirely internal) so that
"nothing" vs "explicit" switch doesn't make as much sense.
A user doesn't care about the distinction of the triggers coming from
different units on the chip and that this particular one is effectively
internal to the dfsdm.

> 
> 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.

Do we support this mode at all?  The one trigger one channel one that
is.  That is the one case I can see here that really doesn't map to
IIO concepts.  If it's all wrapped up with a hardware provided trigger
and we make sure we have exclusive use fo that trigger then of course
we can internally have anything happen.

>   - supports all triggers (software, hardware or synchronously...)
>   - no continuous conversions
> 
> b - regular
>   - supports: software triggers or synchronous with filter 0
>   - single or continuous conversions
> 
> If you like to go further in details on theses modes, there are details
> in several STM32 Ref manual (like RM0433 or RM0436 resp for STM32H743 or
> STM32MP157). This is documented under DFSDM section "Launching conversions".

Thanks for the references.  Definitely useful!  I hadn't understood for instance
that injected samples will interrupt any regular sequence - effectively
they are the higher priority option.

> 
> > There is some info in the previous patch, but I'm looking for more detail,
> > particularly around available triggers.  
> 
> From userland perspective, I'll try to summarize the various
> possibilities, that matches the array documented in previous patch:
> 
> 1 - single conversion:
> $ cd iio:deviceX # go to any filter
> $ cat in_voltageY_raw
> This uses regular conversion (not continuous)
> 
> 2 - Using sampling frequency (single channel, buffer)
> $ echo 100 > sampling_frequency

So in this case the trigger is not set to anything?
If documenting, explicitly echo "" > current_trigger
to make that clear.

> $ 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 (for filter 1..5):
> Basically, filter 0 is configured as in 2 above.

You talk about configuring filters here, but I'm not totally sure what
you mean?  Is that effectively setting the sampling frequency?

> Then other filters (e.g. 1 to 5 on stm32mp157) can be converted
> synchronously. This currently uses st,filter0-sync dt property.
> $ cd iio:deviceX # go to any filter 1..5
> $ echo 1 > scan_elements/in_voltageY_en
> $ echo 1 > buffer/enable
> This uses regular conversion, in sync with filter 0.
> 
> 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
> $ cd iio:deviceX                         # go to any filter
> $ echo 1 > scan_elements/in_voltageY_en
> $ echo tim6_trgo > trigger/current_trigger
> $ echo 1 > buffer/enable
> This basically uses injected conversion as it uses a hardware trigger
> (without scan)

Just curious, is there a benefit in doing this over setting up a 1 channel
scan?

> 
> 5 - Using a hardware trigger (with 2+ channel):
> Same as in 4/ above, but enable two or more channels in scan_elements.
> This basically uses injected conversion as it uses a hardware trigger
> (with scan mode)
> 
> 6 - In use case 4/ and 5/ above, it could be conversions on filter 1..5
> in sync with filter 0. In this case, dt property must be set currently.
> No need to set trigger.
Ah. That answers my query above. Great.
> 
> I hope it answers some of your questions,
> Please let me know if/how I should improve the documented modes in
> previous patch ?
I think this text here is very useful, so perhaps just put it in
the patch description.

> 
> Best regards,
> Fabrice
> 
> > 
> > Thanks,
> > 
> > Jonathan
> >   
> >> ---
> >>  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);
> >>    
> >