DESK-MX8M-L/Deployment/MAC Address programming
|1.0.0||Jun 2022||First release using DESK-MX8M-L-2.0.0-rc2|
- 1 MAC Address programming
- 1.1 Platform supported
- 1.2 Obtaining a MAC address
- 1.3 Permanent storage areas
- 1.4 MAC address programming on i.MX8M family
- 1.5 Linux kernel MAC address
MAC Address programming[edit | edit source]
Every network adapter has a Media Access Control address (usually shortened to MAC address). A MAC address is a six-byte identifying number permanently embedded in the firmware of the adapter, and is readable by the network and the operating system of the device on which the adapter is installed.
The address must follow the standards set by the Institute of Electrical and Electronics Engineers (IEEE), which sets computer networking standards.
The MAC address is a six-pair set of hexadecimal numbers, for example
a1-c2-e3-44-5f-6d. Specifically, in Ethernet, the MAC address is known as the Ethernet Address, which is the unique ID serial number of the Ethernet device in one's computer. MAC Addresses are used in a Local Area Network (LAN) by computers to communicate with each other. Every adapter has a unique MAC address.
Platform supported[edit | edit source]
In this Application Note, we will describe how to use the i.MX8M eFuse for programming and using the MAC address(es) and it applies to the following DAVE
i.MX8M family products:
This Application Note has been validated in the ORCA SOM. The commands used have been not validated in the other platform yet.
Obtaining a MAC address[edit | edit source]
To obtain a MAC address for your organization, please refer to our Setting the MAC address wiki page with the overall information about this topic.
Permanent storage areas[edit | edit source]
Some SOCs provide programmable OTPs for security, MAC address, boot modes, etc. Usually, some of these are general-purpose registers and can be managed by the user.
In other cases, an external permanent storage device can be used for storing permanent settings like the MAC address: for the i.MX8M product family, DAVE proposes to use the General Purposes eFuses (OTP blocks) on SoC itself for storing permanently the MAC address(es).
MAC address programming on i.MX8M family[edit | edit source]
MAC address configuration in u-boot[edit | edit source]
If the MAC address is not already programmed in the OTPs and the
ethaddr u-boot variable is not set, u-boot assignes a random value (different at every power on cycle):
Net: Warning: ethernet@30be0000 (eth0) using random MAC address - 6e:e5:6d:a2:ea:e5 eth0: ethernet@30be0000
ethaddr is set and saved in the u-boot environment, its value is used as the MAC Address:
u-boot=> setenv ethaddr 00:50:c2:1e:af:a8 u-boot=> saveenv Saving Environment to MMC... Writing to MMC(1)... OK u-boot=>
eFuse bank registers[edit | edit source]
i.MX8M family uses the Bank9 Word0, Word1 and Word2 (if the SoC has two ethernet interfaces) for storing the MAC addresses. The MAC values should be properly divided into the three registers for correct programming.
The related HW_OCOTP_MAC_ADDR0, HW_OCOTP_MAC_ADDR1, HW_OCOTP_MAC_ADDR2 OTP registers will be used for the purposes illustrated in this AN.
Warning!! eFuse programming is a permanent and non reversible action. Pay attention to the values and commands used during MAC programming.
eth0 eFuse programming[edit | edit source]
U-Boot uses the
fuse prog command for writing the MAC address into the eFuse. The MAC address should be divided in high 16 bit and low 32 bits, for example MAC address
AB:CD:12:34:56:78 for eth0 is then divided into :
fuse prog -y 9 0 0x12345678 fuse prog -y 9 1 0xABCD
In the following example the MAC address
00:50:c2:1e:af:a8 is stored in the SOC:
- (in case of presence) clear the
u-boot=> setenv ethaddr u-boot=> saveenv Saving Environment to MMC... Writing to MMC(1)... OK
- program the MAC address in the OPTs with the following commands:
u-boot=> fuse prog 9 0 c21eafa8 Programming bank 9 word 0x00000000 to 0xc21eafa8... Warning: Programming fuses is an irreversible operation! This may brick your system. Use this command only if you are sure of what you are doing! Really perform this fuse programming? <y/N> y u-boot=> fuse prog 9 1 0050 Programming bank 9 word 0x00000001 to 0x00000050... Warning: Programming fuses is an irreversible operation! This may brick your system. Use this command only if you are sure of what you are doing! Really perform this fuse programming? <y/N> y u-boot=>
If you want to write the eFuse value directly without confirmation, uses the
-y parameter with the
fuse prog command, as per the previous example:
u-boot=> fuse prog -y 9 0 c21eafa8 u-boot=> fuse prog -y 9 1 0050
At the next boot, the
ethaddr value wil be read from the OPTs:
Warning: ethernet@30be0000 using MAC address from ROM eth0: ethernet@30be0000 Fastboot: Normal Normal Boot Hit any key to stop autoboot: 0 u-boot=> print ethaddr ethaddr=00:50:c2:1e:af:a8 u-boot=>
The warning message informs that the
ethaddr is not present in the u-boot environment and it has been set using the value read from the OTPs. For clearing the warning, it is enough to save the environment with
eth1 eFuse programming[edit | edit source]
For the second ethernet interface, the above procedure should be repeated in a similar way, except of the correct eFuse register should be used:
The MAC address should be divided in low 16 bit and high 32 bits, for example MAC address
00:50:c2:1e:af:a9 is stored in the SOC using:
fuse prog -y 9 1 afa90000 fuse prog -y 9 2 0050c21e
Be Careful!! Register
eth1addr U-Boot variable is then used for the second ethernet interface MAC address management.
eFuse locking[edit | edit source]
The OTP eFuse registers should be locked in order to avoid unwanted registers (and then MAC addresses) modifications. OTP lock grants the MAC values cannot be modified anymore.
If not locked yet, OTP bits can be set to '1' but not reversed to '0' value, so some modifications can be applied if the eFuse registers are not locked.
For more information see, for example, the i.MX6 Dual Lite Reference Manual chap. 18.104.22.168
The two MAC addresses - even if sharing register
bank:9 word:1 - can be programmed at different times.
At the opposite, eFuse lock should be performed for both simultaneously. The registers lock can be forced using the following command:
fuse prog -y 0 0 c000
eFuse reading[edit | edit source]
The eFuse registers can be read - after programming - for checking the written values:
u-boot=> fuse read 9 0 Reading bank 9: Word 0x00000000: c21eafa8 u-boot=> fuse read 9 1 Reading bank 9: Word 0x00000001: afa90050 u-boot=> fuse read 9 2 Reading bank 9: Word 0x00000002: 0050c21e u-boot=>
Linux kernel MAC address[edit | edit source]
The MAC Address configured in u-boot is passed to the kernel which configures the
eth1 peripherals with the correct values:
root@desk-mx8mp:~# ifconfig eth0 Link encap:Ethernet HWaddr 00:50:c2:1e:af:a8 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) eth1 Link encap:Ethernet HWaddr 00:50:c2:1e:af:a9 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:43 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:82 errors:0 dropped:0 overruns:0 frame:0 TX packets:82 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:6220 (6.0 KiB) TX bytes:6220 (6.0 KiB) root@desk-mx8mp:~#