linux-kernel - Re: [PATCH v2 2/2] iio: adc: ti-ads8344: optimize consumption

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Date:   Sat, 18 Apr 2020 16:13:22 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Gregory CLEMENT <gregory.clement@...tlin.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] iio: adc: ti-ads8344: optimize consumption

On Thu, 16 Apr 2020 22:54:28 +0200
Alexandre Belloni <alexandre.belloni@...tlin.com> wrote:

> Set the clock mode only once, at probe time and then keep the ADC powered
> down between conversions.
> 
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
Looks fine to me. I'd like to be lazy and not take this until the fix is
in my upstream (even though I suspect the merge would be fine).

Give me a poke if I seem to have forgotten this after that is true!

Thanks,

Jonathan

> ---
>  drivers/iio/adc/ti-ads8344.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti-ads8344.c b/drivers/iio/adc/ti-ads8344.c
> index abe4b56c847c..40e7a9eee189 100644
> --- a/drivers/iio/adc/ti-ads8344.c
> +++ b/drivers/iio/adc/ti-ads8344.c
> @@ -72,7 +72,7 @@ static const struct iio_chan_spec ads8344_channels[] = {
>  };
>  
>  static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
> -				  bool differential)
> +				  bool differential, u8 clock)
>  {
>  	struct spi_device *spi = adc->spi;
>  	int ret;
> @@ -81,7 +81,7 @@ static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
>  	if (!differential)
>  		adc->tx_buf |= ADS8344_SINGLE_END;
>  	adc->tx_buf |= ADS8344_CHANNEL(channel);
> -	adc->tx_buf |= ADS8344_CLOCK_INTERNAL;
> +	adc->tx_buf |= clock;
>  
>  	ret = spi_write(spi, &adc->tx_buf, 1);
>  	if (ret)
> @@ -106,7 +106,7 @@ static int ads8344_read_raw(struct iio_dev *iio,
>  	case IIO_CHAN_INFO_RAW:
>  		mutex_lock(&adc->lock);
>  		*value = ads8344_adc_conversion(adc, channel->scan_index,
> -						channel->differential);
> +						channel->differential, 0);
>  		mutex_unlock(&adc->lock);
>  		if (*value < 0)
>  			return *value;
> @@ -161,6 +161,11 @@ static int ads8344_probe(struct spi_device *spi)
>  	if (ret)
>  		return ret;
>  
> +	/* Do a dummy read and set external clock mode */
> +	ret = ads8344_adc_conversion(adc, 0, 0, ADS8344_CLOCK_INTERNAL);
> +	if (ret < 0)
> +		return ret;
> +
>  	spi_set_drvdata(spi, indio_dev);
>  
>  	ret = iio_device_register(indio_dev);