Re: [PATCH v3 06/11] iio: adc: ti-ads1015: add adequate wait time to get correct conversion

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 31 Jul 2017 00:12:50 +0900
Akinobu Mita <akinobu.mita@gmail.com> wrote:

> This driver assumes that the device is operating in the continuous
> conversion mode which performs the conversion continuously.  So this driver
> inserts a wait time before reading the conversion register if the
> configuration is changed from a previous request.
> 
> Currently, the wait time is only the period required for a single
> conversion that is calculated as the reciprocal of the sampling frequency.
> However we also need to wait for the the previous conversion to complete.
> Otherwise we probably get the conversion result for the previous
> configuration when the sampling frequency is lower.
> 
> Cc: Daniel Baluta <daniel.baluta@gmail.com>
> Cc: Jonathan Cameron <jic23@kernel.org>
> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Applied to the fixes-togreg branch of iio.git.

Unfortunately the rest of the series will have to wait for these
to work there way through Greg, to mainline and back to the iio.git
togreg branch which will take a week or two probably.

Please give me a bump if I seem to have forgotten about them.

Thanks,

Jonathan
> ---
>  drivers/iio/adc/ti-ads1015.c | 31 +++++++++++++++++++------------
>  1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti-ads1015.c b/drivers/iio/adc/ti-ads1015.c
> index 1c475e2..9c501e5 100644
> --- a/drivers/iio/adc/ti-ads1015.c
> +++ b/drivers/iio/adc/ti-ads1015.c
> @@ -242,27 +242,34 @@ static
>  int ads1015_get_adc_result(struct ads1015_data *data, int chan, int *val)
>  {
>  	int ret, pga, dr, conv_time;
> -	bool change;
> +	unsigned int old, mask, cfg;
>  
>  	if (chan < 0 || chan >= ADS1015_CHANNELS)
>  		return -EINVAL;
>  
> +	ret = regmap_read(data->regmap, ADS1015_CFG_REG, &old);
> +	if (ret)
> +		return ret;
> +
>  	pga = data->channel_data[chan].pga;
>  	dr = data->channel_data[chan].data_rate;
> +	mask = ADS1015_CFG_MUX_MASK | ADS1015_CFG_PGA_MASK |
> +		ADS1015_CFG_DR_MASK;
> +	cfg = chan << ADS1015_CFG_MUX_SHIFT | pga << ADS1015_CFG_PGA_SHIFT |
> +		dr << ADS1015_CFG_DR_SHIFT;
>  
> -	ret = regmap_update_bits_check(data->regmap, ADS1015_CFG_REG,
> -				       ADS1015_CFG_MUX_MASK |
> -				       ADS1015_CFG_PGA_MASK |
> -				       ADS1015_CFG_DR_MASK,
> -				       chan << ADS1015_CFG_MUX_SHIFT |
> -				       pga << ADS1015_CFG_PGA_SHIFT |
> -				       dr << ADS1015_CFG_DR_SHIFT,
> -				       &change);
> -	if (ret < 0)
> +	cfg = (old & ~mask) | (cfg & mask);
> +
> +	ret = regmap_write(data->regmap, ADS1015_CFG_REG, cfg);
> +	if (ret)
>  		return ret;
>  
> -	if (change || data->conv_invalid) {
> -		conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]);
> +	if (old != cfg || data->conv_invalid) {
> +		int dr_old = (old & ADS1015_CFG_DR_MASK) >>
> +				ADS1015_CFG_DR_SHIFT;
> +
> +		conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr_old]);
> +		conv_time += DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]);
>  		usleep_range(conv_time, conv_time + 1);
>  		data->conv_invalid = false;
>  	}