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Re: [PATCH v3 2/2] iio: ina2xx: provide a sysfs parameter to allow async readout of the ADCs

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  Re: [PATCH v3 2/2] iio: ina2xx: provide a sysfs parameter to allow  async readout of the ADCs Jonathan Cameron <jic23@kernel.org> - 2015-12-12 17:00 +0100
    [PATCH] iio: ina2xx: add ABI documentation entry sysfs-bus-iio-ina2xx-adc Marc Titinger <mtitinger@baylibre.com> - 2015-12-14 12:10 +0100

#1290217 — Re: [PATCH v3 2/2] iio: ina2xx: provide a sysfs parameter to allow async readout of the ADCs

On 07/12/15 09:09, Marc Titinger wrote:
> This can lead to repeated or skipped samples depending on the clock beat
> between the capture thread and the chip sampling clock, but will also spare
> reading/waiting for the Capture Ready Flag and improve the available i2c
> bandwidth for reading measurements.
> 
> Output of iio_info:
> ...snip...
> 4 device-specific attributes found:
>   attr 0: in_oversampling_ratio value: 4
>   attr 1: in_allow_async_readout value: 0
>   attr 2: integration_time_available value: 140 204 332 588 1100 2116...
>   attr 3: in_sampling_frequency value: 114
> 
> Signed-off-by: Marc Titinger <mtitinger@baylibre.com>
Applied to the togreg branch of iio.git - initially pushed out as testing for the autobuilders
to play with it.

Could you prepare a follow up patch adding abi docs to
Documentation/ABI/testing/sysfs-bus-iio-ina2xx-adc 
please.

I didn't want to hold this up by insisting on docs now, but it does need
doing asap.

