To boot OpenWrt on P2812HNU-Fx the stock u-boot has to be exchanged by a custom one. @ScApi has provided these some 6 years ago. It has been in my boxes since then. However, when trying to boot an initramfs-kernel.bin, it has since long failed with 'Uncompressing Kernel Image ... LZMA: uncompress or overwrite error 7 - must RESET b', followed by a reboot. Somewhere, I don't remember where, I've read that this u-boot can't uncompress more than 8MiB target space. I can imagine an initramfs-kernel is bigger. For the F3 ScApi provided a TFTP boot image size fix, which might deal with that, but unfortunately not for the F1.
Problem is now that when sysupgrading to snapshot, I get the same lzma error on boot of the box. Binwalk told me that the uncompressed kernel is 8550713 bytes, while the uncompressed kernel of 21.01-rc3 is 7883213 bytes. so indeed the 8MiB limit has been exceeded. Either a new u-boot is needed, or the decompressor has to be piggybacked on the kernel in order to boot this.
OpenWrt/Lede never provided a nand u-boot for any xrx200 device, but it provides a ram version for the P2812HNU-Fx and others, and a nor version for some others. Is there something special in nand u-boot making it harder to provide this? How should I start to build a new nand u-boot?
In short words, yes.
For nand lantiq loads only first bytes (spl boot) witch then loads rest of uboot, as it was long ago I dont remember what was the fix for F3 but they share most od the code. I dont have any of this devices now so I can only help to trobleshoot.
OK, thanks. I downloaded the OpenWrt sources, and found in packages/boot/u-boot-lantiq/Makefile
define U-Boot/p2812hnufx_ram
NAME:=ZyXEL P-2812HNU-Fx (RAM)
BUILD_SUBTARGET:=xrx200
BUILD_DEVICES:=zyxel_p-2812hnu-f1
DDR_SETTINGS:=board/zyxel/p2812hnufx/ddr_settings.h
endef
define U-Boot/p2812hnufx_nandspl
NAME:=ZyXEL P-2812HNU-Fx (NAND SPL)
BUILD_SUBTARGET:=xrx200
BUILD_DEVICES:=zyxel_p-2812hnu-f1
UBOOT_IMAGE:=u-boot.ltq.lzo.nandspl
DEPENDS+=@BROKEN
endef
So there is a nand u-boot somehow, but it's marked broken. I removed the 'broken' flag, and it built without any problems. But the binary is not just a binary u-boot with a pre-loader in front:
$ binwalk u-boot.ltq.lzo.nandspl
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
8320 0x2080 CRC32 polynomial table, little endian
9412 0x24C4 LZO compressed data
16448 0x4040 LZO compressed data
124700 0x1E71C LZO compressed data
So I suppose the first 8320 bytes contain both a preloader, and a decompressor. Some extra level in complexity. I suppose there is no way testing this without flashing? Any idea why it's marked broken?
It's a bit strange that the source tree does contain a nand u-boot for the F1, but not a nor for the F3, while it provides nor u-boot's for other Lantiqs.
I found this commit from 2017 to be responsible for the 'broken' mark. On my system is lzop available, and so it build. Unfortunately the comment doesn't mention where NAND-SPL support is broken, but assuming it's in u-boot itself, odds are that it's repaired by now. I'll just try to flash it.
Scratch that. U-boot 2013.10 is used, so if the 'solution' is not in the OpenWrt patches, it's not repaired.
Indeed NAND-SPL is broken. After flashing the u-boot I got no further than
ROM VER: 1.0.5
CFG 06
NAND
NAND Read OK
@Mafketel , when googling I found you were also experiencing this problem. Did you ever solve it?
On my github You can find U-Boot with commit regarding Livebox, or one for HHv5 with commits from @xdarklight, use Them as base, as far as I can tell they have this problem mostly fixed.
Solved. When sifting the trunk files I found the 16MiB patch is in package/boot/uboot-lantiq/patches/0107-MIPS-add-board-support-for-ZyXEL-P-2812HNU-Fx.patch :
+
+#define CONFIG_SYS_BOOTM_LEN 0x1000000 /* 16 MB */
+
With the patch reverted, I build the nand-spl u-boot a second time, extracted the lzo compressed part using binwalk, and looked at the differences in the binaries. It appeared there were only four bytes different (apart from a timestamp in ascii), two pairs '00 80' which had become '01 00'. (I think I know how the 32MiB patch would work out 
). So I took @ScApi's r47026 bootloader, extracted the payload, hexedited the file and repackaged it. (And when I was there, I also edited the timestamp). It worked! This bootloaded can uncompress to >8MiB:
ROM VER: 1.0.5
CFG 06
NAND
NAND Read OK
U-Boot SPL 2013.10-openwrt5 (Nov 18 2014 - 19:54:01)
SPL: initializing NAND flash
SPL: checking U-Boot image
SPL: loading U-Boot to RAM
SPL: decompressing U-Boot with LZO
SPL: jumping to U-Boot
U-Boot 2013.10-openwrt5 (Jul 06 2021 - 10:04:01) P-2812HNU-Fx
Board: ZyXEL P-2812HNU-Fx
SoC: Lantiq VRX288 v1.1
CPU: 500 MHz
IO: 250 MHz
BUS: 250 MHz
BOOT: NAND
DRAM: 128 MiB
NAND: 128 MiB
In: serial
Out: serial
Err: serial
Net: ltq-eth
Hit any key to stop autoboot: 2 0
P-2812HNU-Fx # tftpboot openwrt-19.07.7-lantiq-xrx200-zyxel_p-2812hnu-f1-initramfs-kernel.bin
ltq_phy: addr 0, link 1, speed 1000, duplex 1
ltq_phy: addr 1, link 0, speed 10, duplex 0
ltq_phy: addr 17, link 0, speed 10, duplex 0
ltq_phy: addr 19, link 0, speed 10, duplex 0
ltq_phy: addr 5, link 0, speed 10, duplex 0
Using ltq-eth device
TFTP from server 192.168.1.2; our IP address is 192.168.1.1
Filename 'openwrt-19.07.7-lantiq-xrx200-zyxel_p-2812hnu-f1-initramfs-kernel.bin'.
Load address: 0x82000000
Loading: *#################################################################
#################################################################
#################################################################
#################################################################
#####################################################
8 MiB/s
done
Bytes transferred = 4586129 (45fa91 hex)
P-2812HNU-Fx # bootm
## Booting kernel from Legacy Image at 82000000 ...
Image Name: MIPS OpenWrt Linux-4.14.221
Created: 2021-02-15 15:22:37 UTC
Image Type: MIPS Linux Kernel Image (lzma compressed)
Data Size: 4586065 Bytes = 4.4 MiB
Load Address: 80002000
Entry Point: 80002000
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Starting kernel ...
[ 0.000000] Linux version 4.14.221 (builder@buildhost) (gcc version 7.5.0 (OpenWrt GCC 7.5.0 r11306-c4a6851c72)) #0 SMP Mon Feb 15 15:22:37 2021
I uploaded the u-boot here. Thanks again, @ScApi , for providing the original u-boot!
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