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

[Jonathan Cameron]

On Tue, 8 Apr 2025 10:20:29 +0200
Jorge Marques <jorge.marques@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> 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.

This patch looks fine but we will only merge it with first user so
please add it to that series.

Jonathan

> ---
> 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@xxxxxxxxxx
> ---
>  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@xxxxxxxxxxxxxxx
>  Description:
>  		Hardware dependent values supported by the oversampling filter.
>  
> +What:		/sys/bus/iio/devices/iio:deviceX/oversampling_frequency
> +KernelVersion:	6.15
> +Contact:	linux-iio@xxxxxxxxxxxxxxx
> +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@xxxxxxxxxxxxxxx
> +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,