linux-kernel - RE: [PATCH 12/16] iio: adc: max1027: Introduce an end of conversion helper

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Message-ID: <SJ0PR03MB635976F76F5121FFF26E858B99C19@SJ0PR03MB6359.namprd03.prod.outlook.com>
Date:   Fri, 20 Aug 2021 07:28:17 +0000
From:   "Sa, Nuno" <Nuno.Sa@...log.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>
CC:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 12/16] iio: adc: max1027: Introduce an end of conversion
 helper



> -----Original Message-----
> From: Miquel Raynal <miquel.raynal@...tlin.com>
> Sent: Wednesday, August 18, 2021 1:12 PM
> To: Jonathan Cameron <jic23@...nel.org>; Lars-Peter Clausen
> <lars@...afoo.de>
> Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>; linux-
> iio@...r.kernel.org; linux-kernel@...r.kernel.org; Miquel Raynal
> <miquel.raynal@...tlin.com>
> Subject: [PATCH 12/16] iio: adc: max1027: Introduce an end of
> conversion helper
> 
> [External]
> 
> For now this helper only waits for the maximum duration of a
> conversion,
> but it will soon be improved to properly handle the end of conversion
> interrupt.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> ---
>  drivers/iio/adc/max1027.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
> index afc3ce69f7ea..2d6485591761 100644
> --- a/drivers/iio/adc/max1027.c
> +++ b/drivers/iio/adc/max1027.c
> @@ -60,6 +60,9 @@
>  #define MAX1027_NAVG_32   (0x03 << 2)
>  #define MAX1027_AVG_EN    BIT(4)
> 
> +/* Device can achieve 300ksps so we assume a 3.33us conversion
> delay */
> +#define MAX1027_CONVERSION_UDELAY 4
> +
>  enum max1027_id {
>  	max1027,
>  	max1029,
> @@ -236,6 +239,20 @@ struct max1027_state {
>  	u8				reg ____cacheline_aligned;
>  };
> 
> +static DECLARE_WAIT_QUEUE_HEAD(max1027_queue);
> +
> +static int max1027_wait_eoc(struct iio_dev *indio_dev)
> +{
> +	unsigned int conversion_time =
> MAX1027_CONVERSION_UDELAY;
> +
> +	if (indio_dev->active_scan_mask)
> +		conversion_time *= hweight32(*indio_dev-
> >active_scan_mask);
> +
> +	usleep_range(conversion_time, conversion_time * 2);
> +
> +	return 0;
> +}
> +
>  /* Scan from 0 to the highest requested channel */
>  static int max1027_configure_chans_to_scan(struct iio_dev
> *indio_dev)
>  {
> @@ -310,9 +327,11 @@ static int max1027_read_single_value(struct
> iio_dev *indio_dev,
>  	/*
>  	 * For an unknown reason, when we use the mode "10" (write
>  	 * conversion register), the interrupt doesn't occur every time.
> -	 * So we just wait 1 ms.
> +	 * So we just wait the maximum conversion time and deliver
> the value.
>  	 */
> -	mdelay(1);
> +	ret = max1027_wait_eoc(indio_dev);
> +	if (ret)
> +		return ret;

I'm a bit confused here... Why are we looking at the active_scan_mask?
Aren't we preventing this for running concurrently with buffering?

- Nuno Sá
> 
>  	/* Read result */
>  	ret = spi_read(st->spi, st->buffer, (chan->type == IIO_TEMP) ?
> 4 : 2);
> --
> 2.27.0