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 - The MLO loads u-boot.img also from some sectors on the SD/MMC - u-boot.img loads uEnv.txt also from some sectors - u-boot loads kernel/fdt and initrd from the target partitions boot folder - 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? 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. 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? Best Regards Georg [1] https://www.kernel.org/doc/html/v5.4/driver-api/pinctl.html [2] https://gitlab.denx.de/u-boot/u-boot/-/tree/master/board/ti/am335x [3] https://gitlab.denx.de/u-boot/u-boot/-/blob/master/board/ti/am57xx/board.c#L834 [4] https://gitlab.denx.de/u-boot/u-boot/-/blob/master/board/ti/am57xx/board.c#L860 RobertCNelson schrieb am Dienstag, 17. November 2020 um 23:48:38 UTC+1: > On Tue, Nov 17, 2020 at 4:29 PM Georg Gast <schors...@gmail.com> wrote: > > > > Hi everyone, > > i have an old Beaglebone Black (short after it was released) and now i > got a new BBAI. The BBB i could run with a mainline kernel and mainline > u-boot and a stock Debian/armhf. > > > > I build u-boot from source and rest was qemu-debootstraped. > > > > For other SBC's like the Pi4 there is a description how exactly the > bootprocess works. Also the BBB got a description how to setup the SD card > to boot it. > > > > My first try was to setup the SD card as i did with the BBB but it > didn't work out. When i flash the Flasher Image i can restore my MMC and it > works again. Even if i copy the content of the original MMC to the SD card > it works. > > > > I got a TTL UART adapter and i can see u-boot and work with it on the > stock images. My interest is in understanding the boot sequences of these > SBCs and run them most of the time with Debian and upstream sources. > > > > Could you point me to a description of the boot sequence? The offical > system manual is still on TODO in these areas. > > For pure mainline/debian, just setup extlinux.. U-Boot will load that > file and do the generic bootup, just make sure to disable quiet > > /boot/extlinux/extlinux.conf > > TI nuked all am57xx pinmuxing in the mainline kernel, so all pinmux > values need to be setup in u-boot, i'm not sure if that's 100% yet.. > (aka i don't think eMMC was working) > > > 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/b41a1a40-81cc-47c0-8323-0ea217d3873en%40googlegroups.com.
