Setting MAC address from I2C EEPROM - debug / commands? (Xilinx)

[David Antliff]

Hi Michal,

On 23 Nov 2022, Michal Simek wrote:
>> On 11/23/22 04:14, Sean Anderson wrote:
>>> On 11/22/22 20:23, David Antliff wrote:
>>> Hi,
>>>
>>> I'm looking to extract the board's MAC address from serial I2C EEPROM at boot
>>> time, so
>>> I'm trying to work out how I can tell if U-Boot is actually able to
>>> communicate with this
>>> EEPROM, outside of manual i2c commands.
>>>
>>> I have set CONFIG_ZYNQ_MAC_IN_EEPROM and CONFIG_ZYNQ_MAC_IN_EEPROM
>>> however I'm not completely sure that this is working with UltraScale+ Zynq MPSoC
>>> boards - I'm using a ZCU208. There's no log message on the U-Boot console to say
>>> that there was an attempt to read the MAC address, and with ethaddr unset, this
>>> variable is set by U-Boot to the value taken from the device tree rather than
>>> EEPROM:
>
> That was the old way how to this was achieve and based on DTS in the mainline it
> is not used on any existing board because none defined xlnx,eeprom property.
> 
> I just sent the patch to remove also Kconfig entries which we forget to clean up.
>
> But the way how it is working now is that eeprom is referenced by nvmem alias.
> You can find conversion here
> 531abcb71e60 ("xilinx: Convert xlnx,eeprom property to nvmem alias")
>
> Then you have nvmem link to eeprom which can be used.
> 
> In board_init() you can see calling xilinx_read_eeprom() which reads this link.
>
> This structure was added for FRU format decoding also with supporting legacy
> format used on zcu1xx boards.
>
> IIRC zcu208 is not using legacy format used on zcu1xx boards
> xilinx_read_eeprom_legacy() and there is one more legacy format which is not
> currently supported by this code.
> But it shouldn't be that complicated to add support for it because it is pretty
> much just different layout.
>
>That's why I am suggesting you to create that nvmem0 link and take a look at
> that format to support.
>
> Then mac address is saved to environment variables and used by ethernet driver.

Thank you for your advice - if I were using a newer version of U-Boot I would certainly
look into this. Please see my reply to Sean for what I ended up doing, which is obviously
prior to any nvmem-cells support, and uses the old Kconfig options and xlnx,eeprom.

I'm using PetaLinux 2021.2, but I note that in the 2022.1 changelog there is this:

    U-Boot: Added support for reading MAC address from multi-record FRU data in EEPROM

Unfortunately until I have a chance to update my version of PetaLinux, I am unable
to test or contribute to the head of U-Boot. Thank you for your help though. This all adds
context to what I'm doing, and makes me think I really should figure out how to update to a
newer version of U-Boot sooner rather than later.

-- David.