[U-Boot] [PATCH v3] Retrieve MAC address from EEPROM

[Olliver Schinagl]

On 10-11-16 13:37, Michal Simek wrote:
> On 10.11.2016 13:31, Olliver Schinagl wrote:
>> On 10-11-16 13:26, Michal Simek wrote:
>>> On 10.11.2016 13:08, Olliver Schinagl wrote:
>>>> Hi Michal,
>>>>
>>>> On 10-11-16 12:37, Michal Simek wrote:
>>>>> On 8.11.2016 16:54, Olliver Schinagl wrote:
>>>>>> This patch-series introduces methods to retrieve the MAC address
>>>>>> from an
>>>>>> onboard EEPROM using the read_rom_hwaddr hook.
>>>>>>
>>>>>> The reason we might want to read the MAC address from an EEPROM
>>>>>> instead of
>>>>>> storing the entire environment is mostly a size thing. Our default
>>>>>> environment
>>>>>> already is bigger then the EEPROM so it is understandable that
>>>>>> someone might
>>>>>> not give up the entire eeprom just for the u-boot environment.
>>>>>> Especially if
>>>>>> only board specific things might be stored in the eeprom (MAC,
>>>>>> serial, product
>>>>>> number etc). Additionally it is a board thing and a MAC address
>>>>>> might be
>>>>>> programmed at the factory before ever seeing any software.
>>>>>>
>>>>>> The current idea of the eeprom layout, is to skip the first 8 bytes,
>>>>>> so that
>>>>>> other information can be stored there if needed, for example a header
>>>>>> with some
>>>>>> magic to identify the EEPROM. Or equivalent purposes.
>>>>>>
>>>>>> After those 8 bytes the MAC address follows the first macaddress. The
>>>>>> macaddress
>>>>>> is appended by a CRC8 byte and then padded to make for nice 8 bytes.
>>>>>> Following
>>>>>> the first macaddress one can store a second, or a third etc etc mac
>>>>>> addresses.
>>>>>>
>>>>>> The CRC8 is optional (via a define) but is strongly recommended to
>>>>>> have. It
>>>>>> helps preventing user error and more importantly, checks if the bytes
>>>>>> read are
>>>>>> actually a user inserted address. E.g. only writing 1 macaddress into
>>>>>> the eeprom
>>>>>> but trying to consume 2.
>>>>>>
>>>>>> Hans de Goede and I talked about retrieving the MAC from the EEPROM
>>>>>> for sunxi
>>>>>> based boards a while ago, but hopefully this patch makes possible to
>>>>>> have
>>>>>> something slightly more generic, even if only the configuration
>>>>>> options.
>>>>>> Additionally the EEPROM layout could be recommended by u-boot as well.
>>>>>>
>>>>>> Since the Olimex OLinuXino sunxi boards all seem to have an eeprom, I
>>>>>> started
>>>>>> my work on one of these and tested the implementation with one of our
>>>>>> own real
>>>>>> MAC addresses.
>>>>>>
>>>>>> What still needs disussing I think, is the patches that remove the
>>>>>> 'setup_environment' function in board.c. I think we have put
>>>>>> functionality in
>>>>>> boards.c which does not belong. Injecting ethernet addresses into the
>>>>>> environment instead of using the net_op hooks as well as parsing the
>>>>>> fdt to get
>>>>>> overrides from. I think especially this last point should be done at
>>>>>> a higher
>>>>>> level, if possible at all.
>>>>>>
>>>>>> I explicitly did not use the wiser eth_validate_ethaddr_str(),
>>>>>> eth_parse_enetaddr() and the ARP_HLEN define as it was quite painful
>>>>>> (dependancies) to get these functions into the tools. I would suggest
>>>>>> to merge
>>>>>> as is, and if someone wants to improve these simple tools to use
>>>>>> these functions
>>>>>> to happily do so.
>>>>>>
>>>>>> These patches where tested on Olimex OLinuXino Lime1 (A10/A20), Lime2
>>>>>> (NAND
>>>>>> and eMMC) and A20-OLinuXino-MICRO-4G variants and have been in use
>>>>>> internally on our production systems since v2 of this patch set.
>>>>>>
>>>>>> As a recommendation, I would suggest for the zynq to adopt the config
>>>>>> defines,
>>>>>> as they are nice and generic and suggest to also implement the 8 byte
>>>>>> offset,
>>>>>> crc8 and pad bytes.
>>>>> Yes, Zynq and ZynqMP is using this feature. I am also aware about using
>>>>> qspi OTP region for storing information like this.
>>>> I saw, which triggered me here. What the Znyq currently does it uses its
>>>> own private CONFIG setting:
>>>>
>>>> +int zynq_board_read_rom_ethaddr(unsigned char *ethaddr)
>>>> +{
>>>> +#if defined(CONFIG_ZYNQ_GEM_EEPROM_ADDR) && \
>>>> +    defined(CONFIG_ZYNQ_GEM_I2C_MAC_OFFSET) && \
>>>> +    defined(CONFIG_ZYNQ_EEPROM_BUS)
>>>> +       i2c_set_bus_num(CONFIG_ZYNQ_EEPROM_BUS);
>>>> +
>>>> +       if (eeprom_read(CONFIG_ZYNQ_GEM_EEPROM_ADDR,
>>>> +                       CONFIG_ZYNQ_GEM_I2C_MAC_OFFSET,
>>>> +                       ethaddr, 6))
>>>> +               printf("I2C EEPROM MAC address read failed\n");
>>>> +#endif
>>>> +
>>>> +       return 0;
>>>> +}
>>>>
>>>> which are ZNYQ specific. In my patchset I give them very generic names
>>>> as they can be used by anybody really.
>>>>
>>>> Once Maxime's patches have merged and stabilized, i'd even say to switch
>>>> over to the eeprom framework.
>>> Can you give me that link to these patches?
>> Well [0] is your own patch, so that is easy :) [1] is Maxime's work. But
>> with your generic comment, this entire function probably can simply go
>> then. The only thing I haven't figured out/thought through yet, if
>> eeprom reading fails, we want to fall back to the old board specific
>> method. But I think I know what might do there ...
> Joe recently applied one our patch
> http://lists.denx.de/pipermail/u-boot/2016-November/271662.html
> which in case of NET_RAMDOM_ETHADDR generates random address.
> I don't have in my mind exact calling sequence but I expect when eeprom
> read failed then random eth is generated if selected or warning, etc.
In the case of sunxi, we generate a MAC address based off the CPU serial 
number and device ID, which is more predictable and doesn't change 
compared to the random MAC. The random MAC would then in turn be a 
fallback if we still have a 00:00:00:00:00 ethernet address.

So 3 steps, check EEPROM (i2c only for now, SPI etc can be added later 
with the eeprom uclass)
call board specific hook
if empty, generate random (if configured)

>
> Thanks,
> Michal
>
>