The Raspberry Pi Should See Much Better SPI Performance On Linux 5.4+

The SPI (Serial Peripheral Interface) pull requests to the Linux kernel normally don't get us excited, but they do when it comes with word of big performance enhancements. There are several SPI performance improvements this round but exciting us the most is the work done on the Broadcom SPI driver for Raspberry Pi hardware.

The SPI changes for Linux 5.4 come with "a big performance enhancement" for the Raspberry Pi driver to help with performance for devices connected via SPI. The patches to the driver note that when an Ethernet chip was attached to the SPI controller, there was a 30us reduction in ping time with the optimizations and a 2% reduction in CPU time.

SPI displays and other devices connected via SPI should benefit as well with faster performance. The optimization principally comes down to clearing the RX FIFO and zero-filling the TX FIFO.

More details on this work within the SPI pull request that also notes Freescale driver work improving performance and other enhancements.