Hi,
Am Tue, Jun 22, 2021 at 11:07:17AM +0200 schrieb Ahmad Fatoum:
> Hi,
>
> On 22.06.21 10:35, Alexander Dahl wrote:
> > I just had a short look into u-boot for that board, there's the i2c
> > eeprom set in dts only, and dts is still the old u-boot way, not dts
> > from kernel plus fixups in a separate file. The mac is set in
> > board/atmel/sama5d27_som1_ek/sama5d27_som1_ek.c like this:
> >
> > 87 #define MAC24AA_MAC_OFFSET 0xfa
> > 88
> > 89 #ifdef CONFIG_MISC_INIT_R
> > 90 int misc_init_r(void)
> > 91 {
> > 92 #ifdef CONFIG_I2C_EEPROM
> > 93 at91_set_ethaddr(MAC24AA_MAC_OFFSET);
> > 94 #endif
> > 95 return 0;
> > 96 }
> > 97 #endif
> >
> > What would be the right way for kernel, u-boot, and barebox? Have i2c
> > eeprom defined in dts and an nvmem cell on top like you proposed for
> > barebox now?
>
> Many Linux network drivers already call of_get_mac_address and thus would
> read out a NVMEM cell if available. There aren't too many device trees
> making use of it, but that seems the preferred way going forward.
> (MAC addressed fixed up by bootloader is higher priority though).
>
> In general, I think Linux should not rely more than necessary on firmware.
>
> > Not sure if u-boot can do that (already)?
>
> No idea. grepping "mac-address" shows no nvmem related C code though.
FTR: grepping for "nvmem" in u-boot master matches in dts files and
binding docs only. There seems to be currently no code in u-boot
interpreting those dts nodes at all, no nvmem drivers.
> > But it would
> > still work if only Linux and barebox did it that way, right?
>
> So far, either board code set it, similar to your snippet above:
> eth_register_ethaddr(if_index, mac_addr);
>
> Or NVMEM drivers had a barebox,provide-mac-address = <&phandle_to_netdev ...>
> property and they called eth_register_ethaddr.
>
> The NVMEM binding is the upstream way, so after a device tree sync, even existing
> boards may find themselves with the correct address instead of randomization without
> having to do anything (nvmem cells doesn't override other methods, so no brekage).
Makes sense.
Greets
Alex
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