A Playground for Firmware development for RTL8372/RTL8373 based 2.5GBit Switches.
For each hardware configuration of these devices, there is usually a managed and an umanaged version sold, with mostly identical hardware. The aim is to provide management features also for unmanaged devices with additional features such as Management VLAN, dhcp servers, multi-language support, IPv6 and TLS-encrypted web-pages.
The playground currently provides a minimal alternative firmware for both the managed and unmanaged switches. When used with unmanaged switches, it will provide some management features such as setting up VLANs, mirroring ports and provide a Web-Server (currently no functions, really), but will need to be configured via a serial connection. Installation on managed devices only makes sense for developers, as plenty of features of the managed switches are not supported, yet.
At this point, the firmware can be installed on the hardware as given below, all of the ports and SFP-slots will be supported. The following has been tested: On the keepLINK kp-9000-6hx-x (RTL8372 + RTL8221B 2.5GBit PHY: 5 x 2.5GBit + 1x 10GBit SFP+), at present the system will provide the same featurs as a dumb switch plus a tiny TCP stack that will allow to reply to ARP and ping messages, thus enabling pinging the device. VLAN and mirroring can be configured (but not saved to flash). The ports served by the RTL8372 will be 100M/1G/2.5G auto-detect. Port 5 to RTL8221B PHY SerDes configuration works and supports 1GBit and 2.5GBit Ethernet (SGMII/HISGMII). SFP module insert/removal identification and reading of the SFP EEProm works. SFP module configuration works, too, tested for 1G, 2.5G and 10G Ethernet and Fiber modules.
The 4-Port Ethernet + 2 Port SFP+ devices (e.g. KP-9000-6HX-x2) are fully supported, too (e.g. KP-9000-6hx-x2) with the same features as above. In particular all fiber/Ethernet modules work in both SFP+ ports.
On the 9-port devices with RTL8273 + RTL8224 (for example kp-9000-9xh-x) all ports will work for switching and CPU-access, the SFP+ port will work normally and TCP connectivity will work as above. Not all features of the RTL8224-ports (the first 4) have been tested.
To do meaningful development you will need to use a serial console, so soldering skills are required. Flashing must be done via a SOIC-8 PatchClamp or by soldering a socket for the flash chip.
UPDATE: The Code comes with a port of the uIP TCP/IP stack and includes a minimal web-server that can be used to work with the switch, so if you use a patch-clamp for updating the firmware (~3 USD/EUR), you can try this out without the need to solder anything. See the instructions below. Note that updating the firmware of a managed switch with the images created in this project via the OEM web-interface will not work, because it is currently unknown how to generate the require checksum, see this issue. However, if you use the patch-clamp to flash, this is not a problem.
If you don't want to open your device, you can use the project's code to learn about the devices by looking at the image using e.g. Ghidra.
Install the following particular build requisites (Debian 12, should work on Ubuntu)
sudo apt install sdcc xxd python
Now, building the firmware image should work:
$ make
sdas8051 -plosgff crtstart.asm
sdcc -mmcs51 -c rtlplayground.c
sdcc -mmcs51 -c rtl837x_flash.c
sdcc -mmcs51 -Wl-bHOME=0x100 -o rtlplayground.ihx crtstart.rel rtlplayground.rel rtl837x_flash.rel
objcopy --input-target=ihex -O binary rtlplayground.ihx rtlplayground.img
if [ -e rtlplayground.bin ]; then rm rtlplayground.bin; fi
echo "0000000: 00 40" | xxd -r - rtlplayground.bin
cat rtlplayground.img >> rtlplayground.bin
Note, that the image generated ends in .bin, not .img, in order to make IMSProg happy.
You can play with the image using ghidra or flash real Switch Hardware
If you do not have an RTL837x-based switch device such as the ones mentionned here: [Up-N-Atoms 2.5 GBit RTL Switch hacking guide] (https://github.com/up-n-atom/SWTG118AS) or one of the other that deployment was tested on, including:
- keepLINK kp-9000-6hx-x2 (RTL8372: 4x 2.5GBit + 2x 10GBit SFP+)
- keepLINK KP-9000-6XHML-X2, same as above, but Managed
- keepLINK kp-9000-6hx-x (RTL8372 + RTL8221B 2.5GBit PHY: 5 x 2.5GBit + 1x 10GBit SFP+)
- keepLINK kp-9000-9xh-x-eu (1 x RTL8373 + RTL8224: 8x 2.5GBit + 1x 10GBit SFP+)
- Lianguo LG-SWTGW218AS (RTL8373 + RTL8224 PHY: 8x 2.5GBit + 1x 10GBit SFP+)
- No-Name ZX-SWTGW215AS, managed version of kp-9000-6hx-x, ordered on AliExpress as keepLINK 5+1 port managed
Start ghidra, load file starting from offset 0x0002 into memory starting at 0x0000. The lengthe is 0x10000. Select generic 8051, big endian.
