Thank you very much for the very detailed information :) I also found some very useful information.
https://software-dl.ti.com/processor-sdk-linux/esd/docs/latest/linux/Foundational_Components_U-Boot.html RobertCNelson schrieb am Mittwoch, 18. November 2020 um 17:31:42 UTC+1: > On Wed, Nov 18, 2020 at 10:20 AM Georg Gast <schors...@gmail.com> wrote: > > > > Hello Robert, > > thanks for the answer. So may i sumarize how the BBAI boots: > > > > The Am5729 on the BBAI boots like: > > - Reset Vector in the Arm start from an internal firmware. > > - The internal firmware knows how to read some sectors from SD/MMC > > - The internal firmware loads the MLO/SPL from the SD/MMC > > sudo dd if=./u-boot/MLO of=${DISK} count=2 seek=1 bs=128k > > > - The MLO loads u-boot.img also from some sectors on the SD/MMC > > These are correct, the "sector" is documented and the same as am335x, > am57xx also supports reading the files from FAT file system. > > sudo dd if=./u-boot/u-boot.img of=${DISK} count=4 seek=1 bs=384k > > > - u-boot.img loads uEnv.txt also from some sectors > > For BeagleBoard.org, u-boot.img looks for /boot/extlinux/extlinux.conf > and then "uEnv.txt" in multiple locations on FAT, EXTx, and BTRFS.. > > For mainline u-boot, u-boot.img looks for /boot/extlinux/extlinux.conf > then /boot/uEnv.txt in multiple locations on fat/extX... (BTRFS not > built by default) > > > - u-boot loads kernel/fdt and initrd from the target partitions boot > folder > > For BeagleBoard.org, uEnv.txt set's the variables that load specific > kernel/initrd/dtb. > > For Mainline, either it uses the generic extlinux.conf vales, or just > loads /boot/uImage...(aka defaults..) > > > - Linux starts. > > > > Is this correct? > > > > About the pinmux stuff nuked from mainline: > > Does it mean, the kernel passed FDT from u-boot can be parsed from the > kernel but any pinmuxing (say: set pins to i2c) can't be done from the > kernel? Or is this FDT parsed from u-boot and pinmux set? As far as i know: > u-boot has basic hardware knowledge in it [3][4]. Can only at this stage > the pinmux be changed? > > For "AM57xx", u-boot.img "Must" set the pinmux , while we update it in > teh device-tree, it's not teh 100% approved way.. > > > On early versions of the BBB, the SD card had a partition 1 (W95 FAT32) > and FS FAT16 and bootflag set. This partition contained MLO and u-boot.img. > Like modern PC systems with their EFI partition. I still have images from > 2014 with Angstrom linux which have this setup. > > And 90% of the customer issues we faced at BeagleBoard.org, was > customers who "formatted" the FAT32 partition to get more space, and > then angrily returned it to the retailer as defective.. > > > Why did u-boot/TI/whoever switch back to bootloaders in sectors like it > was before EFI hit the PC system? Is this something that is different from > SOC to SOC? > > THUS, I nuked the split fat/ext4 partition as a support nightmary.. > > Customer failure returns dropped, I consider the sector method a > success for end user reliability of these specific SBC's.... > > Regards, > > -- > Robert Nelson > https://rcn-ee.com/ > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/deb45714-665e-4141-9e71-2cfbe5540e28n%40googlegroups.com.
