linux-kernel - Re: [PATCH v5 7/7] docs: iio: Add documentation for AD4000

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Date: Wed, 26 Jun 2024 10:43:17 -0500
From: David Lechner <dlechner@...libre.com>
To: Marcelo Schmitt <marcelo.schmitt@...log.com>, broonie@...nel.org,
 lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org,
 robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 nuno.sa@...log.com, corbet@....net, marcelo.schmitt1@...il.com
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-spi@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 7/7] docs: iio: Add documentation for AD4000

On 6/25/24 4:55 PM, Marcelo Schmitt wrote:
> Document wiring configurations for the AD4000 series of ADCs.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> ---
>  Documentation/iio/ad4000.rst | 131 +++++++++++++++++++++++++++++++++++
>  Documentation/iio/index.rst  |   1 +
>  MAINTAINERS                  |   1 +
>  3 files changed, 133 insertions(+)
>  create mode 100644 Documentation/iio/ad4000.rst
> 
> diff --git a/Documentation/iio/ad4000.rst b/Documentation/iio/ad4000.rst
> new file mode 100644
> index 000000000000..de8fd3ae6e62
> --- /dev/null
> +++ b/Documentation/iio/ad4000.rst
> @@ -0,0 +1,131 @@
> +.. SPDX-License-Identifier: GPL-2.0-only
> +
> +=============
> +AD4000 driver
> +=============
> +
> +Device driver for Analog Devices Inc. AD4000 series of ADCs.
> +
> +Supported devices
> +=================
> +
> +* `AD4000 <https://www.analog.com/AD4000>`_
> +* `AD4001 <https://www.analog.com/AD4001>`_
> +* `AD4002 <https://www.analog.com/AD4002>`_
> +* `AD4003 <https://www.analog.com/AD4003>`_
> +* `AD4004 <https://www.analog.com/AD4004>`_
> +* `AD4005 <https://www.analog.com/AD4005>`_
> +* `AD4006 <https://www.analog.com/AD4006>`_
> +* `AD4007 <https://www.analog.com/AD4007>`_
> +* `AD4008 <https://www.analog.com/AD4008>`_
> +* `AD4010 <https://www.analog.com/AD4010>`_
> +* `AD4011 <https://www.analog.com/AD4011>`_
> +* `AD4020 <https://www.analog.com/AD4020>`_
> +* `AD4021 <https://www.analog.com/AD4021>`_
> +* `AD4022 <https://www.analog.com/AD4022>`_
> +* `ADAQ4001 <https://www.analog.com/ADAQ4001>`_
> +* `ADAQ4003 <https://www.analog.com/ADAQ4003>`_
> +
> +Wiring connections
> +------------------
> +
> +Devices of the AD4000 series can be connected to the SPI host controller in a
> +few different modes.
> +
> +CS mode, 3-wire turbo mode
> +^^^^^^^^^^^^^^^^^^^^^^^^^^

The datasheet also has the same diagram in _Figure 55. CS Mode, 4-Wire Turbo Mode
Connection Diagram_. So maybe we should call this "register support mode" or
something like that instead of mentioning 3 or 4-wire?

> +
> +Datasheet "3-wire" mode is what most resembles standard SPI connection which,
> +for these devices, comprises of connecting the controller CS line to device CNV
> +pin and other SPI lines as usual. This configuration is (misleadingly) called
> +"CS Mode, 3-Wire Turbo Mode" connection in datasheets.
> +NOTE: The datasheet definition of 3-wire mode for the AD4000 series is NOT the
> +same of standard spi-3wire mode.
> +This is the only connection mode that allows configuration register access but
> +it requires the SPI controller to support the ``SPI_MOSI_IDLE_HIGH`` feature.
> +
> +Omit the ``adi,sdi-pin`` property in device tree to select this mode.
> +
> +::
> +
> +                                         +-------------+
> +     + ----------------------------------| SDO         |
> +     |                                   |             |
> +     |               +-------------------| CS          |
> +     |               v                   |             |
> +     |    +--------------------+         |     HOST    |
> +     |    |        CNV         |         |             |
> +     +--->| SDI   AD4000   SDO |-------->| SDI         |
> +          |        SCK         |         |             |
> +          +--------------------+         |             |
> +                    ^                    |             |
> +                    +--------------------| SCLK        |
> +                                         +-------------+
> +

I think the rest of the explanations are good.