Add a section to the ad7944 documentation describing how to use the driver with SPI offloading. Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx> --- v5 changes: new patch in v5 --- Documentation/iio/ad7944.rst | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/Documentation/iio/ad7944.rst b/Documentation/iio/ad7944.rst index 0d26e56aba88..e6dbe4d7f58c 100644 --- a/Documentation/iio/ad7944.rst +++ b/Documentation/iio/ad7944.rst @@ -46,6 +46,8 @@ CS mode, 3-wire, without busy indicator To select this mode in the device tree, set the ``adi,spi-mode`` property to ``"single"`` and omit the ``cnv-gpios`` property. +This is the only wiring configuration supported when using `SPI offload support`_. + CS mode, 4-wire, without busy indicator ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -106,7 +108,6 @@ Unimplemented features ---------------------- - ``BUSY`` indication -- ``TURBO`` mode Device attributes @@ -147,6 +148,27 @@ AD7986 is a fully-differential ADC and has the following attributes: In "chain" mode, additional chips will appear as additional voltage input channels, e.g. ``in_voltage2-voltage3_raw``. +SPI offload support +=================== + +To be able to achieve the maximum sample rate, the driver can be used with the +`AXI SPI Engine`_ to provide SPI offload support. + +.. _AXI SPI Engine: http://analogdevicesinc.github.io/hdl/projects/pulsar_adc/index.html + +When SPI offload is being used, some attributes will be different. + +* ``trigger`` directory is removed. +* ``in_voltage0_sampling_frequency`` attribute is added for setting the sample + rate. +* ``in_voltage0_sampling_frequency_available`` attribute is added for querying + the max sample rate. +* ``timestamp`` channel is removed. +* Buffer data format may be different compared to when offload is not used, + e.g. the ``in_voltage0_type`` attribute. + +If the ``turbo-gpios`` property is present in the device tree, the driver will +turn on TURBO during buffered reads and turn it off otherwise. Device buffers ============== -- 2.43.0
