Trying to boot custom kernel on Wink Hub (i.MX28)

[Rogan Dawes]

Hi folks,

I am trying to boot a custom kernel on a Wink Hub v1, which has an i.MX28
CPU, and is running U-Boot (U-Boot 2014.01-14400-gda781c6-dirty (Apr 30
2014 - 22:35:38)).

I have tried compiling my own modern kernel and putting it in place of the
vendor (Linux version 2.6.35.3-flex-dvt) kernel on the flash chip, but when
loading, I simply get the expected U-Boot loading messages, but then
nothing at all from the serial port after that.

I'm trying to figure out where my problem is most likely to be. As far as I
am aware from long-ago poking at U-Boot, the way that U-Boot passes
arguments to the kernel has changed recently? Previously it was ATAGS, and
now it expects a Device Tree Blob? Might this explain the failure to boot
that I am seeing? And yes, I understand that given that

Many thanks!

Rogan
P.S. I have also tried to boot the OpenWrt Duckbill kernel (a few years
ago), with the same results (
https://forum.openwrt.org/t/porting-openwrt-to-winkhub-v1/56966):

U-Boot 2014.01-14400-gda781c6-dirty (Apr 30 2014 - 22:35:38)

CPU:   Freescale i.MX28 rev1.2 at 454 MHz
BOOT:  NAND, 3V3
DRAM:  64 MiB
NAND:  128 MiB
In:    serial
Out:   serial
Err:   serial
Net:   FEC0 [PRIME]
Hit any key to stop autoboot:  0
=> setenv bootargs 'noinitrd console=ttyS0,115200 rootfstype=ubifs
ubi.mtd=5 root=ubi0:rootfs rw gpmi'; mtdparts default && ubi part database
&& ubifsmount ubi0:database && ubifsload ${loadaddr}
openwrt-19.07.1-mxs-uImage 1799536 && bootm ${loadaddr}
UBI: attaching mtd1 to ubi0
UBI: physical eraseblock size:   131072 bytes (128 KiB)
UBI: logical eraseblock size:    126976 bytes
UBI: smallest flash I/O unit:    2048
UBI: VID header offset:          2048 (aligned 2048)
UBI: data offset:                4096
UBI: attached mtd1 to ubi0
UBI: MTD device name:            "mtd=3"
UBI: MTD device size:            8 MiB
UBI: number of good PEBs:        64
UBI: number of bad PEBs:         0
UBI: max. allowed volumes:       128
UBI: wear-leveling threshold:    4096
UBI: number of internal volumes: 1
UBI: number of user volumes:     1
UBI: available PEBs:             6
UBI: total number of reserved PEBs: 58
UBI: number of PEBs reserved for bad PEB handling: 2
UBI: max/mean erase counter: 63/45
UBIFS: mounted UBI device 0, volume 0, name "database"
UBIFS: mounted read-only
UBIFS: file system size:   5459968 bytes (5332 KiB, 5 MiB, 43 LEBs)
UBIFS: journal size:       1015809 bytes (992 KiB, 0 MiB, 6 LEBs)
UBIFS: media format:       w4/r0 (latest is w4/r0)
UBIFS: default compressor: LZO
UBIFS: reserved for root:  269835 bytes (263 KiB)
Loading file 'openwrt-19.07.1-mxs-uImage' to addr 0x42000000 with size
1799536 (0x001b7570)...
Done
## Booting kernel from Legacy Image at 42000000 ...
   Image Name:   ARM OpenWrt Linux-4.14.167
   Created:      2020-01-29  16:05:35 UTC
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    1799472 Bytes = 1.7 MiB
   Load Address: 40008000
   Entry Point:  40008000
   Verifying Checksum ... OK
   Loading Kernel Image ... OK

Starting kernel ...