3 ms·

>On other platforms you can get bootloader to hand off to kernel in subsecond timeframes, sometimes as fast as in 0.3s. Any good resources about this? I absolu

• megous 2y ago
  For 0.3s you need specialized bootloader, like eg. levinboot https://gitlab.com/DeltaGem/levinboot https://gitlab.com/DeltaGem/levinboot for Rockchip RK3399 or https://xnux.eu/p-boot/ https://xnux.eu/p-boot/ for Allwinner A64. Or make something similar for your chosen platform with U-Boot's falcon mode and making the kernel as small as possible, so that not much needs to be loaded for the initial UI (put in modules what can wait, like wifi driver, etc.). For around 1-2s you need a platform that has good SD or eMMC host implementation in U-Boot, and doesn't spend too much time initializing DRAM, or in U-Boot SPL code before MMU/CPU data cache is enabled. If the CPU is slow or not upclocked in U-Boot, not doing decompression in bootloader is also a tradeoff option that may end up being faster. Some newer Rockchip RK35xx SoCs have pretty fast boot times in this regard. (RK3399 interstingly doesn't) It's all necessarily SoC specific. On some platforms (RV1103/6) I've also experimented with using bootrom functions that normally load U-Boot to load the kernel directly, so with that approach, DTB, and kernel is being loaded right away, without re-initializing eMMC or SD card or having to load and execute a complicated DT driven bootloader like U-Boot at all. But that required quite bit of work and some reverse engineering of the Boot ROM code, so that's not just a optimization.