Received-SPF: pass (google.com: domain of linux-kernel+bounces-158664-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
From: David Lechner <dlechner@baylibre.com>
To: Jonathan Cameron <jic23@kernel.org>
Cc: David Lechner <dlechner@baylibre.com>,
	Michael Hennerich <Michael.Hennerich@analog.com>,
	=?utf-8?q?Nuno_S=C3=A1?= <nuno.sa@analog.com>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-iio@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org
Subject: [PATCH 2/2] docs: iio: ad7944: add documentation for chain mode
Date: Thu, 25 Apr 2024 09:10:00 -0500
Message-ID: <20240425-iio-ad7944-chain-mode-v1-2-9d9220ff21e1@baylibre.com>
In-Reply-To: <20240425-iio-ad7944-chain-mode-v1-0-9d9220ff21e1@baylibre.com>
References: <20240425-iio-ad7944-chain-mode-v1-0-9d9220ff21e1@baylibre.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 8bit

Add documentation for chain mode support that was recently added to the
AD7944 ADC driver.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 Documentation/iio/ad7944.rst | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/Documentation/iio/ad7944.rst b/Documentation/iio/ad7944.rst
index f418ab1288ae..0d26e56aba88 100644
--- a/Documentation/iio/ad7944.rst
+++ b/Documentation/iio/ad7944.rst
@@ -24,7 +24,7 @@ Supported features
 SPI wiring modes
 ----------------
 
-The driver currently supports two of the many possible SPI wiring configurations.
+The driver currently supports three of the many possible SPI wiring configurations.
 
 CS mode, 3-wire, without busy indicator
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -68,6 +68,27 @@ CS mode, 4-wire, without busy indicator
 To select this mode in the device tree, omit the ``adi,spi-mode`` property and
 provide the ``cnv-gpios`` property.
 
+Chain mode, without busy indicator
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. code-block::
+
+                                                                 +-------------+
+                  +-------------------------+--------------------| CS          |
+                  v                         v                    |             |
+        +--------------------+    +--------------------+         |     HOST    |
+        |        CNV         |    |        CNV         |         |             |
+   +--->| SDI   AD7944   SDO |--->| SDI   AD7944   SDO |-------->| SDI         |
+   |    |        SCK         |    |        SCK         |         |             |
+  GND   +--------------------+    +--------------------+         |             |
+                  ^                         ^                    |             |
+                  +-------------------------+--------------------| SCLK        |
+                                                                 +-------------+
+
+To select this mode in the device tree, set the ``adi,spi-mode`` property to
+``"chain"``, add the ``spi-cs-high`` flag, add the ``#daisy-chained-devices``
+property, and omit the ``cnv-gpios`` property.
+
 Reference voltage
 -----------------
 
@@ -86,7 +107,6 @@ Unimplemented features
 
 - ``BUSY`` indication
 - ``TURBO`` mode
-- Daisy chain mode
 
 
 Device attributes
@@ -108,6 +128,9 @@ AD7944 and AD7985 are pseudo-differential ADCs and have the following attributes
 | ``in_voltage0_scale``                 | Scale factor to convert raw value to mV.                     |
 +---------------------------------------+--------------------------------------------------------------+
 
+In "chain" mode, additional chips will appear as additional voltage input
+channels, e.g. ``in_voltage1_raw``.
+
 Fully-differential ADCs
 -----------------------
 
@@ -121,6 +144,9 @@ AD7986 is a fully-differential ADC and has the following attributes:
 | ``in_voltage0-voltage1_scale``        | Scale factor to convert raw value to mV.                     |
 +---------------------------------------+--------------------------------------------------------------+
 
+In "chain" mode, additional chips will appear as additional voltage input
+channels, e.g. ``in_voltage2-voltage3_raw``.
+
 
 Device buffers
 ==============

-- 
2.43.2