linux-kernel - Re: [PATCH v1 2/3] iio: ABI: adc: ad4130: document filter_mode{,

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Date:   Sat, 16 Apr 2022 16:02:22 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Cosmin Tanislav <demonsingur@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-iio@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Cosmin Tanislav <cosmin.tanislav@...log.com>
Subject: Re: [PATCH v1 2/3] iio: ABI: adc: ad4130: document
 filter_mode{,_available}

On Wed, 13 Apr 2022 12:40:10 +0300
Cosmin Tanislav <demonsingur@...il.com> wrote:

> AD4130-8 is an ultra-low power, high precision,
> measurement solution for low bandwidth battery
> operated applications.
> 
> The fully integrated AFE (Analog Front-End)
> includes a multiplexer for up to 16 single-ended
> or 8 differential inputs, PGA (Programmable Gain
> Amplifier), 24-bit Sigma-Delta ADC, on-chip
> reference and oscillator, selectable filter
> options, smart sequencer, sensor biasing and
> excitation options, diagnostics, and a FIFO
> buffer.
> 
> Signed-off-by: Cosmin Tanislav <cosmin.tanislav@...log.com>
> ---
>  .../ABI/testing/sysfs-bus-iio-adc-ad4130      | 36 +++++++++++++++++++
>  1 file changed, 36 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-ad4130
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-ad4130 b/Documentation/ABI/testing/sysfs-bus-iio-adc-ad4130
> new file mode 100644
> index 000000000000..942150991e75
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-ad4130
> @@ -0,0 +1,36 @@
> +What:		/sys/bus/iio/devices/iio:deviceX/in_voltage-voltage_filter_mode_available
> +KernelVersion:

Make a guess at the kernel version (hopefully this cycle!)
We never remember to fill these in later so better to have it slightly wrong
than not present at all.

> +Contact:	linux-iio@...r.kernel.org
> +Description:
> +		Reading returns a list with the possible filter modes.
> +		"sinc4"       - Sinc 4. Excellent noise performance. Long 1st
> +				conversion time. No natural 50/60Hz rejection.
> +		"sinc4+sinc1" - Sinc4 + averaging by 8. Low 1st conversion time.
> +		"sinc3"	      - Sinc3. Moderate 1st conversion time. Good noise
> +				performance.
> +		"sinc3+rej60" - Sinc3 + 60Hz rejection. At a sampling frequency
> +				of 50Hz, achieves simultaneous 50Hz and 60Hz
> +				rejection.
> +		"sinc3+sinc1" - Sinc3 + averaging by 8. Low 1st conversion time.
> +				Best used with a sampling frequency of at least
> +				216.19Hz.
> +		"sinc3+pf1"   - Sinc3 + Post Filter 1.
> +				53dB rejection @ 50Hz, 58dB rejection @ 60Hz.
> +		"sinc3+pf2"   - Sinc3 + Post Filter 2.
> +				70dB rejection @ 50Hz, 70dB rejection @ 60Hz.
> +		"sinc3+pf3"   - Sinc3 + Post Filter 3.
> +				99dB rejection @ 50Hz, 103dB rejection @ 60Hz.
> +		"sinc3+pf4"   - Sinc3 + Post Filter 4.
> +				103dB rejection @ 50Hz, 109dB rejection @ 60Hz.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY-voltageZ_filter_mode
> +KernelVersion:
> +Contact:	linux-iio@...r.kernel.org
> +Description:
> +		Set the filter mode of the differential channel. When the filter
> +		mode changes, the in_voltageY-voltageZ_sampling_frequency and
> +		in_voltageY-voltageZ_sampling_frequency_available attributes
> +		might also change to accomodate the new filter mode.
> +		If the current sampling frequency is out of range for the new
> +		filter mode, the sampling frequency will be changed to the
> +		closest valid one.