Jonathan
> ---
>  drivers/iio/adc/ina2xx-adc.c | 54 ++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 45 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c
> index 0e7c474..615c203 100644
> --- a/drivers/iio/adc/ina2xx-adc.c
> +++ b/drivers/iio/adc/ina2xx-adc.c
> @@ -111,6 +111,7 @@ struct ina2xx_chip_info {
>  	s64 prev_ns;	/* track buffer capture time, check for underruns*/
>  	int int_time_vbus; /* Bus voltage integration time uS */
>  	int int_time_vshunt; /* Shunt voltage integration time uS */
> +	bool allow_async_readout;
>  };
>  
>  static const struct ina2xx_config ina2xx_config[] = {
> @@ -326,6 +327,33 @@ _err:
>  }
>  
>  
> +static ssize_t ina2xx_allow_async_readout_show(struct device *dev,
> +					   struct device_attribute *attr,
> +					   char *buf)
> +{
> +	struct ina2xx_chip_info *chip = iio_priv(dev_to_iio_dev(dev));
> +
> +	return sprintf(buf, "%d\n", chip->allow_async_readout);
> +}
> +
> +static ssize_t ina2xx_allow_async_readout_store(struct device *dev,
> +				struct device_attribute *attr,
> +				const char *buf, size_t len)
> +{
> +	struct ina2xx_chip_info *chip = iio_priv(dev_to_iio_dev(dev));
> +	bool val;
> +	int ret;
> +
> +	ret = strtobool((const char *) buf, &val);
> +	if (ret)
> +		return ret;
> +
> +	chip->allow_async_readout = val;
> +
> +	return len;
> +}
> +
> +
>  #define INA2XX_CHAN(_type, _index, _address) { \
>  	.type = (_type), \
>  	.address = (_address), \
> @@ -392,16 +420,17 @@ static int ina2xx_work_buffer(struct iio_dev *indio_dev)
>  	 * GPIO a triggered buffer could be used instead.
>  	 * For now, we pay for that extra read of the ALERT register
>  	 */
> -	do {
> -		ret = regmap_read(chip->regmap, INA226_ALERT_MASK,
> -				  &alert);
> -		if (ret < 0)
> -			return ret;
> +	if (!chip->allow_async_readout)
> +		do {
> +			ret = regmap_read(chip->regmap, INA226_ALERT_MASK,
> +					  &alert);
> +			if (ret < 0)
> +				return ret;
>  
> -		alert &= INA266_CVRF;
> -		trace_printk("Conversion ready: %d\n", !!alert);
> +			alert &= INA266_CVRF;
> +			trace_printk("Conversion ready: %d\n", !!alert);
>  
> -	} while (!alert);
> +		} while (!alert);
>  
>  	/*
>  	 * Single register reads: bulk_read will not work with ina226
> @@ -446,7 +475,8 @@ static int ina2xx_capture_thread(void *data)
>  	 * Poll a bit faster than the chip internal Fs, in case
>  	 * we wish to sync with the conversion ready flag.
>  	 */
> -	sampling_us -= 200;
> +	if (!chip->allow_async_readout)
> +		sampling_us -= 200;
>  
>  	do {
>  		buffer_us = ina2xx_work_buffer(indio_dev);
> @@ -471,6 +501,7 @@ int ina2xx_buffer_enable(struct iio_dev *indio_dev)
>  		     1000000/sampling_us, chip->avg);
>  
>  	trace_printk("Expected work period: %u us\n", sampling_us);
> +	trace_printk("Async readout mode: %d\n", chip->allow_async_readout);
>  
>  	chip->prev_ns = iio_get_time_ns();
>  
> @@ -512,7 +543,12 @@ static int ina2xx_debug_reg(struct iio_dev *indio_dev,
>  static IIO_CONST_ATTR_INT_TIME_AVAIL \
>   ("0.000140 0.000204 0.000332 0.000588 0.001100 0.002116 0.004156 0.008244");
>  
> +static IIO_DEVICE_ATTR(in_allow_async_readout, S_IRUGO | S_IWUSR,
> +		       ina2xx_allow_async_readout_show,
> +		       ina2xx_allow_async_readout_store, 0);
> +
>  static struct attribute *ina2xx_attributes[] = {
> +	&iio_dev_attr_in_allow_async_readout.dev_attr.attr,
>  	&iio_const_attr_integration_time_available.dev_attr.attr,
>  	NULL,
>  };
> 

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#1291112 — [PATCH] iio: ina2xx: add ABI documentation entry sysfs-bus-iio-ina2xx-adc

Documentation for attributes:

 * in_allow_async_readout
 * in_shunt_resistor

Signed-off-by: Marc Titinger <mtitinger@baylibre.com>
---
 Documentation/ABI/testing/sysfs-bus-iio-ina2xx-adc | 24 ++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-ina2xx-adc

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-ina2xx-adc b/Documentation/ABI/testing/sysfs-bus-iio-ina2xx-adc
new file mode 100644
index 0000000..8916f7e
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-ina2xx-adc
@@ -0,0 +1,24 @@
+What:		/sys/bus/iio/devices/iio:deviceX/in_allow_async_readout
+Date:		December 2015
+KernelVersion:	4.4
+Contact:	linux-iio@vger.kernel.org
+Description:
+		By default (value '0'), the capture thread checks for the Conversion
+		Ready Flag to being set prior to committing a new value to the sample
+		buffer. This synchronizes the in-chip conversion rate with the
+		in-driver readout rate at the cost of an additional register read.
+
+		Writing '1' will remove the polling for the Conversion Ready Flags to
+		save the additional i2c transaction, which will improve the bandwidth
+		available for reading data. However, samples can be occasionally skipped
+		or repeated, depending on the beat between the capture and conversion
+		rates.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_shunt_resistor
+Date:		December 2015
+KernelVersion:	4.4
+Contact:	linux-iio@vger.kernel.org
+Description:
+		The value of the shunt resistor may be known only at runtime fom an
+		eeprom content read by a client application. This attribute allows to
+		set its value in ohms.
-- 
1.9.1

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