It depends on the CPU. For Rockchip we have open source BL31 blob [1] and it's supported by mainline u-boot. And I think it's ring -2, because it's not a separ

It depends on the CPU. For Rockchip we have open source BL31 blob [1] and it's supported by mainline u-boot. And I think it's ring -2, because it's not a separate CPU. [1] https://www.collabora.com/news-and-blog/blog/2024/02/21/almost-a-fully-open-source-boot-chain-for-rockchips-rk3588/ https://www.collabora.com/news-and-blog/blog/2024/02/21/almo...