linux-kernel - Re: [PATCH v2] Documentation: ABI: add oversampling frequency in sysfs-bus-iio

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Message-ID: <6rgtuq2mtk3a63d3tlzbgjhauslkztgemn7566qyi3mzwywprq@lxhsvwofnvg2>
Date: Tue, 22 Apr 2025 09:30:33 +0200
From: Jorge Marques <gastmaier@...il.com>
To: Jonathan Cameron <jic23@...nel.org>, dlechner@...libre.com
Cc: Jorge Marques <jorge.marques@...log.com>, 
	Lars-Peter Clausen <lars@...afoo.de>, Michael.Hennerich@...log.com, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Documentation: ABI: add oversampling frequency in
 sysfs-bus-iio

Hi Jonathan, David

Should this patch be submitted differently, such as under the AD4052 V2
series? Or are further modifications needed?

Regards,
Jorge

On Tue, Apr 08, 2025 at 10:20:29AM +0200, Jorge Marques wrote:
> Some devices have an internal clock used to space out the conversion
> trigger for the oversampling filter,
> Consider an ADC with conversion and data ready pins topology:
> 
>   Sampling trigger |       |       |       |       |
>   ADC conversion   ++++    ++++    ++++    ++++    ++++
>   ADC data ready      *       *       *       *       *
> 
> With the oversampling frequency, conversions are spaced:
> 
>   Sampling trigger |       |       |       |       |
>   ADC conversion   + + + + + + + + + + + + + + + + + + + +
>   ADC data ready         *       *       *       *       *
> 
> In some devices and ranges, this internal clock can be used to evenly
> space the conversions between the sampling edge.
> In other devices the oversampling frequency is fixed or is computed
> based on the sampling frequency parameter, and the parameter is
> read only.
> 
> Signed-off-by: Jorge Marques <jorge.marques@...log.com>
> ---
> Some device families such as Analog Device's max1363, ad7606, ad799x, and
> ad4052 contain internal clocks used by monitor modes and oversampling.
> Devices' monitor modes are exposed as IIO events.
> The max1363 driver included the events/sampling_frequency in
> commit 168c9d95a940 ("iio:adc:max1363 move from staging.")
> and ad799x in
> commit ba1d79613df3 ("staging:iio:ad799x: Use event spec for threshold
> hysteresis")
> but went undocumented so far.
> 
> The oversampling sampling frequency is a planned feature to be patched
> onto the ad7606 driver.
> In this particular device, it is called oversampling padding.
> The upcoming ad4052 linux driver will utilize both entries,
> it is worth noting, however, there is a single register for both
> options. Since the device is never concurrently in both modes, the
> values will be safely cached on the device state.
> ---
> Changes in v2:
> - Updated oversampling frequency description according to discussion 
> - Don't include already applied
>   commit 3a8fee68faf2 ("Documentation: ABI: add events sampling frequency in sysfs-bus-iio")
> - Link to v1: https://lore.kernel.org/r/20250321-abi-oversampling-events-frequency-v1-0-794c1ab2f079@analog.com
> ---
>  Documentation/ABI/testing/sysfs-bus-iio | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> index 722aa989baac43f694076074b307d134867b4533..6f5c4060704742ae5f5672a861271b88084ac8f8 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio
> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> @@ -138,6 +138,23 @@ Contact:	linux-iio@...r.kernel.org
>  Description:
>  		Hardware dependent values supported by the oversampling filter.
>  
> +What:		/sys/bus/iio/devices/iio:deviceX/oversampling_frequency
> +KernelVersion:	6.15
> +Contact:	linux-iio@...r.kernel.org
> +Description:
> +		Some devices have internal clocks for oversampling.
> +		Sets the resulting frequency in Hz to trigger a conversion used by
> +		the oversampling filter.
> +		If the device has a fixed internal clock or is computed based on
> +		the sampling frequency parameter, the parameter is read only.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/oversampling_frequency_available
> +KernelVersion:	6.15
> +Contact:	linux-iio@...r.kernel.org
> +Description:
> +		Hardware dependent values supported by the oversampling
> +		frequency.
> +
>  What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_raw
>  What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_supply_raw
>  What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_i_raw
> 
> ---
> base-commit: 9f36acefb2621d980734a5bb7d74e0e24e0af166
> change-id: 20250321-abi-oversampling-events-frequency-436c64fcece0
> 
> Best regards,
> -- 
> Jorge Marques <jorge.marques@...log.com>
>