On Wed, 2024-05-01 at 16:55 +0200, Julien Stephan wrote: > Adds support for rolling average oversampling mode. > > Rolling oversampling mode uses a first in, first out (FIFO) buffer of > the most recent samples in the averaging calculation, allowing the ADC > throughput rate and output data rate to stay the same, since we only need > to take only one sample for each new conversion. > > The FIFO length is 8, thus the available oversampling ratios are 1, 2, 4, 8 > in this mode (vs 1, 2, 4, 8, 16, 32 for the normal average) > > In order to be able to change the averaging mode, this commit also adds > the new "oversampling_mode" and "oversampling_mode_available" custom > attributes along with the according documentation file in > Documentation/ABI/testing/sysfs-bus-iio-adc-ad7380 since no standard > attributes correspond to this use case. > > Signed-off-by: Julien Stephan <jstephan@xxxxxxxxxxxx> > --- > Documentation/ABI/testing/sysfs-bus-iio-adc-ad7380 | 38 ++++++ > MAINTAINERS | 1 + > drivers/iio/adc/ad7380.c | 143 +++++++++++++++++++-- > 3 files changed, 174 insertions(+), 8 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-ad7380 > b/Documentation/ABI/testing/sysfs-bus-iio-adc-ad7380 > new file mode 100644 > index 000000000000..0a560ef3e32a > --- /dev/null > +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-ad7380 > @@ -0,0 +1,38 @@ > +What: /sys/bus/iio/devices/iio:deviceX/oversampling_mode > +KernelVersion: 6.9 > +Contact: Michael Hennerich <michael.hennerich@xxxxxxxxxx> > +Description: > + Writing this attribute sets the oversampling average mode. > + Reading it, shows the configured mode. > + Available modes can be displayed using the oversampling_mode_available > + attribute. > + When writing this attribute to change the oversampling mode, this will > + have the following side effects: > + > + - soft reset the ADC to flush the oversampling block and FIFO > + > + - the available oversampling ratios depend on the oversampling mode > + configured so to avoid misconfiguration, changing the mode will disable > + the oversampling by setting the ratio to 1. Hmm, can we somehow re-enable it again with a proper configuration (after the mode change)? > + > + - the list of available ratios (displayed by reading the > + oversampling_ratio_available attribute) will be updated when changing > + the oversampling mode. > + > +What: /sys/bus/iio/devices/iio:deviceX/oversampling_mode_available > +KernelVersion: 6.9 > +Contact: Michael Hennerich <michael.hennerich@xxxxxxxxxx> > +Description: > + Display the available oversampling average modes. The two available modes > + are "normal" and "rolling" where "normal" average mode is the default one. > + > + - normal averaging involves taking a number of samples, adding them > + together, and dividing the result by the number of samples taken. > + This result is then output from the device. The sample data is cleared > + when the process completes. Because we need more samples to output a > + value, the data output rate decrease with the oversampling ratio. > + > + - rolling oversampling mode uses a first in, first out (FIFO) buffer of > + the most recent samples in the averaging calculation, allowing the ADC > + throughput rate and output data rate to stay the same, since we only need > + to take only one sample for each new conversion. > diff --git a/MAINTAINERS b/MAINTAINERS > index 87724a9e9f9f..ca1e115f2aff 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -434,6 +434,7 @@ R: David Lechner <dlechner@xxxxxxxxxxxx> > S: Supported > W: > https://wiki.analog.com/resources/tools-software/linux-drivers/iio-adc/ad738x > W: https://ez.analog.com/linux-software-drivers > +F: Documentation/ABI/testing/sysfs-bus-iio-adc-ad7380 > F: Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml > F: drivers/iio/adc/ad7380.c > > diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c > index 1e3869f5e48c..7b021bb9cf87 100644 > --- a/drivers/iio/adc/ad7380.c > +++ b/drivers/iio/adc/ad7380.c > @@ -51,6 +51,8 @@ > #define AD7380_REG_ADDR_ALERT_HIGH_TH 0x5 > > #define AD7380_CONFIG1_OS_MODE BIT(9) > +#define OS_MODE_NORMAL_AVERAGE 0 > +#define OS_MODE_ROLLING_AVERAGE 1 no AD7380 prefix? > #define AD7380_CONFIG1_OSR GENMASK(8, 6) > #define AD7380_CONFIG1_CRC_W BIT(5) > #define AD7380_CONFIG1_CRC_R BIT(4) > @@ -159,16 +161,27 @@ static const struct ad7380_timing_specs ad7380_4_timing = { > .t_csh_ns = 20, > }; > ... > > +static ssize_t oversampling_mode_store(struct device *dev, > + struct device_attribute *attr, > + const char *buf, size_t len) > +{ > + struct iio_dev *indio_dev = dev_to_iio_dev(dev); > + struct ad7380_state *st = iio_priv(indio_dev); > + int os_mode, ret; > + > + ret = sysfs_match_string(ad7380_oversampling_average_modes, buf); > + if (ret < 0) > + return ret; > + > + os_mode = ret; > + > + iio_device_claim_direct_scoped(return -EBUSY, indio_dev) { > + ret = regmap_update_bits(st->regmap, AD7380_REG_ADDR_CONFIG1, > + AD7380_CONFIG1_OS_MODE, > + FIELD_PREP(AD7380_CONFIG1_OS_MODE, > os_mode)); > + > + if (ret) > + return ret; > + > + st->oversampling_mode = os_mode; > + > + /* > + * Oversampling ratio depends on oversampling mode, to avoid > + * misconfiguration when changing oversampling mode, > + * disable oversampling by setting OSR to 0. > + */ Given the comment, I would expect you to disable osr before changing the mode. > + ret = regmap_update_bits(st->regmap, AD7380_REG_ADDR_CONFIG1, > + AD7380_CONFIG1_OSR, > FIELD_PREP(AD7380_CONFIG1_OSR, 0)); > + > + if (ret) > + return ret; > + > + st->oversampling_ratio = 1; > + 1? Also, it would be nice if we could re-enabled osr. So the flow would maybe be: 1) disable osr; 2) change mode; 3) do whatever we need so configuration makes sense for new mode? 4) re-enable osr; 5) soft-reset; Also not sure if 4) and 5) are in the correct order. > + /* > + * Perform a soft reset. > + * This will flush the oversampling block and FIFO but will > + * maintain the content of the configurable registers. > + */ > + ret = regmap_update_bits(st->regmap, AD7380_REG_ADDR_CONFIG2, > + AD7380_CONFIG2_RESET, > + FIELD_PREP(AD7380_CONFIG2_RESET, > + AD7380_CONFIG2_RESET_SOFT)); > + } > + return ret ?: len; > +} > + > +static ssize_t oversampling_mode_available_show(struct device *dev, > + struct device_attribute *attr, > char *buf) > +{ > + int i; > + size_t len = 0; > + > + for (i = 0; i < ARRAY_SIZE(ad7380_oversampling_average_modes); i++) > + len += sysfs_emit_at(buf, len, "%s ", > ad7380_oversampling_average_modes[i]); > + > + buf[len - 1] = '\n'; > + > + return len; > +} > + > +static IIO_DEVICE_ATTR_RW(oversampling_mode, 0); > +static IIO_DEVICE_ATTR_RO(oversampling_mode_available, 0); > + > +static struct attribute *ad7380_attributes[] = { > + &iio_dev_attr_oversampling_mode.dev_attr.attr, > + &iio_dev_attr_oversampling_mode_available.dev_attr.attr, > + NULL > +}; > + Maybe use IIO_ENUM... It allows the core to do some of the stuff you're doing for you. - Nuno Sá
