Example for tftpboot initramfs images via tty serial on the r7500v2 (i.e. for testing an initramfs image loaded to ram without having to flash an image to nand):
This example is based on the instructions provided by @quarky for the r7800 here.
Prerequisites:
- Router: R7500v2 (powered off until step 6).
- Computer running Ubuntu 18.04.2 LTS
- USB tty adapter installed following the instructions for the r7800 here. In this case, I used HiLetgo CP2102 USB 2.0 to TTL Module Serial Converter Adapter Module USB to TTL Downloader With Jumper Wires. Note that rx and tx are either reversed for on my r7500v2 (e.g. from the edge of the board its ground, tx, rx) or the connection is rx from the r7500v2 to tx on the usb tty adapter and tx from the r7500v2 to rx on the usb tty adapter. Picture below.
- Compile and install the usb to tty device drivers (in this case provided by hiletgo):
$ make
$ sudo cp cp210x.ko /lib/modules/`uname -r`/kernel/drivers/usb/serial
$ sudo insmod /lib/modules/`uname -r`/kernel/drivers/usb/serial/usbserial.ko
$ sudo insmod /lib/modules/`uname -r`/kernel/drivers/usb/serial/cp210x.ko
- Install tftp server "tftpd-hpa" and "screen" on ubuntu. If using the "ufw" firewall, allow tftp (udp port 69):
$ sudo apt update
$ sudo apt install screen tftp-hpa tftpd-hpa
$ sudo service tftpd-hpa status
$ sudo service tftpd-hpa start
$ sudo ufw allow tftp
- Copy an initramfs image to the tftpd directory. In my case, I've already built, flashed (via the r7800 TFTP method here which works perfectly on the r7500v2) and tested an openwrt "factory" image on the router; however, it is likely not necessary to have an openwrt image already flashed to nand to tftpboot an initramfs from ram. I used the initramfs automatically generated during the build of a known working image to make sure the initramfs image will work.
$ sudo cp ~/openwrt/bin/targets/ipq806x/generic/openwrt-ipq806x-netgear_r7500v2-initramfs-uImage /var/lib/tftpboot/
- Connect the computer ethernet port to a LAN port on the router, set up and enable the computer ethernet as static ipv4 address/netmask: 192.168.1.10/24, gateway: 192.168.1.1. Connect the usb tty serial device to the router and computer (a usb extension cable to the usb tty adapter works for me).
- Start a screen session. I use:
sudo screen -h 1000 -L -Logfile ~/r7500v2-`date +"%Y%m%d-%H%M"`.log /dev/ttyUSB0 115200
- Power on the router.
- At this point you should see the router booting up in screen session started above. If not, you'll need to trouble shoot the usb tty serial setup - it took me a few tries... When you see something similar too:
U-Boot 2012.07 [local,local] (May 29 2015 - 19:03:53)
U-boot 2012.07 dni1 V1.5 for DNI HW ID: 29764958 NOR flash 0MB NAND flash 128MB RAM 512MB 1st Radio 3x3 2nd Radio 4x4
smem ram ptable found: ver: 0 len: 5
DRAM: 491 MiB
NAND: SF: Unsupported manufacturer 00
ipq_spi: SPI Flash not found (bus/cs/speed/mode) = (0/0/48000000/0)
128 MiB
MMC:
*** Warning - bad CRC, using default environment
PCI0 Link Intialized
PCI1 Link Intialized
In: serial
Out: serial
Err: serial
131072 bytes read: OK
cdp: get part failed for 0:HLOS
Net: MAC1 addr:XX:XX:XX:XX:XX:XX
athrs17_reg_init: complete
athrs17_vlan_config ...done
S17c init done
MAC2 addr:XX:XX:XX:XX:XX:XX
eth0, eth1
Hit any key to stop autoboot: 1
(IPQ) #
Interrupt U-Boot by pressing any key (in the serial console) when prompted. You have only 2-3 seconds before U-Boot proceeds to boot from the NAND flash.
- Find the ram load address to use with the uboot "tftpboot" command from the uboot command "printenv":
(IPQ) # printenv
baudrate=115200
bootargs=console=ttyHSL1,115200n8
bootcmd=sleep 2; nmrp; if loadn_dniimg 0 0x1480000 0x44000000 && chk_dniimg 0x44000000; then bootipq2; else fw_recovery; fi
bootdelay=2
config_ubi_prepare=mtdparts default; ubi part dnidata
ethact=eth0
ipaddr=192.168.1.1
language_ubi_prepare=mtdparts default; ubi part language
loadaddr=0x42000000
machid=1260
modelid=R7500v2
serverip=192.168.1.10
stderr=serial
stdin=serial
stdout=serial
updateloader=ipq_nand sbl && nand erase 0x00c80000 0x00580000 && imgaddr=0x42000000 && source $imgaddr:script
Environment size: 585/262140 bytes
In my case, the ram load address is "44000000" and is shown in the "bootcmd" environment variable as 0x44000000. Using the loadaddr environment variable "0x42000000" did not work (I think this is the nand address to load an image from).
- test that you can see the tftp server from uboot:
(IPQ) # ping 192.168.1.10
Using eth1 device
host 192.168.1.10 is alive
- Load the initramfs image via "tftpboot":
(IPQ) # tftpboot 44000000 192.168.1.10:openwrt-ipq806x-netgear_r7500v2-initramfs-uImage
Using eth1 device
TFTP from server 192.168.1.10; our IP address is 192.168.1.1
Filename 'openwrt-ipq806x-netgear_r7500v2-initramfs-uImage'.
Load address: 0x44000000
Loading: #################################################################
#################################################################
#################################################################
#################################################################
#################################################################
###############################################################
done
Bytes transferred = 5683228 (56b81c hex)
- boot the image:
(IPQ) # bootm
Image Name: ARM OpenWrt Linux-4.19.57
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 5683164 Bytes = 5.4 MiB
Load Address: 42208000
Entry Point: 42208000
Verifying Checksum ... OK
Loading Kernel Image ... OK
OK
mtdparts variable not set, see 'help mtdparts'
no partitions defined
defaults:
mtdids : nand0=msm_nand
mtdparts: mtdparts=msm_nand:3584K@0x7980000(language),3M@0x7d00000(dnidata)
info: "mtdparts" not set
Using machid 0x1260 from environment
Starting kernel ...
[ 0.000000] Booting Linux on physical CPU 0x0
[ 0.000000] Linux version 4.19.57 (n@E6410) (gcc version 7.4.0 (OpenWrt GCC 7.4.0 r10459+4-1174b94bc9)) #0 SMP Tue Jul 9 23:20:21 2019
[ 0.000000] CPU: ARMv7 Processor [512f04d0] revision 0 (ARMv7), cr=10c5787d
...
When the kernel log messages stop, hit any key to get a console and go from there. Note, I could not see my "overlay" files from my previous nand flashed openwrt image; however, typing "reboot" from the serial console and not interupting uboot as described above got me back to my nand flashed environment. Nice.
