xor1010101 / rpi-linux-preempt_rt

Linux kernel patched with PREEMPT_RT for the Raspberry PI

PREEMPT_RT Linux Kernel for the Raspberry PI

This repository contains a version of the Linux kernel for the Raspberry PI2 already patched and configured with PREEMPT_RT. The only thing you have to do is to build the kernel and flash it on the microcontroller's SD card.

Current configuration

The kernel config (.config) is already set up fully-preemptible.

• bcm2709_defconfig done
• Fully Preemptible Kernel (RT)
• No old dyntics (CONFIG_NO_HZ not set)
• Default CPUFreq governor (performance)
• CAN bus subsystem support
  • Microchip MCP251x SPI CAN controllers
  • PEAK PCAN-USB/USB Pro interfaces

Build and Run

1. Clone the repository git clone --depth=1 https://github.com/dtuchsch/rpi-linux-preempt_rt.git.
2. Set up your compiler-prefix like this export CCPREFIX=/opt/rpi-tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf-
3. Open the menuconfig of the kernel configuration and adjust the settings make ARCH=arm CROSS_COMPILE=${CCPREFIX} menuconfig
4. Build the kernel make ARCH=arm CROSS_COMPILE=${CCPREFIX} zImage modules dtbs -j5
5. Flash the kernel onto the SD card and you're ready to go.

Real-Time performance

I made some rt tests with cyclictest on the same time executing hackbench to determine the worst-case latencies under high system load. My worst-case latencies were 99 microseconds with the following settings:

cyclictest -p98 -n -t
hackbench -l5000000