Re: [PATCH 12/16] iio: adc: max1027: Introduce an end of conversion helper

From: Jonathan Cameron <jic23@kernel.org>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	linux-iio@vger.kernel.org, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 12/16] iio: adc: max1027: Introduce an end of conversion helper
Date: Mon, 30 Aug 2021 11:34:57 +0100	[thread overview]
Message-ID: <20210830113457.4acf12e2@jic23-huawei> (raw)
In-Reply-To: <20210818111139.330636-13-miquel.raynal@bootlin.com>

On Wed, 18 Aug 2021 13:11:35 +0200
Miquel Raynal <miquel.raynal@bootlin.com> wrote:

> 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@bootlin.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);
Why here?  This had me confused when I couldn't find it being introduced
in the later patch that uses it.  More comments in that patch.

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