After loading, the boot vector is at 0x0000, which will jump to 0x0100 for the boot routine.
The firmware uses only bank 1 of the RTL837x since it is quite short. Otherwise the firmware would be organized as follows
--------------------------- 0x0000 ---------------------------------
Boot-Vector
ISRs
Common Code
Trampoline for inter-bank calls
Inter-bank calls, calling trampoline, one for each callable function
----- Bank 1 0x4000 ------ ---- Bank 2 0x4000 ----- -------- .....
Overlay 1 Overlay 2 Overlay n
--------- 0xffff --------- -------- 0xffff -------- -------- 0xffff
The RTL837x firmware images are organized as follows: The first 2 bytes of the image give the size of the prefetched data at the start of the CPU power up. The default is 0x4000 (bytes: 0x00 0x40), which means that the entire shared area of the code memory in all banks, 0x4000 bytes is read immediately into the code RAM.
Common code starts at 0x0002 in the image and has length 0x3ffd, the first bank starts at 0x4000 in the image, is mapped to 0x4000 and has length 0xc000. The second bank starts at 0x10000, is mapped to 0x4000 and has length 0xc000. The third bank would start at 0x1c000 and would again be mapped to 0x4000. There are about 30 banks in use for managed switches, unmanaged ones use 2-3, while the hardware would allow to use 0x3f banks, i.e. up to 4 MB of flash.
The current image uses Common BANK0 and the first BANK1 via sdccs __banked function keyword and custom banking trampoline code for the RTL837x in assembler.
-The following hardware is supported:
- Clock generation, including different divider settings
- Interrupt control for timer, serial, external irqs 0, 1
- Serial console via SFRs
- Flash operations via SFRs
- Bank switching via SFRs
- Access to Switch registers via SFRs
- LED setup
- Reset
- Some switch settings such as MAC configuration
- GPIO to detect SFP module insert/removal/RX-LOS
- I2C to read SFP EEPROM on 1 and 2 SFP slot devices
- NIC setup
- L2 learning table access, L2 table flushing
- VLAN setup/configuration
- Port mirroring
- Access to PHYs via MDIO (clause 45 via SFR):
- Internal PHYs of RTL8372 and RTL8373
- RTL8221 (1x2.5GBit port on devices with 5 ports)
- RTL8224 (4x2.5GBit ports on devices with 8 ports)
- SerDes settings of SoC via SFR:
- Configure SFPs with 10Gbit/2.5Gbit/1Gbit (Ethernet and Fiber SFP(+) tested)
- RTL8221, RTL8224
- NIC TX and RX of packets via SFRs
- send and receive Ethernet frames via SFRs and Switch registers
- RTL-tags and VLAN ingress-tag decoding for CPU-port
Ethernet frame RX IRQ via IRQ1 is conceptually understood, but not activated. RX is currently done via polling, which allows ping-times of <10ms.
The RTL8372/3 have 256 bytes of internal RAM (INTMEM) accessible through MOV instructions, which are used for the stack and important globals. Some of these are bit-adressable, e.g. for storing global flags.
Additionally, 64kB of extended RAM (XMEM) is built in, which is accessed through the MOVX instruction. It is used for global variables, for most of the function argument passing that is not done using the 8 registers R0-R7 or registers A/B, and for local variables (which requires extremely careful planning). The flash memory is transparently accessible for code being executed and can be used to store configuration. Access is done through the MOVC instruction, possibly setting the bank register before and resetting it to access the entire 4MB space. Code is prefetched from flash and cached in a small RAM automatically by the HW.
The peripherial functions are accessed through 2 different mechanisms:
- Special Function Registers (SFRs, 0x80-0xff) for banking, timers, UART, access to switch registers, MDIO, SPI (flash) and NIC transfers. Some SFRs are not used for HW purposes and can be used as RAM. Some SFRs are bit-adressable, allowing for very tight event wait loops (a single 2-byte instruction).
- 0x10000 switch registers, which appear to be very similar to the registers of the RTL838x, for which source code and datasheets are available. This controls clock dividers, GPIO/LEDs and general switch functionality.
The playground image shows access to the different types of memory using the SDCC compiler. Any support of Linux or e.g. Zephyr would require porting gcc. There are FreeRTOS ports to 8051 processors using sdcc, however.
