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Merge series from David Lechner <dlechner@baylibre.com>: As a recap, here is the background and end goal of this series: The AXI SPI Engine is a SPI controller that has the ability to record a series of SPI transactions and then play them back using a hardware trigger. This allows operations to be performed, repeating many times, without any CPU intervention. This is needed for achieving high data rates (millions of samples per second) from ADCs and DACs that are connected via a SPI bus. The offload hardware interface consists of a trigger input and a data output for the RX data. These are connected to other hardware external to the SPI controller. To record one or more transactions, commands and TX data are written to memories in the controller (RX buffer is not used since RX data gets streamed to an external sink). This sequence of transactions can then be played back when the trigger input is asserted. This series includes core SPI support along with the first SPI controller (AXI SPI Engine) and SPI peripheral (AD7944 ADC) that use them. This enables capturing analog data at 2 million samples per second. The hardware setup looks like this: +-------------------------------+ +------------------+ | | | | | SOC/FPGA | | AD7944 ADC | | +---------------------+ | | | | | AXI SPI Engine | | | | | | SPI Bus ============ SPI Bus | | | | | | | | | +---------------+ | | | | | | | Offload 0 | | | +------------------+ | | | RX DATA OUT > > > > | | | | TRIGGER IN < < < v | | | +---------------+ | ^ v | | +---------------------+ ^ v | | | AXI PWM | ^ v | | | CH0 > ^ v | | +---------------------+ v | | | AXI DMA | v | | | CH0 < < < | | +---------------------+ | | | +-------------------------------+
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.