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

[David Antliff]

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:

ethernet at ff0e0000 {
    ...
    local-mac-address = [00 0a 35 00 22 01];
    ...

I would expect it to be 00 0a 35 07 60 1c based on the contents of the EEPROM.

I would like to understand how to debug this. I read that the command "eeprom" has been
deprecated for some time (I don't have it enabled), with some I2C serial EEPROM devices
now supported by the "Driver Model" - aka DM.

Thus I did find:

> dm uclass
...
uclass 39: i2c_eeprom
0     eeprom at 54 @ 7dd21420
...

And I'm able to communicate with the device via commands like:

ZynqMP> i2c md 54 0.2 40 200000 
0000: 5a 43 55 32 30 38 ff ff ff ff ff ff ff ff ff ff    ZCU208..........
0010: ff 41 30 32 38 33 32 32 30 34 31 34 33 33 32 38    .A02832204143328
0020: 31 2e 33 00 0a 35 07 60 1c 00 0a 35 07 60 1d 00    1.3..5.`...5.`..
0030: 0a 35 07 60 1e 00 0a 35 07 60 1f 41 08 ff ff ff    .5.`...5.`.A....

The MAC address is 6 bytes starting at offset 0x23 (00 0a 35 07 60 1c).

My question is - is the 'i2c' command now the accepted and best way to interact with an
I2C EEPROM? Or is there another command I can enable (other than "eeprom") that will
provide a generic interface for accessing EEPROMs and prove that U-Boot can "see" this
device?

The EEPROM device in question is an M24128.

CONFIG_SYS_I2C_EEPROM_ADDR=0x54
CONFIG_SYS_I2C_EEPROM_BUS=6
CONFIG_SYS_EEPROM_SIZE=16384
CONFIG_SYS_I2C_EEPROM_ADDR_LEN=2
CONFIG_ZYNQ_GEM_I2C_MAC_OFFSET=0x23
CONFIG_ZYNQ_MAC_IN_EEPROM=y

U-Boot 2021.01 (Xilinx fork: git://github.com/Xilinx/u-boot-xlnx.git)

P.S. if this is better directed to Xilinx or the Xilinx community then I'm happy to do that,
but in case it's a more generic U-Boot issue I thought it best to ask here first. Please
don't flame me for using Xilinx, I'm trying to do my best with what I'm given.

-- David.