SPI offloading is a new feature slated to land in the 6.15 kernel. Come learn what it is and what it can be used for.

“Offloading” is a generic term that refers to using additional hardware connected to a SPI controller to handle tasks traditionally done in software, like initiating a SPI transfer and handling an interrupt when the transfer is complete. Having these functions offloaded to hardware is useful for applications like high speed data acquisition (think 1 million samples per second for an ADC) or to meet latency requirements (think CAN bus controller).

In this session, we will cover the thought process that went into designing an interface that can handle these varied applications and the solution we arrived at. We will also take a side trip to discuss hardware triggers that can be used as part of the SPI offload functionality and how they could potentially become a standalone subsystem for generic hardware triggers. Then we will take a look at how we put it all together in a real ADC driver to get 2.5 million samples per second. Finally, we will cover other potential use cases for SPI offloading and how one could go about adding support for these.