I am trying to setup a system in the RBP 3B+ using UBoot as bootloader. I am trying to get it to boot the fastest I can (at the moment, I have a Class 10 SD card) and I am getting around 1.4s from power in the 3V3 rail to UART initialization (I am seeing the UART going from GND to 3V3 which should be the default floating value). I have Uboot DEBUG output enable to see the first characters in the UART as soon as it starts doing things (UBoot); I am getting it printing at around 1.8s (since power up).
I am wondering if there is any chance to improve the time from power up to uboot execution? I am wondering if some config.txt options could help? (I tried with bootcode_delay=0, boot_delay=0, boot_delay_ms=0 without much improvement). Any combinantions of fixup_cd.dat/fixup_x.dat or start_cd.elf/start_x.elf could speed it up? It looked like removing the DTB from the boot partition helped (saving some time). Could the boot sequence taking longer than normal due to my FAT partition table (see below, 11 different partitions)?
I am not sure if I am hitting a wall getting Uboot booting in 1.8s or it can be done faster. Thank you for your help :D
Some context information: - Class 10 SD Card - No USB devices connected. - Ethernet pluged-in. - HDMI Screen connected. - Powering using the standard RBP power supply. - Around 11 partitions in the SD Card (all of them ext4 but the boot one which is FAT32 LBA with bootflag enabled).