Re: [PATCH v3 3/3] iio: adc: Fix incorrect reading when datarate changed in single mode

[David Lechner <dlechner@baylibre.com>]

On 6/13/26 2:09 PM, Jakub Szczudlo wrote:
> When device is suspended and it is in single mode then changing
> datarate doesn't make it actual wait for new measurement, so to

s/actual/actually/

> be sure that read after change is correct functions that changes
> datarate and gain will wait for new data.

s/datarate/data rate/g


The commit message isn't very clear to me. Is the point that the
changes don't actually take effect in the ADC until a conversion
is done?

> 
> Signed-off-by: Jakub Szczudlo <jakubszczudlo40@gmail.com>
> ---
>  drivers/iio/adc/ti-ads1100.c | 55 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 52 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti-ads1100.c b/drivers/iio/adc/ti-ads1100.c
> index 76de2466dc53..195394665cd1 100644
> --- a/drivers/iio/adc/ti-ads1100.c
> +++ b/drivers/iio/adc/ti-ads1100.c
> @@ -123,6 +123,36 @@ static int ads1100_get_voltage_microvolts(struct ads1100_data *data)
>  	return ads1100_get_voltage_milivolts(data) * MICRO / MILLI;
>  }
>  
> +static bool ads1100_new_data_ready(struct ads1100_data *data)
> +{
> +	int ret;
> +	u8 buffer[3];
> +
> +	ret = i2c_master_recv(data->client, (char *)&buffer, sizeof(buffer));
> +	if (ret < 3) {
> +		dev_err(&data->client->dev, "I2C read fail: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return FIELD_GET(ADS1100_CFG_ST_BSY, buffer[2]);
> +}
> +
> +static int ads1100_poll_data_ready(struct ads1100_data *data)
> +{
> +	u8 buffer[3];
> +	bool data_ready;
> +	int datarate = data->ads_config->data_rate[FIELD_GET(ADS1100_DR_MASK, data->config)];
> +   // To be sure we wait 5 times more than datarate
> +	unsigned long wait_time = DIV_ROUND_CLOSEST(MICRO, 5 * datarate);
> +
> +	/* To be sure that polled value will have value after config change */
> +	i2c_master_recv(data->client, (char *)&buffer, sizeof(buffer));
> +
> +	return read_poll_timeout(ads1100_new_data_ready, data_ready,
> +				 !data_ready, wait_time,
> +				 ADS1100_MAX_DRDY_TIMEOUT, false, data);
> +}
> +
>  static int ads1100_data_bits(struct ads1100_data *data)
>  {
>  	return ads1100_data_rate_bits[FIELD_GET(ADS1100_DR_MASK, data->config)];
> @@ -165,6 +194,7 @@ static int ads1100_set_scale(struct ads1100_data *data, int val, int val2)
>  {
>  	int microvolts;
>  	int gain;
> +	int ret;
>  
>  	/* With Vdd between 2.7 and 5V, the scale is always below 1 */
>  	if (val)
> @@ -185,21 +215,40 @@ static int ads1100_set_scale(struct ads1100_data *data, int val, int val2)
>  	if (gain < BIT(0) || gain > BIT(3))
>  		return -EINVAL;
>  
> +	ret = pm_runtime_resume_and_get(&data->client->dev);
> +	if (ret < 0)
> +		return ret;
> +
>  	ads1100_set_config_bits(data, ADS1100_PGA_MASK, ffs(gain) - 1);
>  
> -	return 0;
> +	ret = ads1100_poll_data_ready(data);
> +
> +	pm_runtime_put_autosuspend(&data->client->dev);
> +
> +	return ret;
>  }
>  
>  static int ads1100_set_data_rate(struct ads1100_data *data, int chan, int rate)
>  {
>  	unsigned int i;
>  	unsigned int size;
> +	int ret;
>  
>  	size = data->supports_data_rate ? ARRAY_SIZE(ads1100_data_rate) : 1;
>  	for (i = 0; i < size; i++) {
> -		if (data->ads_config->data_rate[i] == rate)
> -			return ads1100_set_config_bits(data, ADS1100_DR_MASK,
> +		if (data->ads_config->data_rate[i] != rate)
> +			continue;
> +
> +		ret = pm_runtime_resume_and_get(&data->client->dev);
> +		if (ret < 0)
> +			return ret;
> +
> +		ads1100_set_config_bits(data, ADS1100_DR_MASK,
>  					FIELD_PREP(ADS1100_DR_MASK, i));

Why no longer checking the return value of ads1100_set_config_bits()?

> +		ret = ads1100_poll_data_ready(data);
> +
> +		pm_runtime_put_autosuspend(&data->client->dev);
> +		return ret;
>  	}
>  
>  	return -EINVAL;