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SubjectRe: [PATCH v2 7/7] iio: adc: ina2xx: Actually align the loop with the conversion ready flag
On Thu, 21 Dec 2017 19:31:38 +0100
Stefan Brüns <stefan.bruens@rwth-aachen.de> wrote:

> Currently, the registers are read out once per conversion interval. If
> the reading is delayed as the conversion has not yet finished, this extra
> time is treated as being part of the readout, although it should delay
> the start of the poll interval. This results in the interval starting
> slightly earlier in each iteration, until all time between reads is
> spent polling the status registers instead of sleeping.
>
> To fix this, the delay has to account for the state of the conversion
> ready flag. Whenever the conversion is already finished, schedule the next
> read on the regular interval, otherwise schedule it one interval after the
> flag bit has been set.
>
> Split the work function in two functions, one for the status poll and one
> for reading the values, to be able to note down the time when the flag
> bit is raised.
>
> Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Great thanks.

Applied to the togreg branch of iio.git and pushed out as testing
for the autobuilders to play with it.

Thanks,

Jonathan

>
> ---
>
> Changes in v2:
> - Describe old behaviour in commit message more clearly
>
> drivers/iio/adc/ina2xx-adc.c | 57 +++++++++++++++++++++++++++++---------------
> 1 file changed, 38 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c
> index b7407ac91b59..80af0d2322a3 100644
> --- a/drivers/iio/adc/ina2xx-adc.c
> +++ b/drivers/iio/adc/ina2xx-adc.c
> @@ -697,13 +697,10 @@ static const struct iio_chan_spec ina219_channels[] = {
> IIO_CHAN_SOFT_TIMESTAMP(4),
> };
>
> -static int ina2xx_work_buffer(struct iio_dev *indio_dev)
> +static int ina2xx_conversion_ready(struct iio_dev *indio_dev)
> {
> struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> - /* data buffer needs space for channel data and timestap */
> - unsigned short data[4 + sizeof(s64)/sizeof(short)];
> - int bit, ret, i = 0;
> - s64 time;
> + int ret;
> unsigned int alert;
>
> /*
> @@ -717,22 +714,29 @@ static int ina2xx_work_buffer(struct iio_dev *indio_dev)
> * For now, we do an extra read of the MASK_ENABLE register (INA226)
> * resp. the BUS_VOLTAGE register (INA219).
> */
> - if (!chip->allow_async_readout)
> - do {
> - if (chip->config->chip_id == ina226) {
> - ret = regmap_read(chip->regmap,
> - INA226_MASK_ENABLE, &alert);
> - alert &= INA226_CVRF;
> - } else {
> - ret = regmap_read(chip->regmap,
> - INA2XX_BUS_VOLTAGE, &alert);
> - alert &= INA219_CNVR;
> - }
> + if (chip->config->chip_id == ina226) {
> + ret = regmap_read(chip->regmap,
> + INA226_MASK_ENABLE, &alert);
> + alert &= INA226_CVRF;
> + } else {
> + ret = regmap_read(chip->regmap,
> + INA2XX_BUS_VOLTAGE, &alert);
> + alert &= INA219_CNVR;
> + }
>
> - if (ret < 0)
> - return ret;
> + if (ret < 0)
> + return ret;
>
> - } while (!alert);
> + return !!alert;
> +}
> +
> +static int ina2xx_work_buffer(struct iio_dev *indio_dev)
> +{
> + struct ina2xx_chip_info *chip = iio_priv(indio_dev);
> + /* data buffer needs space for channel data and timestap */
> + unsigned short data[4 + sizeof(s64)/sizeof(short)];
> + int bit, ret, i = 0;
> + s64 time;
>
> time = iio_get_time_ns(indio_dev);
>
> @@ -776,6 +780,21 @@ static int ina2xx_capture_thread(void *data)
> ktime_get_ts64(&next);
>
> do {
> + while (!chip->allow_async_readout) {
> + ret = ina2xx_conversion_ready(indio_dev);
> + if (ret < 0)
> + return ret;
> +
> + /*
> + * If the conversion was not yet finished,
> + * reset the reference timestamp.
> + */
> + if (ret == 0)
> + ktime_get_ts64(&next);
> + else
> + break;
> + }
> +
> ret = ina2xx_work_buffer(indio_dev);
> if (ret < 0)
> return ret;

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