[U-Boot] [PATCH 07/11] net: sunxi: Do not inject ethernet addresses into the env

[Olliver Schinagl]

Hey Hans,

I guess I have to contradict something here ...

On 15-11-16 11:17, Olliver Schinagl wrote:
> Hey Hans,
>
> I was hopeing and expecting this :)
>
>
> As you will be able to tell below, I need to learn a bit more as to why
> we do things and discuss this proper I guess.
>
>
> On 15-11-16 10:26, Hans de Goede wrote:
>> Hi,
>>
>> On 15-11-16 04:25, Joe Hershberger wrote:
>>> On Tue, Nov 8, 2016 at 9:54 AM, Olliver Schinagl <oliver at schinagl.nl>
>>> wrote:
>>>> Currently we inject 5 ethernet addresses into the environment, just in
>>>> case we may need them. We do this because some boards have no eeprom
>>>> (programmed) with a proper ethernet address. With the recent
>>>> addition of
>>>> reading actual ethernet addresses from the eeprom via the net_op we
>>>> should not inject environment variables any more.
>>>>
>>>> Signed-off-by: Olliver Schinagl <oliver at schinagl.nl>
>>>
>>> Acked-by: Joe Hershberger <joe.hershberger at ni.com>
>>
>>
>> Erm, this patch seems wrong to me: NACK, let me
>> explain:
>>
>> 1) It does not do what its commit message says, it only
>> removes the second step for setting ethernet addresses
>> from the env, but it keeps the existing code to set them
>> AFAICT, it only does it once now.
>>
>> 2) "Currently we inject 5 ethernet addresses into the environment",
>> this is not true, we only inject ethernet addresses into the
>> environment for devices which have an ethernet alias in dt,
>> so maximum 2 for devices with both wired ethernet and wifi
> If we want the fdt to do mac things, shouldn't that be done at a higher
> level? This is not really board specific is it?
>>
>> 3) The second attempt at setting ethernet addresses in
>> the environment after loading the kernel dt is necessary
>> because the kernel dt may be newer and contain more
>> ethernet aliases, e.g. the u-boot dt may only contain the
>> nodes + alias for the wired, while the (newer) kernel dt
>> may also contain a dt-node + alias for the wireless
> I agree with you here, but I still don't think this should be board
> specific
>>
>> 4) We cannot solely rely on the ethernet driver to set
>> mac-addresses, because the ethernet driver may not be enabled
>> while the kernel does have the ethernet driver enabled; and
>> the kernel relies on u-boot to generate fixed mac-addresses
>> based on the SID independent whether or not u-boot has
>> ethernet enabled, this is especially relevant for wifi
>> chips where the kernel also relies on u-boot generated
>> fixed mac-addresses on e.g. the recent orange-pi boards,
>> which come with a realtek rtl8189etv chip which does not
>> have a mac address programmed.
> I agree, and I'll fix that in my new patch series proper by making
> rtl8189etv also read rom hook which IS board specific

Of course I didn't realize that the rtl8189etv does not have a u-boot 
driver, and thus does not get to call its hook and thus nothing sunxi 
specific will ever be invoked.

So I guess in the case of the rtl8189 we have to figure out something 
(probably near the same as you did) to make it work.

It does feel somewhat nasty/hackish of course. I would expect that the 
linux driver sorts this out for itself and not simply assume u-boot 
supplies this info on non-existing hardware (to u-boot).

I need some time to think this over, so I'm hoping smarter people then 
me come with great suggestions here :)

But for now I'm leaning to think that, the rtl8189 is special.

So is this a board specific hack, or a fdt net specific hack. I does 
feel like the fdt bit I described earlier injects extra mac addresses 
into the environment for these unknown hardware pieces ... But that will 
need to come from board specific pieces, as the net stack never gets 
invoked for these ...

I'll stop thinking outloud now and get back to work ;)

olliver

>>
>> 5) AFAIK the dt code for passing mac-addresses to the kernel
>> relies on the environment variables, so even if we get the
>> mac-address from a ROM we should still store it in the
>> environment variable.
> The new patch series does that, as the net core layer does that.
>
> What happens is (note code is mangled and might not be 100% accurate, i
> reduced it the bares):
>
>     eth_read_eeprom_hwaddr(dev);
> first read from the eeprom, which may return all zero's if it is
> unconfigured/missconfigured or should not be used from the eeprom.
>     if (is_zero_ethaddr(pdata->enetaddr))
>         if (eth_get_ops(dev)->read_rom_hwaddr)
>             eth_get_ops(dev)->read_rom_hwaddr(dev);
> if the eeprom failed to produce a mac, we check the read_rom_hwaddr
> callback, which hooks into the driver. The driver can be overridden by a
> board (such as sunxi) where the MAC is generated from the SID.
>
> so at this point we may have a hwaddress actually obtained from the
> hardware, via the eeprom (or some fixed rom even) or from the hardware
> itself
> next we allow 'software' overrides. e.g. u-boot env (and i think this is
> where the fdt method should live as well
>
>     eth_getenv_enetaddr_by_index("eth", dev->seq, env_enetaddr);
>     if (!is_zero_ethaddr(env_enetaddr)) {
>         if (!is_zero_ethaddr(pdata->enetaddr) &&
>             memcmp(pdata->enetaddr, env_enetaddr, ARP_HLEN))
>                  memcpy(pdata->enetaddr, env_enetaddr, ARP_HLEN);
>
> // <snip> we compare the HW addr and the ENV addr. if the env is unset,
> we use whatever the hardware supplied us with.
> if the env is set, it overrides the HW addr.
> I think next would be to check the fdt to override the env?
>
>     } else if (is_valid_ethaddr(pdata->enetaddr)) {
>         eth_setenv_enetaddr_by_index("eth", dev->seq, pdata->enetaddr);
> Finally, we set whatever mac has come from the above probing into the
> environment (if the address is actually a valid MAC).
>
>     } else if (is_zero_ethaddr(pdata->enetaddr)) {
> #ifdef CONFIG_NET_RANDOM_ETHADDR
>         net_random_ethaddr(pdata->enetaddr);
> otherwise (if configured) let u-boot generate it.
>
>
> So I think here is where the fdt override should live, as it applies to
> everyone, not just sunxi.
>
> I'll post my split-up new series for review after testing it, so we can
> discuss it in more detail?
>
> Olliver
>>
>> Regards,
>>
>> Hans
>>
>

-- 
Met vriendelijke groeten, Kind regards, 与亲切的问候

Olliver Schinagl
Software Engineer
Research & Development
Ultimaker B.V.