Caution
NOTE THAT WHILE THIS PROCEDURE HAS BEEN SUCCESSFULLY TESTED ON ALL DEVICES ABOVE, ABSOLUTELY NO GUARANTY CAN BE GIVEN THAT YOU WILL NOT DESTROY YOUR SWITCH, ANY OTHER EQUIPMENT INVOLVED OR HARM YOURSELF BY OPENING THE ELECTRONIC DEVICE. OPENING THE SWITCH WILL VOID ITS WARRANTY.
There is no support for uploading the firmware via ethernet. Instead you need to open the switch and flash the image directly onto the flash chip, which is done easiest using a SOIC-8 clip (alternatively you de-solder the flash chip and install a SOIC adapter):
- Disconnect power from switch
- Attach the clip onto the flash chip
- Connect USB of flash programmer, the power LED on the switch will light up, check cabling if not. Don't panic, mixing up GND and 3.3V does not seem to destroy the switch (at leasts the on I did this to).
- Use IMSProg (flashrom should work, too) to detect the clip
- MAKE A BACKUP OF THE EXISTING FIRMWARE!
- then load the firmware into IMSProg
- and program flash
Now you can connect a serial cable to the UART port found on all the devices, set 8N1 @ 115200 baud and power up the switch.
The device will perform some examples and provide a minimal console, the documentation of which can be found in the source code rtlplayground.c`.
The command line is very rudimentary and mostly for testing purposes. The following is a boot-log with some examples:
Detecting CPU
RTL8373 detected
Starting up...
Flash controller
NIC reset
rtl8372_init called
RTL837X_REG_SDS_MODES: 0x00000bed
phy_config_8224 called
phy_config_8224 done
rtl8224_phy_enable called
rtl8224_phy_enable done
rtl8372_init done
A minimal prompt to explore the RTL8372:
CPU detected: RTL8373
Clock register: 0x00001101
Register 0x7b20/RTL837X_REG_SDS_MODES: 0x00000bed
Verifying PHY settings:
Port State Link TxGood TxBad RxGood RxBad
1 On Down 0x00000000 0x00000000 0x00000000 0x00000000
2 On Down 0x00000000 0x00000000 0x00000000 0x00000000
3 On Down 0x00000000 0x00000000 0x00000000 0x00000000
4 On Down 0x00000000 0x00000000 0x00000000 0x00000000
5 On 2.5G 0x00000008 0x00000000 0x00000000 0x00000000
6 On Down 0x00000000 0x00000000 0x00000000 0x00000000
7 On Down 0x00000000 0x00000000 0x00000000 0x00000000
8 On Down 0x00000000 0x00000000 0x00000000 0x00000000
9 NO SFP Down 0x00000000 0x00000000 0x00000000 0x00000000
> port 5 1g
CMD: port 5 1g
PORT 04 1G
> stat
CMD: stat
Port State Link TxGood TxBad RxGood RxBad
1 On Down 0x00000000 0x00000000 0x00000000 0x00000000
2 On Down 0x00000000 0x00000000 0x00000000 0x00000000
3 On Down 0x00000000 0x00000000 0x00000000 0x00000000
4 On Down 0x00000000 0x00000000 0x00000000 0x00000000
5 On 1000M 0x00000035 0x00000000 0x00000017 0x00000000
6 On Down 0x00000000 0x00000000 0x00000000 0x00000000
7 On Down 0x00000000 0x00000000 0x00000000 0x00000000
8 On Down 0x00000000 0x00000000 0x00000000 0x00000000
9 NO SFP Down 0x00000000 0x00000000 0x00000000 0x00000000
>
<SFP-RX OK>
<MODULE INSERTED> Rate: 67 Encoding: 01
Lightron Inc. WSPXG-ES3LC-IHA 0000
> stat
CMD: stat
Port State Link TxGood TxBad RxGood RxBad
1 On Down 0x00000000 0x00000000 0x00000000 0x00000000
2 On Down 0x00000000 0x00000000 0x00000000 0x00000000
3 On Down 0x00000000 0x00000000 0x00000000 0x00000000
4 On Down 0x00000000 0x00000000 0x00000000 0x00000000
5 On 1000M 0x00000065 0x00000000 0x0000003b 0x00000000
6 On Down 0x00000000 0x00000000 0x00000000 0x00000000
7 On Down 0x00000000 0x00000000 0x00000000 0x00000000
8 On Down 0x00000000 0x00000000 0x00000000 0x00000000
9 SFP OK 10G 0x00000000 0x00000000 0x0000001c 0x00000000
> sfp
CMD: sfp
Rate: 67 Encoding: 01
Lightron Inc. WSPXG-ES3LC-IHA 0000
Enjoy playing!
The following documents give further documentation on specific features of the RTL837x SoCs: