linux-kernel - Re: [PATCH 14/16] iio: adc: max1027: Consolidate the end of conversion helper

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Date:   Mon, 30 Aug 2021 11:37:16 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        linux-iio@...r.kernel.org, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/16] iio: adc: max1027: Consolidate the end of
 conversion helper

On Wed, 18 Aug 2021 13:11:37 +0200
Miquel Raynal <miquel.raynal@...tlin.com> wrote:

> Now that we have a dedicated handler for End Of Conversion interrupts,
> let's create a second path:
> - Situation 1: we are using the external hardware trigger, a conversion
>   has been triggered and the ADC pushed the data to its FIFO, we need to
>   retrieve the data and push it to the IIO buffers.
> - Situation 2: we are not using the external hardware trigger, hence we
>   are likely waiting in a blocked thread waiting for this interrupt to
>   happen: in this case we just wake up the waiting thread.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> ---
>  drivers/iio/adc/max1027.c | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
> index 8d86e77fb5db..8c5995ae59f2 100644
> --- a/drivers/iio/adc/max1027.c
> +++ b/drivers/iio/adc/max1027.c
> @@ -235,6 +235,7 @@ struct max1027_state {
>  	struct iio_trigger		*trig;
>  	__be16				*buffer;
>  	struct mutex			lock;
> +	bool				data_rdy;
>  	bool				cnvst_trigger;
>  	u8				reg ____cacheline_aligned;
>  };
> @@ -243,12 +244,22 @@ static DECLARE_WAIT_QUEUE_HEAD(max1027_queue);
>  
>  static int max1027_wait_eoc(struct iio_dev *indio_dev)
>  {
> +	struct max1027_state *st = iio_priv(indio_dev);
>  	unsigned int conversion_time = MAX1027_CONVERSION_UDELAY;
> +	int ret;
>  
> -	if (indio_dev->active_scan_mask)
> -		conversion_time *= hweight32(*indio_dev->active_scan_mask);
> +	if (st->spi->irq) {
> +		ret = wait_event_interruptible_timeout(max1027_queue,
> +						       st->data_rdy, HZ / 1000);
> +		st->data_rdy = false;
> +		if (ret == -ERESTARTSYS)
> +			return ret;
> +	} else {
> +		if (indio_dev->active_scan_mask)
> +			conversion_time *= hweight32(*indio_dev->active_scan_mask);
>  
> -	usleep_range(conversion_time, conversion_time * 2);
> +		usleep_range(conversion_time, conversion_time * 2);
> +	}
>  
>  	return 0;
>  }
> @@ -481,6 +492,9 @@ static irqreturn_t max1027_eoc_irq_handler(int irq, void *private)
>  	if (st->cnvst_trigger) {
>  		ret = max1027_read_scan(indio_dev);
>  		iio_trigger_notify_done(indio_dev->trig);
> +	} else {
> +		st->data_rdy = true;
> +		wake_up(&max1027_queue);

I can't see why a queue is appropriate for this.  Use a completion and have
one per instance of the device.  No need for the flag etc in that case as
complete() means we have had an interrupt.

>  	}
>  
>  	if (ret)