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

From: Jonathan Cameron <[email-masked]>
Date: Mon, 23 Dec 2019 12:28:38 +0000

On Wed, 18 Dec 2019 16:24:02 +0000
<[email-masked]> wrote:

> From: Eugen Hristev <[email-masked]>
> 
> 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 <[email-masked]>
Minor points inline.

Thanks,

Jonathan

> ---
>  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) && \

This increasingly feels like it should be a function with clearly
passed parameters rather than macro fun.

> +		!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);

Hmm. This is a bit nasty but I guess we can't avoid it.

> +	}
>  
>  	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

External trigger is a bit of a generic name - sounds like one coming from
'somewhere else'.  Perhaps "External trigger in the ADC .." or similar?

> +	 * 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);

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