Raspberry Pi Pico 2 Buildroot

How to build:

git clone https://github.com/Mr-Bossman/pi-pico2-linux

cd pi-pico2-linux

git submodule update --init

# cd buildroot
# make BR2_EXTERNAL=$PWD/../ raspberrypi-pico2_defconfig
make -C buildroot BR2_EXTERNAL=$PWD/ raspberrypi-pico2_defconfig

make -C buildroot

picotool load -fu buildroot/output/images/flash-image.uf2

Designed to work with SparkFun Pro Micro - RP2350

NOTES on Atomics

On page 307 of the RP2350 Datasheet MCAUSE register CODE 7 says:

Store/AMO access fault. A store/AMO failed a PMP check, or encountered a downstream bus error. Also set if an AMO is attempted on a region that does not support atomics (on RP2350, anything but SRAM).

Atomics will only work in SRAM, the kernel is located PSRAM, not SRAM. The lr and sr atomic load and store will always return error in this region causing most code using them to behave incorrectly. Most implementations assume lr and sr will eventually succeed.

Use on other boards

This only works on the RP2350 RISC-V cores.

If you want to run this on other boards, please change the psram CS pin with the RP2350_XIP_CSI_PIN macro in package/pico2-bootloader/bootloader/src/main.c. As of now the only psram chip tested is the APS6404L and any others may not work.