RP2040 basic support (draft)

[ioannisg]

Draft PR for RP2040 basic support

• SoC and SoC series definition

• Device tree support

• Board support (pico)

• Basic drivers
  - timer (SysTick)
  - serial

• Requires HAL definition

[atharvalele]

Hey! I'm interested in Zephyr and helping with the port for RPi Pico. Do you have any suggestions/tasks that I might take up?

I've gone through the documentation at https://docs.zephyrproject.org/1.12.0/porting/board_porting.html

[burumaj]

I don't think the serial driver has to be implemented. The UART peripheral is based on the ARM PL011, which is already supported by zephyr.

[burumaj]

Another thing that would need to happen is adding a stage 2 bootloader. This part would be responsible for initializing the XIP hardware. This how the pico sdk does this (https://github.com/raspberrypi/pico-sdk/tree/master/src/rp2_common/boot_stage2).
For the pico this would be using boot2_w25q080.S file. This code needs to be located at the start of the firmware image to be bootable.

Since this is a board specific property this should probably be placed in the pico board folder. Another option I can see to do this, is to configure this when selecting the SoC for example add this to KConfig.series:

if SOC_SERIES_RP20XX
choice BOOT_STAGE2_LOADER
    prompt "Support for XIP flash"

config SOC_BOOT_STAGE2_W25Q080
    bool "w25q080 stage 2"

endchoice
endif

then add configs options for all supported flash devices. Probably starting out with all devices supported by pico-sdk.
For more information on the second stage loader refer to the RP2040 datasheet chapter 2.8.1.3. Flash Second Stage.

[coderkalyan]

Hello @ioannisg , I also started this but seems you've made more progress than I have! Let me know if I can be of help

[soundsreal]

hi @ioannisg any work on the device tree support? I just bought a few chips, keen on helping out.

[gmarull]

Support has been merged now, closing