I have my MiWIFI r3d router not booting. I flashed another kernel to kernel1 partition - it starts but then cannot find root fs partition for some reasons and reboots. Standard Xiaomi recovery procedure with FAT formatted USB stick doesn't work. Maybe, it is because the device reboots in 3 seconds while the recovery mode is expected to be activated in 5 seconds. I'm trying to restore my device via U-Boot console, however I cannot find bootmenu typical for other MiWIFI devices. So I cannot enter U-Boot console or activate TFTP mode. Here is my U-Boot log got via serial connection:

U-Boot 2012.07 [ ,unknown] (May 24 2018 - 09:44:47)

smem ram ptable found: ver: 0 len: 5
DRAM:  494 MiB
NAND:  SF: Unsupported manufacturer 00
ipq_spi: SPI Flash not found (bus/cs/speed/mode) = (0/0/48000000/0)
256 MiB
PCI0 Link Intialized
PCI1 Link Intialized
In:    serial
Out:   serial
Err:   serial
cdp: get part failed for 0:HLOS
cdp: get part failed for rootfs
Net:   MAC1 addr:40:31:3c:d8:b1:1a
athrs17_reg_init: complete
athrs17_vlan_config ...done
S17c init  done
MAC2 addr:40:31:3c:d8:b1:1b
eth0, eth1

NAND read: device 0 offset 0xc00000, size 0x400000
4194304 bytes read: OK
   Image Name:   ARM OpenWrt Linux-4.14.131
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    2185323 Bytes = 2.1 MiB
   Load Address: 42208000
   Entry Point:  42208000
   Verifying Checksum ... OK
   Loading Kernel Image ... OK
OK

device nand0 nand, # parts = 9
#: name                size                offset                mask_flags
0: Bdata               0x00080000        0x00600000        0
1: crash               0x00080000        0x00680000        0
2: crash_syslog        0x00080000        0x00700000        0
3: rsvd                0x00080000        0x00780000        0
4: kernel0             0x00400000        0x00800000        0
5: kernel1             0x00400000        0x00c00000        0
6: rootfs0             0x02800000        0x01000000        0
7: rootfs1             0x02800000        0x03800000        0
8: overlay             0x0a000000        0x06000000        0

active partition: nand0,0 - (Bdata) 0x00080000 @ 0x00600000

defaults:
mtdids  : none
mtdparts: none
Setting up atags for msm partition: Bdata
Setting up atags for msm partition: crash
Setting up atags for msm partition: crash_syslog
Setting up atags for msm partition: rsvd
Setting up atags for msm partition: kernel0
Setting up atags for msm partition: kernel1
Setting up atags for msm partition: rootfs0
Setting up atags for msm partition: rootfs1
Setting up atags for msm partition: overlay
Using machid 0x1260 from environment

Starting kernel ...

Is there any way to enter U-Boot console or TFTP mode on MiWIFI r3d router via serial connection?